From: Edward Cranswick <cranswick@........>
Subject: Re: Thrust animation
Date: Mon, 31 Mar 1997 13:50:08 -0700
Charles
> Gosh, this animation stuff has a lot of potential.
The graphics are cool, but you have the fault displacing at the surface
before any seismic waves, indicated by the expanding concentric circles,
get there -- which they never do anyway. Seismic waves are the way the
that information about the state -- stress and strain -- of the Earth is
propagated, and there can be no deformation prior to propagation.
-Edward
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Thrust animation
Date: Mon, 31 Mar 1997 14:16:05 -0700
Charles-
Notwithstanding my previous comment, I think that the break off of the
thrust block with attendant trees down the scarp is a nice touch. It is
very realistic and an appropriate reminder to geophysicists that the
Earth is more than a homogeneous halfspace or a sphere.
-Edward
> I used the new Macromedia Freehand 7.0 to make the graphic and just
> nudged the hanging wall block up a few knotches before saving it each
> time as a tiff file. Had to throw a few white blocks in blot out the
> background behind the trees and to size the top of the graphic. And just
> for fun, I had the nose of the thrust block break off and send tree and
> a bunch of dirt down the scarp for the final frame.
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: Thrust animation
Date: Mon, 31 Mar 1997 12:39:37 -0900
Charlie,
I like the animation. Check out the EQ animation of Tau Rho that
I converted to quick time at:
http://www.giseis.alaska.edu/Input/lahr/taurho/eqeffects/introduction.html
I would like to have an animation that shows the elastic rebound:
slow bending followed by rupture. I've tried a bit on this but my
artwork is not very good.
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Correction Correction!!!!
Date: Mon, 31 Mar 1997 13:57:50 -0900
I've been looking at the location of the recent earthquakes
incorrectly! They are East and not West longitude, so occur
within the eastern end of the 1965 Rat Islands earthquake zone,
not within the western end of the 1957 break. Sorry for the
confusion on my part. I've made some corrections below.
>
> The continuing activity in the Rat Islands is quite interesting.
>
> This portion of the arc was ruptured by an MW 8.6 earthquake in 1957
> which allowed a 900 km-wide portion of the Pacific plate to subduct
> a bit deeper beneath the Bearing Sea, which is part of the North
> American Plate.
>
> In 1986 a 225-km wide portion of the 1957 zone located south and east
> of Adak Island broke again in a magnitude MW 8.0 event. This
> left two portions of the 1957 break still unbroken: a 175-km wide
> zone on the west and a 500-km wide zone on the east.
>
> On June 10, 1996, a magnitude MW 7.9 earthquake extended the
> reruptured portion of the 1957 break another 125-km to the west,
> possibly falling short by about 50 km from rupturing all the way to
> the western limit of the 1957 break.
>
The recent MW 6.6 event on March 26 at 02:08 UT and its aftershocks
are located very near the eastern limit of the 1965 rupture zone,
which is the next large break (MW 8.7) west of the 1957 zone.
What does this portend for rerupture of the 1965 zone? What about
rerupture of the eastern portion of the 1957 zone? Stay tuned to
see what happens.
(To be continued, on a geologic time scale.)
JCLahr
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: Rat Islands Earthquakes
Date: Mon, 31 Mar 1997 04:47:13 -0800
John,
It was my understanding the 1957 Mw 9.1 earthquake ruptured the
Andreanof and the western Fox Islands segemnts and the 1965 M8.2
earthquake ruptured the Rat and Near Islands segments.
By looking at the aftershock pattern from the June 10 Mw 7.9 and Mw 7.2
earthquakes ruptured the western portion of the Andreanof segment from
174W-179W (central Atka Is. to just west of Amatignak Island) (See
Seismo-Watch Newsletter Vol. 4 No. 25. The aftershocks suggest the 1957
rupture extended at least to Amatignak Island and more likely past
Amchitka Passage to Amchitka Island.
The 1965 Rat Islands earthquake was centered pretty darn close to
Amchitka Island and part of it may have extended eastward into Amchitka
passage and into the 1957 rupture zone.
The recent Mw 6.6 earthquake was centered about 12 miles east of a M6.4
event a year and two days ago.
What is interesting is the Komdandorsky segment which has not ruptured
in historic times. Every now and again it releases a M5 and creates a
stir amoung the Seismo betting tables - an in house thing here at
Seismo-Watch.
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
Dr. John Lahr (USGS-GI Seismologist) wrote:
>
> The continuing activity in the Rat Islands is quite interesting.
>
> This portion of the arc was ruptured by an MW 8.6 earthquake in 1957
> which allowed a 900 km-wide portion of the Pacific plate to subduct
> a bit deeper beneath the Bearing Sea, which is part of the North
> American Plate.
>
> In 1986 a 225-km wide portion of the 1957 zone located south and east
> of Adak Island broke again in a magnitude MW 8.0 event. This
> left two portions of the 1957 break still unbroken: a 175-km wide
> zone on the west and a 500-km wide zone on the east.
>
> On June 10, 1996, a magnitude MW 7.9 earthquake extended the
> reruptured portion of the 1957 break another 125-km to the west,
> possibly falling short by about 50 km from rupturing all the way to
> the western limit of the 1957 break.
>
> The recent MW 6.6 event on March 26 at 02:08 UT and its aftershocks
> are located very near the western limit of the 1957 rupture zone.
> Is this it for the western end of the 1957 break, or will there
> be more action in the near future? What about rerupture of
> the eastern portion of the 1957 zone? Stay tuned to see what
> happens.
>
> (To be continued, on a geologic time scale.)
>
> JCLahr
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Thrust animation
Date: Mon, 31 Mar 1997 20:49:46 -0700
John-
> I like the animation. Check out the EQ animation of Tau Rho that
> I converted to quick time at:
I downloaded your file and the Quicktime plug-in for Win 95/NT for the
Netscape 3.0 browser I use, but the graphics were wierd -- coarse and
black -- though there was some heavy duty sounds ... I don't know
whether that was live or Memorex, i.e., my machine or your file or both.
-Edward
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: more Grizzly Island swarm
Date: Wed, 02 Apr 1997 10:00:12 -0800
....and the Grizzly Island swarm in the San Francisco Delta continues.
Five M2+ events in the last two days, including a pair of M3s. The
largest registered M3.4.
...and just when your thought it had gone away...
4 guines for a M4+? Ante up!
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Dennis Leatart <ASTROSEEK@.........>
Subject: large quake?
Date: Fri, 04 Apr 1997 11:36:30 -0800
Hi to all!!!
Did any of you pick up a quake about 9:30 UT on 4/4/97 (1:30PST)?? I
have a large classic trace at that time, but it does not correspond to
the 5.0 or 4.9 in Central America-- this was the only match I could find
on the net??
--
_____ __
| \.-----.-----.-----.|__|.-----.
| -- | -__| | || ||__ --|
|_____/|_____|__|__|__|__||__||_____|
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Re: large quake?
Date: Fri, 04 Apr 1997 12:58:03 -0800
At 11:36 AM 4/4/97 -0800, Dennis Leatart wrote:
>Did any of you pick up a quake about 9:30 UT on 4/4/97 (1:30PST)?? I
>have a large classic trace at that time, but it does not correspond to
>the 5.0 or 4.9 in Central America-- this was the only match I could find
>on the net??
Hi Dennis --
I saw it too. It was a ML3.3 in Inglewood, CA...
The following is from http://scec.gps.caltech.edu/cgi-bin/finger?quake, the
Southern California Earthquake Report.
97/04/04 09:26:24 33.98N 118.35W 4.2 3.3MLG A 1 mi. N of INGLEWOOD
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: geophones
Date: Mon, 07 Apr 1997 22:12:33 -0700
David A Nelson wrote:
>
> hi all,
> below is a reply I received from the Geo Space Corp. It may be
> of general interest
> Their homepages at http://www.geospacecorp.com/ have photos of the
> GS-20DX geophone
>
> At a resonance of 8Hz I wonder if the info that it would give for
> regional quakes US$22.00 is a great price worth the experimentation I
> think ???
>
> the other unit (GS-11D) is not listed on their pages only in the e-mail
> to me at 4.5Hz it is the same as the ones I am using at home in Dunedin
> and at US$60 is a good option for a precision short period seismometer.
>
> for your thoughts Dave
>
Hi Dave-
I have also inquired about freq. response and cost. Normally if you
are measuring displacement you want the natural freq of the sensor to be
lower than the lowest freq monitored. If you are measuring acceleration
you want the sensors natural freq to be higher than the highest freq
measured. I'm not sure if these sensors are force balance or not.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: geophones
Date: Tue, 08 Apr 1997 19:44:45 +1200
Barry,....
ok on your thoughts, I am already using 4.5 Hz geophones at home
and as a short period seismometer they are perfect with excellent detection
of regional events.
I have recorded many large events in the 1500 km + (eventually when
my LP unit is working the distant events will be recorded much better)
Since posting the original mail I have placed an order with Geo Space Corp.
for 1 x GS20-DX, 8 Hz unit and 3 x GS11-D, 4.5 Hz units. This company's
prices were better than any other quotes that I received, for a virtually
identical unit. It will be interesting to see the response of the 8 Hz
seismometer when recording regional events.
I don't know if they are forced balanced or not either as I don't
really know the definition of what is meant by forced balance????.
Dave
Barry, you wrote
>Hi Dave-
> I have also inquired about freq. response and cost. Normally if you
>are measuring displacement you want the natural freq of the sensor to be
>lower than the lowest freq monitored. If you are measuring acceleration
>you want the sensors natural freq to be higher than the highest freq
>measured. I'm not sure if these sensors are force balance or not.
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: geophones
Date: Tue, 08 Apr 1997 20:52:29 -0600
A velocity sensor (a geophone, i.e., a damped harmonic oscillator with a
velocity transducer sensing pendulum motion) will have a flat frequency
response to (output voltage will be proportional to) ground velocity
above the natural frequency, and its response will decay (decrease) at
12 dB per octave (2-pole; proportional to frequency squared: 1/f^2)
below the natural frequency, i.e., it acts as a high-pass filter. By
the same token, the pendulum motion will have the same response to
acceleration and displacement, i.e., the acceleration and displacement
responses of the pendulum (assuming one has a way of sensing the
acceleration or displacement motion of the pendulum directly) will be
flat above the natural frequency and equivalently decay below the
natural frequency. Actually, a velocity sensor exhibits a higher, or
upper, resonant frequency caused by the inductance response of the
velocity sensor coil interacting with the magnetic field. This produces
a 6 dB per octave (1-pole) decay above the upper resonant frequency,
i.e., it acts like a low-pass filter, that is characteristically one to
orders of magnitude above the natural freqency. For example, the Marks
Products L-22 geophone has a 2.0 Hz natural frequency and an 85.0 Hz
upper frequency.
Barry Lotz wrote:
>
> David A Nelson wrote:
> >
> > hi all,
> > below is a reply I received from the Geo Space Corp. It may be
> > of general interest
> > Their homepages at http://www.geospacecorp.com/ have photos of the
> > GS-20DX geophone
> >
> > At a resonance of 8Hz I wonder if the info that it would give for
> > regional quakes US$22.00 is a great price worth the experimentation I
> > think ???
> >
> > the other unit (GS-11D) is not listed on their pages only in the e-mail
> > to me at 4.5Hz it is the same as the ones I am using at home in Dunedin
> > and at US$60 is a good option for a precision short period seismometer.
> >
> > for your thoughts Dave
> >
> Hi Dave-
> I have also inquired about freq. response and cost. Normally if you
> are measuring displacement you want the natural freq of the sensor to be
> lower than the lowest freq monitored. If you are measuring acceleration
> you want the sensors natural freq to be higher than the highest freq
> measured. I'm not sure if these sensors are force balance or not.
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Fox Island Event(?)
Date: Tue, 08 Apr 1997 20:26:21 -0700
Hi Everyone,
I just uploaded to Larry's machine an event I recorded at about 15:20 UT
today (4/8/97). I think it must be the Fox Island event, but nothing seems
to quite match the USGS report. -- The time, distance, and magnitude don't
seem quite right.
Anyone else see this event, and do your numbers match the USGS's better
than mine?
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ct@....... (Charlie & Terri Thompson -- @MicroRanch )
Subject: Re: Fox Island Event(?)
Date: Tue, 08 Apr 1997 23:02:28 -0500
I have an un-matched event estimated origin time of 15:24 UTC 4/8.
Fox Island seems too far away. If I ID'ed the P and S correctly
it's less than 1000 miles from Buda, Texas..probably Mexico..
shallow quake with large surface wave estimated Ms5.5.
Anybody else bag this event?
-Charlie Thompson
Buda, Texas
>Hi Everyone,
>
>I just uploaded to Larry's machine an event I recorded at about 15:20 UT
>today (4/8/97). I think it must be the Fox Island event, but nothing seems
>to quite match the USGS report. -- The time, distance, and magnitude don't
>seem quite right.
>
>Anyone else see this event, and do your numbers match the USGS's better
>than mine?
>
>
>Karl Cunningham
>La Mesa, CA.
>karlc@.........
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
_____________________________________________________________________
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From: Barry Lotz <gbl@.......>
Subject: Re: geophones
Date: Tue, 08 Apr 1997 21:20:18 -0700
Edward Cranswick wrote:
>
> A velocity sensor (a geophone, i.e., a damped harmonic oscillator with a
> velocity transducer sensing pendulum motion) will have a flat frequency
> response to (output voltage will be proportional to) ground velocity
> above the natural frequency, and its response will decay (decrease) at
> 12 dB per octave (2-pole; proportional to frequency squared: 1/f^2)
> below the natural frequency, i.e., it acts as a high-pass filter. By
> the same token, the pendulum motion will have the same response to
> acceleration and displacement, i.e., the acceleration and displacement
> responses of the pendulum (assuming one has a way of sensing the
> acceleration or displacement motion of the pendulum directly) will be
> flat above the natural frequency and equivalently decay below the
> natural frequency. Actually, a velocity sensor exhibits a higher, or
> upper, resonant frequency caused by the inductance response of the
> velocity sensor coil interacting with the magnetic field. This produces
> a 6 dB per octave (1-pole) decay above the upper resonant frequency,
> i.e., it acts like a low-pass filter, that is characteristically one to
> orders of magnitude above the natural freqency. For example, the Marks
> Products L-22 geophone has a 2.0 Hz natural frequency and an 85.0 Hz
> upper frequency
Put another way:
What I was refering to was(For damping around 0.7): For long period
sensors, the deflection of the sensor would measure the ground
deflection and be flat for frequencies above the sensor's natural
frequency and decay for frequencies lower. For short period sensors, the
sensor's deflection would represent the ground acceleration and would be
flat for frequencies below the sensor's natural frequency and decay for
frequencies above the sensors natural frequency; ie, turning a
acceleromometer on it side(low frequency) induces a 1G acceleration but
is evidenced by the sensor deflecting.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Exploration Geophones
Date: Wed, 9 Apr 1997 12:17:16 -0800
Arlen,
Here's the revised text from http://www.giseis.alaska.edu/Input/lahr/web.sites.html:
"Arlen Juels of Seistex '86, Inc. has a number of used seismic refraction
geophones that he is willing to provide to teachers for the cost of
shipping. He can be contacted at AJuels@......... These are relatively
high frequency phones (mostly 8 to 14 Hz vertical) that are small and well
suited to "table-top" seismology. Due to their poor response to frequencies
below 8 Hz, these phones are not ideally suited for earthquake monitoring,
but would respond to very nearby earthquakes."
I'll cc this message to the amateur seismologists of the Public Seismic Network
to let them know of your offer, so you may get some requests from them too.
Thanks again for you generousity,
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: geophones
Date: Wed, 09 Apr 1997 15:45:01 -0600
Barry-
I completely with you agree that the displacement response, i.e., the
deflection, is proportional to ground acceleration for frequencies below
the natural frequency and to ground displacement above the natural
frequency.
-Edward
Barry Lotz wrote:
> What I was refering to was(For damping around 0.7): For long period
> sensors, the deflection of the sensor would measure the ground
> deflection and be flat for frequencies above the sensor's natural
> frequency and decay for frequencies lower. For short period sensors, the
> sensor's deflection would represent the ground acceleration and would be
> flat for frequencies below the sensor's natural frequency and decay for
> frequencies above the sensors natural frequency; ie, turning a
> acceleromometer on it side(low frequency) induces a 1G acceleration but
> is evidenced by the sensor deflecting.
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: geophones
Date: Wed, 09 Apr 1997 15:55:50 -0600
George-
Though I am not very familiar with the Lehmans used by many of the
PSN, I think you have raised an excellent point, or rather, have made a
very insightful inference. In 1975, when I was in graduate school for
seismology, I read an interesting paper for an instrumentation seminar
that described various cross-coupling phenomena, including the tilt
effect you surmise, that long-period seismometers are subject to. I do
not have the reference to the paper handy, but it should be out there
somewhere.
-Edward
George A. Harris wrote:
>
> Ed,
> I have been monitoring the PSN newsgroup for some time, and have been
> running a displacement seismometer during the quakes in Russia and
> the far east last year. I have a question.
>
> My seismometer was a displacement unit which caught the 16 second
> period signals from the distant quakes. Since the natural mechanical
> frequency of the unit was near 1 hz., I have become suspicous that
> the unit is actually measuring tilts rather than lateral accelerations.
> Do you agree? If so it might be useful to discuss this on the
> mailgroup.
>
> George Harris
>
>
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: owl@............
Subject: Is Your Web Site A Secret?
Date: Thu, 10 Apr 1997 07:14:59 -0400 (EDT)
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Email: owl@............
HOW DO I ORDER?
The easiest way to order is by e-mail. Just hit the REPLY button on
your e-mail program and fill out the following information. (This
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Key words (maximum of 25, in descending order of importance):
Proofs (Where shall we e-mail proofs):
If billing a different address, please complete the following:
Addressee:
Company Name:
Address:
City: State/Prov: Zip/Postal Code:
Telephone:
Fax:
Email address:
We will bill via Email. (7310)
Terms: By returning this document via Email, you agree as follows:
You have the authority to purchase this service on behalf of your
company. Terms are net 15 days. Accounts sent to collections will
be liable for collection costs. You agree to protect and indemnify
Owl's Eye Productions, Inc. in any claim for libel, copyright
violations, plagiarism, or privacy and other suits or claims based on
the content or subject matter of your site.
WHAT HAPPENS NEXT?
When we receive your order, we will input the information into
our system, and send you a proof.
After we process any corrections, we will run your promotion, capturing
any comments from search engines as we go. We will incorporate these
into an HTML-formatted report to you, which we will attach to
your bill.
===Web Promotions=====Press Releases=====Link Exchanges=========
Owl's Eye Productions, Inc.
260 E. Main Street
Brewster, NY 10509
Ph: 914-278-4933 Fx: 914-278-4507 E-mail: owlseye@............
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: owl@............
Subject: Is Your Web Site A Secret?
Date: Thu, 10 Apr 1997 07:14:54 -0400 (EDT)
Is your web site the best kept secret on the Internet?
We'll promote it to 50 search engines and indexes for $85
and complete the job in 2 business days. Satisfaction is
guaranteed!
If you have a great product, but are not getting many inquiries from
your Web site, you may not be adequately listed on the Web's search
engines and indexes.
Millions of viewers daily use these facilities to find the products
and services they are looking for. But if your site is not listed, no
one will see it.
Listings on most of these services are free. However, locating and
filling out the forms required to get a listing can take several days,
and most people just don't have the time to do it.
That is why we offer a web site promotion service.
WHAT'S THE DEAL?
We will submit your site to 50 indexes and search engines for $85. We
will accept the return of this E-mail, with the form below filled out,
as an order. We will bill you upon completion of the promotion. Our
terms are net 15 days from date of invoice. Satisfaction guaranteed!
HOW LONG WILL IT TAKE?
Generally, we complete the submissions within 48 hours of
receiving your order. It can take any individual search engine or
index up to three weeks to process your submission, although most are
much faster.
WHAT SEARCH ENGINES AND INDEXES ARE INCLUDED IN THE
PROMOTION?
The list changes from time to time. This is our current list:
Abaweb!, Alta Vista, Been There, BizWeb, Central Source Yellow Pages,
Enterpreneurs on the Web, Excite, Four11, Galaxy, I-Network I-Systems
Spiral Business Directory, I-World Web Pointer, Infoseek, Inktomi,
Innovator's Network Yellow Pages, Internet Mall, Jayde Online Directory,
Jumpcity, Jumper Hot Links, Linkmaster, Lycos, Magellan, Mega Mall,
Net-Happenings, Net Navigator, Net Mall, NTG's List, NYNEX Big Yellow,
One World Plaza, OnLine's WWWeb Index, Rex, Starting Point, Truenorth,
URL Tree, Virtual Lynx, Web Point, WebCentral, Web Venture Hotlist,
Webcrawler, Websurf, Win Mag/NetGuide Hotspots, WhatUSeek, Worldwide
Announce Archive, WWW Business Yellow Pages, World Wide Yellow Pages,
WWW Worm, YelloWWWeb.
HOW WILL I KNOW THAT YOU HAVE PROMOTED MY SITE?
When we have completed the promotion, we will send you an HTML
file as an attachment to your E-mail bill. Save this file to your
disk, and view it through your Web browser. It provides links to the
search engine we submitted your site to, plus any comments we received
from them when we did it.
ARE THERE ANY GUARANTEES?
We do not require prepayment. Your satisfaction is guaranteed or
you don't pay the bill.
WHO IS OWL'S EYE PRODUCTIONS?
We are a web site promotion company located at:
Owl's Eye Productions, Inc.
260 E. Main Street
Brewster, NY 10509
Phone: (914) 278-4933
Fax: (914) 278-4507
Email: owl@............
HOW DO I ORDER?
The easiest way to order is by e-mail. Just hit the REPLY button on
your e-mail program and fill out the following information. (This
information will be posted to the search engines/indexes):
Your name:
Company Name:
Address:
City: State/Prov: Zip/Postal Code:
Telephone:
Fax:
Email address:
URL: http://
Site Title:
Description (about 25 words):
Key words (maximum of 25, in descending order of importance):
Proofs (Where shall we e-mail proofs):
If billing a different address, please complete the following:
Addressee:
Company Name:
Address:
City: State/Prov: Zip/Postal Code:
Telephone:
Fax:
Email address:
We will bill via Email. (7310)
Terms: By returning this document via Email, you agree as follows:
You have the authority to purchase this service on behalf of your
company. Terms are net 15 days. Accounts sent to collections will
be liable for collection costs. You agree to protect and indemnify
Owl's Eye Productions, Inc. in any claim for libel, copyright
violations, plagiarism, or privacy and other suits or claims based on
the content or subject matter of your site.
WHAT HAPPENS NEXT?
When we receive your order, we will input the information into
our system, and send you a proof.
After we process any corrections, we will run your promotion, capturing
any comments from search engines as we go. We will incorporate these
into an HTML-formatted report to you, which we will attach to
your bill.
===Web Promotions=====Press Releases=====Link Exchanges=========
Owl's Eye Productions, Inc.
260 E. Main Street
Brewster, NY 10509
Ph: 914-278-4933 Fx: 914-278-4507 E-mail: owlseye@............
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Michael J. Roseberry" <roseberry@...........>
Subject: Re: Is Your Web Site A Secret?
Date: Thu, 10 Apr 1997 11:10:57 -0500
owl@............ wrote:
>
> Is your web site the best kept secret on the Internet?
>
> We'll promote it to 50 search engines and indexes for $85
> and complete the job in 2 business days. Satisfaction is
> guaranteed!
>
> snip ...
Have we been invaded? :-|
Michael J. Roseberry
--
_____________________
roseberry@...........
mjr@........
"There is no good substitute for understanding." -- mjr
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: arrival time calculator
Date: Thu, 10 Apr 1997 11:54:58 -0800
Charlie,
Thank you for pointing out that my arrival time calculator
page (http://www.giseis.alaska.edu/Input/lahr/artim.html)
was not working for NEIC finger events.
I found a bug I had introduced the other day when I added
spyder events, neic accumulated events, etc. Everything worked
except the standard NEIC finger! Reload and try it again now.
Write back if you stop any other problems. Microsoft isn't
the only one that depends on user feedback.
Cheers,
JCLahr
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Is Your Web Site A Secret?
Date: Thu, 10 Apr 1997 12:57:51 -0700
At 11:10 AM 4/10/97 -0500, you wrote:
>owl@............ wrote:
>>
>> Is your web site the best kept secret on the Internet?
>>
>> We'll promote it to 50 search engines and indexes for $85
>> and complete the job in 2 business days. Satisfaction is
>> guaranteed!
>>
>> snip ...
>
>
>Have we been invaded? :-|
Sure have, I sent a nasty note to owl@. I also did a whois and found the
contact person for the domain so I also sent the note to john@.............
Feel free to write your own note to the email spammers letting them know
what you think of them. Make sure and send the message directly to them and
not the list. I also contacted there ISP at postmaster@....... letting them
know one of there accounts is spamming email. Later tonight I will call the
number at the bottom of the message and leave a nasty voice mail message.
I will also make a change to my mail server so email from olwsnest.com will
not go out.
Regards,
Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Lucas Haag <lhaag@..............>
Subject: Re: Is Your Web Site A Secret?
Date: Thu, 10 Apr 97 16:09:41 CDT
THANK YOU LARRY! I'm sure that you efforts are appricated by all of the
members of the mailing list.
At 12:57 PM 4/10/97 -0700, you wrote:
>At 11:10 AM 4/10/97 -0500, you wrote:
>>owl@............ wrote:
>>>
>>> Is your web site the best kept secret on the Internet?
>>>
>>> We'll promote it to 50 search engines and indexes for $85
>>> and complete the job in 2 business days. Satisfaction is
>>> guaranteed!
>>>
>>> snip ...
>>
>>
>>Have we been invaded? :-|
>
>Sure have, I sent a nasty note to owl@. I also did a whois and found the
>contact person for the domain so I also sent the note to john@.............
>Feel free to write your own note to the email spammers letting them know
>what you think of them. Make sure and send the message directly to them and
>not the list. I also contacted there ISP at postmaster@....... letting them
>know one of there accounts is spamming email. Later tonight I will call the
>number at the bottom of the message and leave a nasty voice mail message.
>
>I will also make a change to my mail server so email from olwsnest.com will
>not go out.
>
>Regards,
>Larry Cochrane
>Redwood City, PSN
>
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
*************************************************
Lucas Haag
HCR 66 Box 25A
Bartley, Nebraska 69020-9717
lhaag@..............
http://www.swnebr.net/~lhaag
"Through da keyboard, into the chips, over the copper,
through the fiber, back through the copper into the chips,
to the screen... NOTHING BUT NET!"
*************************************************
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ct@....... (Charlie & Terri Thompson -- @MicroRanch )
Subject: Jalisco Event
Date: Thu, 10 Apr 1997 19:40:45 -0500
My uploaded Jalisco event has a date error...the date should
be 4/8/97 NOT 4/9/97....daylight savings time caused me to
foul up the date on my computer...the date has been corrected
for all subsequent uploads to PSN.
Additionally, the USGS was LATE is posting this event and many
people could not find it...here's the USGS data:
97/04/08 15:23:43 18.55N 106.38W 33.0 4.9Ms B OFF COAST OF JALISCO, MEXICO
....better late than never!
-Charlie Thompson
Buda, Texas
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: for something totally different
Date: Fri, 11 Apr 1997 20:20:17 +1200
hi all,
for those of you in the northern states, canada, alaska ie
above 45 deg Nth keep an eye on the sky for some good auroral activity.
A major to severe geomagnetic storm started 7 hrs ago and is still in
progress.
dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Ground tilt and acceleration
Date: 11 Apr 97 12:56:30 EDT
Hi gang,
Harris and Cranswick recently discussed the response of a horizontal
long-period seismometer to horizontal acceleration and tilt. Aki & Richards,
"Quantitative Seismology", vol 1, 1980, p 485 sez " For almost all designs of
pendulum seismometers, it is not possible to distinguish between a horizontal
acceleration of the ground and a contribution from gravity due to tilt."
"...most seismologists have been content with the rather arbitrary assumption
that either acceleration or tilt dominates a particular signal." A mathematical
analysis (which is over my head) follows.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Ground tilt and acceleration
Date: Fri, 11 Apr 1997 12:06:18 -0600
While Paul Richards and Keiti Aki were writing Aki&Richards, Paul gave a
seminar on seismic instrumentation, partly as preparation for writing
the book. I was a graduate student and took the seminar and had to
present the paper about cross-coupling of tilt and inertial response,
the subject George Harris raised. The mathematics were over my head as
well, but I suddenly realized how a long-period "swinging gate"
seismometer would respond to the dynamic variations of tilt produced by
the passage of surface waves. During my presentation, I demonstrated
this truth with considerable literal "arm waving", rather than writing
equations on the board, and Paul, the consummate mathematician, told me
that he had not understood that implication from the equations. My
failure as a mathematician has always kept me relatively close to the
Earth.
Robert L Barns wrote:
>
> Hi gang,
> Harris and Cranswick recently discussed the response of a horizontal
> long-period seismometer to horizontal acceleration and tilt. Aki & Richards,
> "Quantitative Seismology", vol 1, 1980, p 485 sez " For almost all designs of
> pendulum seismometers, it is not possible to distinguish between a horizontal
> acceleration of the ground and a contribution from gravity due to tilt."
> "...most seismologists have been content with the rather arbitrary assumption
> that either acceleration or tilt dominates a particular signal." A mathematical
> analysis (which is over my head) follows.
> Bob Barns
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: Ground tilt and acceleration
Date: Fri, 11 Apr 1997 13:24:31 -0800
Ed C. is "close to the earth."
Is that like "down and dirty?"
:-) JCLahr
PS. Thanks for the insight into tilt vs horizontal motion.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Arrival Time Calculator
Date: Mon, 14 Apr 1997 10:55:58 -0800
I modified the arrival time calculator
(http://www.giseis.alaska.edu/Input/lahr/artim.html)
this weekend so that you can store your station coordinates on
your disk for repeated use with the web page. This is
done through the use of "cookies." This works with the
Netscape browser, but I'm not sure about others. If the
cookies don't work for you, coordinates can be still be
entered each time as usual.
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Smaller Lehmans?
Date: 14 Apr 97 15:23:34 EDT
Hi gang,
My Lehman has a boom about 30" long and it works fine. However, we have been
in the 'age of miniaturization' for a long time and I am curious to hear of any
experiences on the performance of smaller Lehmans. (Who has operated the
worlds' smallest with a period of at least 16"?). I am aware that Cochrane
finds that a Shackelford-Gunderson (which is much smaller) is a better
instrument but I would still like to know about small Lehmans. I'm also aware
that professional seismometers (e.g. Geotechs) have booms about a foot long.
I can't see why a smaller Lehman (say with a 15" boom) should be inferior
except that friction in the boom pivot would be more important. If this proves
to be a problem, there seems to be a neat fix--the 'Zollner suspension (1869!)'.
This is described in Aki & Richards, "Quantitative Seismology", 1980, vol 1, p
484. I built a very crude working model of this (with a 12" boom, 0.2kg mass
and a period of 14 secs.) and it looks very practical. In fact, I may modify my
Lehman to this design. Can anyone report experience with this suspension?
To save you the trouble of looking up Aki & Richards (although this should be
required reading for all of us), I'll take a stab at describing the Zollner--
Imagine a standard Lehman horizontal boom with the mass on the right end. The
main suspension wire comes down from the upper support and attaches to the boom
just to the left of the mass as per usual in a Lehman. Instead of a pivot on
the left end of the boom, a wire (which can be very thin because it carries
little load) is attached to the left end of the boom and this end of the boom
extends an inch or two to the left of the lower 'support'. The lower 'support'
is almost directly below the upper support. The wire on the left end of the
boom is attached to the lower support and makes an angle of ~45 deg. to the
boom. As usual, the period is determined by the angle from the vertical of the
line connecting the upper and lower 'support'.
Well, there's a whole bunch of questions for the group to munch on.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ct@....... (Charlie Thompson)
Subject: Re: Arrival Time Calculator
Date: Mon, 14 Apr 1997 16:29:11 -0500
Sounds like a nifty and useful addition...I'll give it a try.
thanks,
Charlie
>I modified the arrival time calculator
>
>(http://www.giseis.alaska.edu/Input/lahr/artim.html)
>
>this weekend so that you can store your station coordinates on
>your disk for repeated use with the web page. This is
>done through the use of "cookies." This works with the
>Netscape browser, but I'm not sure about others. If the
>cookies don't work for you, coordinates can be still be
>entered each time as usual.
>
>JCLahr
>################################## John C. Lahr
>################################# Seismologist
>################################ U.S. Geological Survey
>############################### c/o Geophysical Institute
>############################## 903 Koyukuk Drive
>~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
>###########################################################
> P.O. Box 757320 ################################
> Fairbanks, AK 99775 #################################
> Phone: (907) 474-7997 ##################################
> Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
> lahr@........ ####################################
> http://www.aeic.alaska.edu/Input/lahr/
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ct@....... (Charlie Thompson)
Subject: Re: Smaller Lehmans?
Date: Mon, 14 Apr 1997 16:39:12 -0500
Speaking of smaller Lehmans...I have a "mini-Lehman" that I designed
to fit under a 10-gallion aquarium..available for about $10 at Petsmart.
The glass allows you to show off your sensor as well. I have the
thing levelled up in my garage and it's been stable for about 1 month
now. Period is about 6 seconds. I don't have it wired up yet but
plan to do so soon. Aquarium dimensions are about 15w"x12h"x8d"
It will take up MUCH LESS room than my full-sized Lehaman w/box.
So much less that I can place two of the smaller mini-Lehmans in
the foot print of the single larger Lehman.
FFT's show that P and S waves have frequencies above 6 seconds so I
feel that the P and S waves will not be degraded by the use of a higher
natural frequency. Since L waves "tilt" the unit I believe that it may
prove sensitive enough for L waves regardless of period.
I'd like to hear everyone's thoughts on this ....maybe P and S are different
at different locations but my Texas data shows the P and S are almost
always higher than 6 seconds in frequency. This is how I distinguish
small quakes from 6-second background noise.
Regards,
Charlie Thompson
Buda, Texas
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jeff Batten <batten@...............>
Subject: Smaller Lehmans
Date: Mon, 14 Apr 1997 16:50:26 -0700
Speaking of smaller Lehmans...I have a "mini-Lehman" that I designed
to fit under a 10-gallion aquarium..available for about $10 at Petsmart.
The glass allows you to show off your sensor as well. I have the
thing levelled up in my garage and it's been stable for about 1 month
now. Period is about 6 seconds. I don't have it wired up yet but
plan to do so soon. Aquarium dimensions are about 15w"x12h"x8d"
It will take up MUCH LESS room than my full-sized Lehaman w/box.
So much less that I can place two of the smaller mini-Lehmans in
the foot print of the single larger Lehman.
FFT's show that P and S waves have frequencies above 6 seconds so I
feel that the P and S waves will not be degraded by the use of a higher
natural frequency. Since L waves "tilt" the unit I believe that it may
prove sensitive enough for L waves regardless of period.
What you can do is crank up the gain, and add a 20 sec low pass filter, you
will have no problem recording 20 second surface waves. Have different
stages in the amplifier. One for low, and one for high frequencies, then sum
them. Totally filter out the 6 second garbage. There really is not a need
for a horizontal with a period longer than 6 seconds with todays
electronics. With a shaped response one can have the best of both worlds.
Recorded a nice mammoth lakes trace today on my AS1.
Jeff
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: SCEC
Date: Tue, 15 Apr 1997 08:19:36 -0700
Hi --
The finger server at the Southern California Earthquake Center
(quake@..................... hasn't reported any events since 4/12 at
17:36UTC. I've seen two ~M3 events local to Southern California since then.
Does anyone know the status of the finger server?
Thanks,
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: SCEC
Date: Tue, 15 Apr 1997 08:49:45 -0700
I called Nick Sheckley at Caltech. Although he was not in Debi said the system
appears to be working fine.
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
Karl Cunningham wrote:
>
> Hi --
>
> The finger server at the Southern California Earthquake Center
> (quake@..................... hasn't reported any events since 4/12 at
> 17:36UTC. I've seen two ~M3 events local to Southern California since then.
>
> Does anyone know the status of the finger server?
>
> Thanks,
>
> Karl Cunningham
> La Mesa, CA.
> karlc@.........
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Re: Jalisco Event
Date: Wed, 16 Apr 1997 16:11:58 -0700
Greetings --
My upload of this same event also has an error -- I incorrectly reported it
as the Fox Island event, rather than as from Jalisco, MX. The two events
were separated in time by only minutes, and with only the Fox Island event
on the USGS list around that time, I made an assumption...
I wonder if the proximity of these two events in time contributed to the
tardy listing of the Jalisco event?
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Joe Irvine <Joe Irvine>
Subject: new address
Date: Wed, 16 Apr 1997 15:20:49
Http://www.scec.gps.caltech.edu
Joe Irvine
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "George A. Harris" <harris@........>
Subject: Smaller Lehmans
Date: Wed, 16 Apr 1997 20:07:07 -0700 (PDT)
For some time I have been experimenting with a small Lehman with a
9 inch boom. The secret is to support it with very flexible pivots.
Mine is an "L" shape with the short end pointing down.
The support is by means of two pieces of thin plastic. A piece of
1/4 inch recording tape makes a good pair. The vertical part of the
boom is about 3 inches long. At the bottom, a piece of tape pulls
to the right toward the weight. At the upper part, and somewhat to the
right of
the vertical is another tape which pulls toward the upper left. The
proper angle of the upper tape is that which would make the two
pieces of tape meet at or above the center of gravity of the boom.
My boom anly weighs a few ounces, but can easily be adjusted to a
period of at least 8 seconds in air. It could be longer if it is
covered but the adjustment is very critical, and the unit seems to
become very temperature sensative.
It is imporant that the stationary ends of the tape pivots be
capable of being adjusted to be in a vertical line. Also, if the
beam is allowed to move too much (like more than a quarter inch)
it tends to become unstable due to the geometry.
My present conclusion is that the only really useful long period
small unit should be a feedback one. My present model has two
magnets at the end of the boom (1/2 dia by 1/4 thick magnets) which
are above the two sides of a two inch coil. An EO sensor is
amplified and fed back to the coil. It is very sensitive, but I am
trying for a two axis model now.
George Harris
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: [Fwd: Letter from Alan Hale]
Date: Thu, 17 Apr 1997 09:01:51 -0700
This letter was forwarded to me and
I am passing it on to other groups
that would benefit from its content.
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
From: Karl Cunningham <karlc@.........>
Subject: Force Balance Idea
Date: Thu, 17 Apr 1997 16:13:07 -0700
Hi All --
A while back I had another idea for a force-balance seismometer...
Fantasy mode on...
Imagine a superconducting coil sitting on a table, with the ends shorted
together. Then place a magnet above it ... the magnet should be levitated
by the current induced in the superconducting coil. If one could measure
the current in the coil (without introducing loss), it would be a measure
of vertical acceleration on the magnet (including a dc current equivalent
to 1g). Even if there was some loss in the current measurement system, it
probably would be good enough to measure dynamic acceleration on the magnet
but certainly not keep it levitated.
The force coil I used in my FB seismometer has pretty good coupling to its
magnet, and a dc resistance of about 7 ohms. Thinking for a moment that if
the equivalent circuit of the force coil is an ideal coil with a 7-ohm
resistor in series with it, I reasoned that if I connected a NEGATIVE 7-ohm
resistor in series with the positive 7-ohm resistor, the whole thing would
simulate a superconducting coil. Shorting the ends of the simulated
superconducting coil together would yield the situation in the above
paragraph.
Back to the real world...
There is such a thing as a "negative impedance convertor" (NIC), which is a
circuit composed of an op-amp and a handful of resistors. It provides a
terminal that has all the characteristics of a negative resistance with
respect to ground. By adjusting the values of the resistors, the value of
the negative resistance can be adjusted.
I built one of these circuits, adjusted it for about negative 7 ohms, and
connected it to my coil, which was set up on my Lehman mechanical system
(horizontal). To my astonishment, it worked. It resisted movement very
well (balancing the force), and the current in the coil was proportional to
the force (acceleration on the mass). As a test, I un-leveled the base of
the Lehman a bit and pulled the mass to the upper stop. When I let it go
without the NIC connected the mass fell to the other side in 1/2 second or
less. With the NIC connected, it took more than 20 MINUTES for the mass to
fall to the other stop!
Elecronically, this is a very simple system. It is a force-balance
accelerometer with only one coil, no separate position detector, and only a
very small number of components to do the feedback.
Now for the problem. (There's always a catch)
When it is just balancing the resistance of the force coil, the NIC becomes
unstable (oscillates). Adjusting it to just shy of that point stops the
oscillation, but the stability of that adjustment is poor. The coil is
copper (~0.3%/deg C resistance tempco), and not matched by the fixed
resistors I used. Also, near the critical adjustment, drift of the op-amp
is multiplied by something akin to the reciprocal of the match in
resistances -- it gets pretty bad.
Looking at noise, it was still far above the 6-second background noise. I
moved on to other ideas.
Anyway, I thought I'd throw it out to the group. Maybe some of you out
there have ideas that will overcome the problems.
Karl Cunningham
La Mesa, CA.
karlc@.........
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From: Greg Lyzenga <lyzenga@.................>
Subject: Force Balance article
Date: Fri, 18 Apr 1997 09:12:35 -0700
Hi folks:
Sorry to bother you with a rehash of something discussed earlier -- I
couldn't seem to find it in my archives of old messages.
Some months ago, somebody mentioned a journal article that had been
published describing the design and construction of a force balance
seismometer system. I think this might be a good project to turn loose
some of my students on. Could somebody please refresh my memory on the
citation I'm thinking of?
Thanks x 10^6 !
- Greg
|Gregory A. Lyzenga <lyzenga@.................> *** (909) 621-8378
|Dept. of Physics, Harvey Mudd College *** fax (909) 621-8887
|Claremont, CA 91711-5990
http://www.physics.hmc.edu/profs/lyzenga.html
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From: Ron Westfall <westfall@......>
Subject: Re: Force Balance article
Date: Fri, 18 Apr 1997 11:38:56 -0700
Greg Lyzenga wrote:
> Some months ago, somebody mentioned a journal article that had been
> published describing the design and construction of a force balance
> seismometer system. I think this might be a good project to turn
> loose some of my students on. Could somebody please refresh my
> memory on the citation I'm thinking of?
The reference you might be thinking of was:
A miniature wide band horizontal-component feedback seismometer.
Journal of Physics E: Scientific Instruments
1977
Ovulate 10
I found the article in our local university library. The design
(especially the controlling electronics) is not fully specified in
the article, but enough clues are provided that the details can
probably be worked out. The only other issue was that the mechanical
design called for some materials I had never heard of (Ni-Span I
think it was).
Good Luck
Ron Westfall
westfall@......
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Public Seismic Network Mailing List (PSN-L)
From: Jeff Batten <batten@...............>
Subject: FBS stuff
Date: Fri, 18 Apr 1997 13:42:36 -0700
If you are trying to build your own force balance seismometer you should
check out
A miniature wide band horizontal-component feedback seismometer.
Journal of Physics E: Scientific Instruments
1977
Ovulate 10
It has a pretty good description of a FBS.
I think that a lot of readers of this group have the skills to construct
the seismometer. The article has a good drawing and photos. If you have a
milling machine and lathe, give it a try.
Another good reference.
The design of miniature wide band seismometers
M. J. Usher and C Guralp
Geophysical Journal of the Royal Astronomical Society
1978 (55), 605-613
M J usher
I W Buckner
R F Burch
If you like seeing a lot of unique designs for seismometers check out old
Bull. Seismol. Soc. Am.
The BSSA has a few hundred articles on seismometer design back to 1906.
You will probably have to visit a university library to find the above
references.
Jeff Batten - Research Engineer
Caltech Seismo Lab
818-395-6965
Fax-818-564-0715
_____________________________________________________________________
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Jeff Batten - Research Engineer
Caltech Seismo Lab
1200 E. California Bl.
Pasadena, Ca.
91125
818-395-6965
Fax-818-564-0715
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Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Force Balance article
Date: Fri, 18 Apr 1997 18:02:36 -0700
Greg Lyzenga wrote:
>
> Hi folks:
> Sorry to bother you with a rehash of something discussed earlier -- I
> couldn't seem to find it in my archives of old messages.
>
> Some months ago, somebody mentioned a journal article that had been
> published describing the design and construction of a force balance
> seismometer system. I think this might be a good project to turn loose
> some of my students on. Could somebody please refresh my memory on the
> citation I'm thinking of?
>
> Thanks x 10^6 !
>
> - Greg
>
> |Gregory A. Lyzenga <lyzenga@.................> *** (909) 621-8378
> |Dept. of Physics, Harvey Mudd College *** fax (909) 621-8887
> |Claremont, CA 91711-5990
> http://www.physics.hmc.edu/profs/lyzenga.html
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
Hi
You might also try Sientific American Sept 1975 Amateur Scientist.
I think you could call it a force balance seismometer.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Force Balance article
Date: Sun, 20 Apr 1997 14:54:28 -0700
At 06:02 PM 4/18/97 -0700, Barry Lotz wrote:
>Hi
> You might also try Sientific American Sept 1975 Amateur Scientist.
>I think you could call it a force balance seismometer.
>
This is the Shackleford-Gundersen Seismometer article. It's not really a FB
sensor because the feedback to the coil is AC coupled. I think that it can
be turned into a FB sensor by adding a resistor where the DC block
capacitor goes. You need to add some capacitance across the resistor so the
sensor won't oscillate. I think this makes a lead circuit.
I played around with this a few months ago. By DC coupling the feedback
coil you now get a DC signal that changes with the tilt of the sensor. As
you increase the feedback you need to tilt the sensor more to get the same
output. This has the same effect as my two other FB sensors (the ADX05 and
the FBA-31). As you tilt the sensor, using the 1g force of mother earth,
you get a DC output that increases until the sensor is straight up and
down. I was unable to get my SG sensor to go that far because of the weight
of the pendulum and the amount of current I could supply to the coil.
I have the SA Sept 1975 article on my Website at
http://psn.quake.net/sgsendor.html.
Regards,
Larry Cochrane
Redwood City, PSN
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From: Robert L Barns <75612.2635@..............>
Subject: Re: Force Balance article
Date: 20 Apr 97 20:21:18 EDT
Greg,
I can't answer your question about the article reference but I have a few of
my own.
Somewhere I read that the Harvey Mudd Coll. uses a mercury tiltmeter as a
seismometer. If so: 1. Is this a commercial device? If so, who made it? 2.
Could you tell us about it--size, period, performance, stability, etc. etc.?
One of these is described in great detail in Sci. Am. mag., Nov. 1973 p124...
and sounds easy to make and capable of good performance. Is your sensor like
this one? I am also interested in your opinion of this article.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: ALERT MONSTER QUAKE !!!!!!
Date: Tue, 22 Apr 1997 00:32:11 +1200
HI ALL,
Just recorded a large event here in New Zealand still
waiting for a report on the NEIC page
No S-P but it is the largest amplitude lower freq. waves that I have
ever recorded
LP waves still coming in 20 minutes after the original arrival
original arrival 1212:10 UTC Mon 21 Apr 97
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: bzimmerman@............
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Mon, 21 Apr 1997 08:44:46 -0500 (EST)
Thanks for the warning Dave. I ran down to check and watched what look
like surface waves rolling in.
Brian S. Zimmerman
Department of Geosciences
Edinboro University of Pennsylvania
Edinboro, PA 16444
Phone: (814) 732-2207
Email: BZimmerman@............
On Tue, 22 Apr 1997, David A Nelson wrote:
> HI ALL,
> Just recorded a large event here in New Zealand still
> waiting for a report on the NEIC page
> No S-P but it is the largest amplitude lower freq. waves that I have
> ever recorded
>
> LP waves still coming in 20 minutes after the original arrival
>
> original arrival 1212:10 UTC Mon 21 Apr 97
>
>
>
> Dave
> Dave A. Nelson
>
> 24 Jensen St.,
> Green Is., Dunedin,
> South Is.. New Zealand.
>
> http://psn.quake.net/dave/home.htm ( world wide access )
> http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
>
> SOD'S LAW--
> When Something Does Go Wrong, There Is Sod All You Can Do About It
>
>
> When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
> Discovered That The Wrong Cover Has Been Removed
>
> When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
> Discovered That The gasket Has Been Left Out
>
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: bob@................. (Bob Hammond (USGS-AVO Geophysicist))
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Mon, 21 Apr 1997 04:51:14 -0800
I got the surface waves here too on my home seismograph. And got roused out of bed by a quake alarm for work.
The borehole broadband seismograph is going strong.
It's not in Alaska.
Bob Hammond
Fairbanks
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Tue, 22 Apr 1997 00:58:42 +1200
good one Brian,
still waiting for one of the data centres to show
some info
it is shown in Larry's event list on his page just downloaded his
..LC1 file but it is not shown too well will try some of his other sensor
files I will put my one up there soon.
dave
At 08:44 AM 4/21/97 -0500, you wrote:
>
>Thanks for the warning Dave. I ran down to check and watched what look
>like surface waves rolling in.
>
>Brian S. Zimmerman
>Department of Geosciences
>Edinboro University of Pennsylvania
>Edinboro, PA 16444
>
>Phone: (814) 732-2207
>Email: BZimmerman@............
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Tue, 22 Apr 1997 01:04:22 +1200
ok Bob No, by the amplitude that it has on my short period sensors it
has to be in the sth Pacific either to the south of me in the Macquarie
Ridge area or to the north inthe Fiji - Tonga area and I am picking M8 +
dave
At 04:51 AM 4/21/97 -0800, you wrote:
>I got the surface waves here too on my home seismograph. And got roused
out of bed by a quake alarm for work.
>The borehole broadband seismograph is going strong.
>
>It's not in Alaska.
>
>Bob Hammond
>Fairbanks
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Mon, 21 Apr 1997 05:08:36 -0700
Hi,
The event was around 9200 to 9500km from me. My SG sensors is giving me a
Ms7.9 to Ms8.0! I don't know if it's really that large, will see when USGS
reports something.
Regards,
Larry Cochrane
Redwood City, PSN
At 12:32 AM 4/22/97 +1200, you wrote:
>HI ALL,
> Just recorded a large event here in New Zealand still
>waiting for a report on the NEIC page
> No S-P but it is the largest amplitude lower freq. waves that I have
>ever recorded
>
> LP waves still coming in 20 minutes after the original arrival
>
> original arrival 1212:10 UTC Mon 21 Apr 97
>
>
>
> Dave
> Dave A. Nelson
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: bob@................. (Bob Hammond (USGS-AVO Geophysicist))
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Mon, 21 Apr 1997 05:16:59 -0800
preliminary location is 7.6S, 166.3E, 7.5mw
Bob Hammond
Fairbanks
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Tue, 22 Apr 1997 01:19:21 +1200
gidday Larry,
just looked at your uploaded event looks impressive
Dave Now 01:18 Local
At 05:08 AM 4/21/97 -0700, you wrote:
>Hi,
>
>The event was around 9200 to 9500km from me. My SG sensors is giving me a
>Ms7.9 to Ms8.0! I don't know if it's really that large, will see when USGS
>reports something.
>
>Regards,
>Larry Cochrane
>Redwood City, PSN
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Mon, 21 Apr 1997 05:32:04 -0700
David A Nelson wrote:
>
> HI ALL,
> Just recorded a large event here in New Zealand still
> waiting for a report on the NEIC page
> No S-P but it is the largest amplitude lower freq. waves that I have
> ever recorded
>
> LP waves still coming in 20 minutes after the original arrival
>
> original arrival 1212:10 UTC Mon 21 Apr 97
>
>
>
> Dave
> Dave A. Nelson
>
Hi all-
I got it all here also.
Barry
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From: Dennis Leatart <ASTROSEEK@.........>
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Mon, 21 Apr 1997 07:13:32 -0700
Hi Everyone!!
I picked it up also--woke me up (my alarm that is!!). I am still
picking up what looks like Rayleigh waves one hour after the event!!!
--
_____ __
| \.-----.-----.-----.|__|.-----.
| -- | -__| | || ||__ --|
|_____/|_____|__|__|__|__||__||_____|
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ct@....... (Charlie & Terri Thompson -- @MicroRanch )
Subject: Murphy's Law and Monster Quakes
Date: Mon, 21 Apr 1997 09:12:30 -0500
Last night I powered everything down due to a violent electrical storm.
This morning I powered up the machine in the middle of giant L-waves!
If I had gotten out of bed 10 minutes earlier I would have bagged the
complete event!
I don't know where the quake is but it must have been the Mag 7+
that we record about once a month.
Murphy's Law...
-Charlie
_ ________________________________________________ _
/ ) | | ( \
/ / | Charlie Thompson WB4HVD | \ \
_( (_ | _ e-mail: ct@....... _ | _) )_
(((\ \> |/ ) http://www.onr.com/user/ct/ct.html ( \| </ /)))
(\\\\ \_/ / Latitude 30.112 N \ \_/ ////)
\ / Longitude 97.891 W \ /
\ _/ Seismic Station .BUE \_ /
/ / |________________________________________________| \ \
/ / \ \
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From: David A Nelson <dann@........>
Subject: NEIC report
Date: Tue, 22 Apr 1997 02:17:27 +1200
97/04/21 12:02:25 12.47S 166.21E 33.0 7.9Ms B SANTA CRUZ ISLANDS
origin 12:02:25 arrival here 12:09:07 travel time ~ 7
minutes 18 sec
the second arrival on my 15 min. file at ~ 12:18 could be this event
97/04/21 12:11:28 13.11S 166.24E 33.0 6.1Mb C VANUATU ISLANDS
Dave
Keen to see the Mw for this one I have recorded Ms 7.7-7.9 up here
before but NEVER with this sort of amplitude
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Dennis Leatart <ASTROSEEK@.........>
Subject: Monster Quake!!!
Date: Mon, 21 Apr 1997 07:26:31 -0700
Hi!!
The quake was located in the Santa Cruz Islands--Northeast of Australia
and appears to have taken place in the ocean. Tidal wave alert???
Dave-- you are closests to this event -- did you feel it??
12.47S and 166.21E--- Mag.7.9 ee-gad!!!
--
_____ __
| \.-----.-----.-----.|__|.-----.
| -- | -__| | || ||__ --|
|_____/|_____|__|__|__|__||__||_____|
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Murphy's Law and Monster Quakes
Date: Tue, 22 Apr 1997 02:29:07 +1200
check my last psn posting Charlie there is the NEIC report within.
dave
At 09:12 AM 4/21/97 -0500, you wrote:
>Last night I powered everything down due to a violent electrical storm.
>
>This morning I powered up the machine in the middle of giant L-waves!
>If I had gotten out of bed 10 minutes earlier I would have bagged the
>complete event!
>
>I don't know where the quake is but it must have been the Mag 7+
>that we record about once a month.
>
>Murphy's Law...
>
>-Charlie
> _ ________________________________________________ _
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Monster Quake!!!
Date: Tue, 22 Apr 1997 02:37:08 +1200
Dennis,
It was ~ 6-7000 Km to the NNW of me to be felt a M8 would have to be
within 1000km like the
M8.2 near Macquarie Is. ~900 km SW of me in the late 1980's 1988 I think
Dave
At 07:26 AM 4/21/97 -0700, you wrote:
>Hi!!
>
>The quake was located in the Santa Cruz Islands--Northeast of Australia
>and appears to have taken place in the ocean. Tidal wave alert???
>Dave-- you are closests to this event -- did you feel it??
>
>12.47S and 166.21E--- Mag.7.9 ee-gad!!!
>--
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Mon, 21 Apr 1997 11:49:47 -0600
Coming in to find this great flurry of PSN email after Dave Nelson's
post, I figured I would try a find out something upstairs at NEIC. The
only things that Waverly Person told me that you may not know is that
there have been no reports of a tsunami and no reports damage of damage
as yet.
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: ALERT MONSTER QUAKE !!!!!!
Date: Mon, 21 Apr 1997 12:12:13 -0600
Larry's .LC3 made a very nice record, both in velocity and integrated to
displacement, that makes me interested in teleseismic long-period
seismology again.
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: [Fwd: Tsunami Bulletin (fwd)] Re: ALERT MONSTER QUAKE !!!!!!
Date: Mon, 21 Apr 1997 13:30:16 -0600
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
Gee, for a minute when I saw the name "Santa Cruz Island" I thought we
were going to get our California tsunami, but the lat/long put this in the
southwest Pacific... oh well... a later report cancelled the tsunami
alert, already.
Gotta go teach class, talk to you later.... JB
---------- Forwarded message ----------
Date: Mon, 21 Apr 1997 12:57:59 GMT
From: Alaska Tsunami Warning Center <atwc@..........>
To: TSUNAMI@.............
Subject: Tsunami Bulletin
TSUNAMI BULLETIN NUMBER 1
ALASKA TSUNAMI WARNING CENTER/NOAA/NWS
ISSUED APR 21 AT 1253 UTC
....THIS IS A TSUNAMI ADVISORY BULLETIN FOR ALASKA, BRITISH
COLUMBIA, WASHINGTON, OREGON, AND CALIFORNIA ONLY...
NO, REPEAT NO, WATCH OR WARNING IS IN EFFECT.
AN EARTHQUAKE, PRELIMINARY MAGNITUDE 7.7, OCCURRED AT
0402 ADT ON APR 21, OR 0502 PDT ON APR 21, OR 1202 UTC ON APR 21.
THE EARTHQUAKE WAS LOCATED IN THE GENERAL AREA OF:
SANTA CRUZ IS. NEAR 12.2S, 166.3E.
THE PACIFIC TSUNAMI WARNING CENTER AT EWA BEACH, HAWAII WILL
ISSUE BULLETINS FOR OTHER AREAS OF THE PACIFIC.
EVALUATION: BASED ON THE LOCATION, MAGNITUDE AND HISTORICAL
RECORDS, THE EARTHQUAKE WAS NOT SUFFICIENT TO GENERATE A TSUNAMI
DAMAGING TO CALIFORNIA, OREGON, WASHINGTON, BRITISH COLUMBIA OR
ALASKA. SOME AREAS MAY EXPERIENCE SMALL SEA LEVEL CHANGES.
A FEW SELECTED ETA'S FOLLOW FOR INFORMATION AND REFERENCE:
LA JOLLA, CA 1744 PDT APR 21 TOFINO, BC 1812 PDT APR 21
SAN FRANCISCO,CA 1748 PDT APR 21 SITKA, AK 1655 ADT APR 21
CRESCENT CITY,CA 1730 PDT APR 21 KODIAK, AK 1628 ADT APR 21
NEAH BAY, WA 1816 PDT APR 21 SHEMYA, AK 1357 ADT APR 21
BULLETINS WILL BE ISSUED HOURLY TO KEEP YOU INFORMED OF THE
PROGRESS OF THIS EVENT UNTIL THE PACIFIC TSUNAMI WARNING
CENTER ISSUES A CANCELLATION OR FINAL BULLETIN.
From: Karl Cunningham <karlc@.........>
Subject: Unknown Quake
Date: Mon, 21 Apr 1997 22:15:08 -0700
Hi Folks --
Did anyone get an earthquake at about 00:44:50 UTC 4/22? I saw a ~M3.9
about 350KM from here (San Diego, CA area), likely in Mexico. I don't see
it on any of the lists yet.
Thanks.
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Trinidad Mw6.5
Date: Tue, 22 Apr 1997 23:41:09 +1200
Charlie,
hope you had the recorder going for the Trinidad event
looking forward to seeing a winquake posted from you.
Dave N
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Tony Carrasco <tcarrasc@................>
Subject: Re: Unknown Quake
Date: Tue, 22 Apr 1997 09:03:17 -0700 (PDT)
Karl,
We also received a quake around that time. I'm not sure of the epicenter or
magnitude, but it was stronger on our Barrett Dam Station then our Vista
and Palomar Stations. I also noticed a similar quake this morning, perhaps
a small aftershock.
TONY
SDSU
>Hi Folks --
>
>Did anyone get an earthquake at about 00:44:50 UTC 4/22? I saw a ~M3.9
>about 350KM from here (San Diego, CA area), likely in Mexico. I don't see
>it on any of the lists yet.
>
>Thanks.
>
>
>Karl Cunningham
>La Mesa, CA.
>karlc@.........
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
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From: roger baker <rcbaker@........>
Subject: micromanometers, etc
Date: Tue, 22 Apr 1997 12:12:23 -0500 (CDT)
Friends,
I just stumbled onto your group by accident while surfing the
topic of microbarometers. It turns out I know Jack Herron well since I
write a Science Hacker column for the Society for Amateur Scientists
Bulletin which he edits. But anyhow, I thought I would pass along a nice
little design for a sensitive-as-all-get-out little micromanometer. My
specialty is cheap home brew instrumentation. Incidently, I also have a
homebrew design for a sensitive vertical seismometer that you can build
for $20 or so and which is sensitive enough so that it is constantly
recording background noise here in Austin, Texas and has a period of ten
seconds or so (dont really remember exactly). It was really designed as a
tidal gravimeter and all tidal gravimeters are also thermometers. Without
temperature buffering, it was never stable enough to see daily gravity
fluctuations, but a bad gravimeter can easily be a good seismometer if
the temperature variations are long compared to the seismic disturbances
being monitored, as is generally the case. If I got some of the addresses
wrong and you think others might be interested in this stuff, could
someone be so kind as to repost?
--Yours, Roger Baker (Science Hacker)
1303 bentwood, Austin, Texas
A Supersensitive Micromanometer and the Uses Thereof
There are many reasons that one might want to accurately measure the
volume of a gas. Of course one might choose to buy a silicon
diaphragm pressure sensor, but these have the disadvantage of being less
sensitive, more expensive and not nearly as fun to build.
Here is a relatively cheap easy way to build a simple pressure guage for
between $10 and $20 that is sensitive to nanoliter changes in volume in a
gas or liquid, and which therefore allows one to build many sort of
scientific instruments. Some examples might be a tiltmeter, a carbon
dioxide measuring device, a microbarovariometer (essentially a detector
for subsonic air pressure waves that can be used to detect nuclear
explosions as well as nearby weather disturbances). Other uses for such a
device might be an infrared thermometer, a flowmeter, a micropipette
calibrator, a tactile pressure sensor for a robot hand, as well as many
other kinds of instruments. Due to the easy compressibility of gases,
measuring either very slight pressure changes in the volume or the
pressure of a gas near atmospheric pressure amount to much the same thing.
Experience building such a sensor develops easily transferrable
knowledge useful for building many other types of sensitive instruments
and detectors requiring optical detection and electronic amplification.
A scrap of glass tubing, a little silicone rubber, a little glycerine and
blue food coloring and a few scraps of aluminum and a nut and bolt
comprise the sensor. The associated electronics can be nothing much more
than a 324 op amp and battery power supply.
In principle my instrument is very easy to understand. One simply creates
a short column perhaps one millimeter in diameter of food coloring and
glycerine in
a constriction in a small glass tube. Then one measures the variation in
light absorption caused by a slight movement of the column. The column
responds to any very slight change in external gas pressure, causing it
to intercept to a variable degree an optical light beam transversing the
tube. This is my own version of the old fashioned manometer that in its
classic version used the motion of a column of mercury or other liquid
trapped in the low curved portion of a U-tube to measure relative
pressure changes between the two vertical arms.
However, my version uses a short section of a horizontal tube and has
various advantages. For one thing, it is very small and cheap to set up
and the use of solid state optics makes it very sensitive. The basic
principle of the gadget is that the short column of liquid tends to
center itself in the narrowest part of the glass tube due to surface
tension. If too much air pressure forces the column over to one side of
the constricted tube, the column merely becomes unstable, breaks (since
pure glycerine does not form stable bubbles), and the surface tension of
the liquid regenerates the column near the center of the tube. One can
zero the column in relation to the optical detectors by tilting the glass
tube very slightly so that one edge of the nearly horizontal fluid column
shifts position slightly due to the combination of the forces of surface
tension and gravity until it is properly positioned to partially
intersect the light beam.
I use two super-bright red LEDs from Radio Shack for less than $2 apiece
as both the detector and the emitter. These LEDs make wonderful emitter
and detector combinations since the red light is very bright and
adjustments are easily made by sight. The second LED being used as a
detector is operated in the zero bias voltage mode. In other words, it is
allowed to function like a tiny solar battery short-circuited with an
external resistor. A one meg resistor loads it enough to make its output
linear without reducing the output voltage too much. Under these
conditions, the second LED becomes a very linear red light detector in
its voltage output, which can be easily measured with any of a number of
high impedence voltmeter or op amp circuits.
Each LED has its focusing lens ground off flat and is then glued behind a
small hole in a small aluminum plate. The two plates are bolted together
so they grip the constriction in the glass tube from opposite sides.
Silicone rubber is used to make little depressed pads on the aluminum
plates that cradle the tube in the proper adjustable position so that the
light beam from the LEDs just intersects the edge of the blue column of
glycerine. The output voltage of such a sensor can easily be made to have
a range of 100 to one with movement of the column. This output is probably
responsive to a few nanoliters of volumetric change at near atmospheric
pressure.
A voltage controlled oscillator from a one dollar 4066 CMOS phase locked
loop chip and small piezo speaker are useful to give the experimenter an
audible indication of small changes during the initial setup and
experimentation stages. The day I first built such a device, I found it
interesting to use such a setup to audibly monitor the frequent
barometric pressure swings associated with a passing storm front. I
believe such a device could probably be modified to total the number and
intensity of changes in atmospheric pressure to warn of nearby weather
disturbances
In this latter application of my sensor, I used a very slow air leak in
parallel with my
micromanometer and attached them both to a large reservoir of air in the
form of a one gallon glass jug. In this way the instrument responds to
rapid atmospheric pressure changes acting on the air in the jug. Roughly
speaking, the device might respond to pressure changes ranging from
perhaps one second to 10 minutes, whereas very gradual changes in
absolute barometric pressure are automatically eliminated by the slow
bypass air leak.
Not having a two hole stopper handy, I drilled two holes in a small
aluminum plate and sealed this plate directly to the mouth of the jug
with silicone. Then I sealed two short lengths of vinyl aquarium tubing
in the plate with more silicone. One of the tubes is attached to the
micromanometer, which is clamped in an adjustable position nearby, and
the other tube has a little piece of cotton or paper in the end. It is
then clamped shut with a bulldog paper clip so that the cotton or paper
prevents it from closing completely and generates the slow leak that
allows the manometer to follow very slow changes in atmospheric pressure
while retaining high sensitivity to rapid fluctuations,
Once the mechanical elements are working properly, a chart recorder or
computer data link can be used for quantitiative work. For about $125,
one can get a nice LCD digital multimeter from Radio Shack that includes
software and a serial port connector to turn almost any PC into a chart
recorder. (thanks for this latter tip from someone in the quake
discussion group; I just ran out and got one yesterday)
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Santa Cruz boomer
Date: 22 Apr 97 14:02:47 EDT
Re:4/21 12:2:25 Santa Cruz Is.!!!
A winner! I turned on the monitor yesterday morning and it had been coming in
for about 15 mins so I saw most of it in real time. It was a rather quiet day
here and it was above background for more than 4 hrs.
No P or S identifiable--from here it is 120 deg (8320 mi) so just out of range
of the tables. The surface waves arrived about 48 mins after the P (calc.).
The surface waves had a max. p-p velocity of 168,000 nm/sec or almost 0.2mm/sec.
The FFT of these peaked rather sharply at 0.04Hz. The sig/noise ratio was about
240.
The coda seems to me to be remarkably complex--I'll be interested to download
some other 'grams to see how they compare. I'll send my record (970412B.RLB) to
the archives soon.
Bob Barns in far away Berk. Hts., NJ
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jeff Batten <batten@...............>
Subject: Re: Unknown Quake
Date: Tue, 22 Apr 1997 11:27:52 -0700
At 09:03 AM 4/22/97 -0700, you wrote:
>Karl,
>
>We also received a quake around that time. I'm not sure of the epicenter or
>magnitude, but it was stronger on our Barrett Dam Station then our Vista
>and Palomar Stations. I also noticed a similar quake this morning, perhaps
>a small aftershock.
>
I installed that Palomar Station two weeks ago. Nice to see that puppy
works. It is a STS-2 with a Quanterra Data Logger, Frame relay data
transmission, GPS Clock.
A typical Trinet Station.
Located just across from the 18" schmidt of Shoemaker-Levy fame. What was
nice about installing the Palamar station was getting a one hour tour of the
200" scope.
Jeff Batten - Research Engineer
Caltech Seismo Lab
1200 E. California Bl.
Pasadena, Ca.
91125
818-395-6965
Fax-818-564-0715
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: roger baker <rcbaker@........>
Subject: Re: micromanometers, etc
Date: Tue, 22 Apr 1997 13:50:36 -0500 (CDT)
To Dennis and other interested parties:
In essence, my seismometer/gravimeter is a horizontal glass
filament with a tiny lens and a little chunk of iron mounted near the
free end, and carefully mounted in a little glass case.
A magnet is adjustably mounted nearby so that it very nearly balances the
weight of the free end and relatively heavy of the filament, greatly
magnifying
the force of gravity. The lens is actually the tip of the filament fused
into a glass bead. This free end swings up and down past a light emitter
and detector behind little slits in aluminum foil. Therefore only a few
microns of vertical motion are easily registered with a circuit similar
to that used with my micromanometer. Of course, one can also use a
phototransistor as a detector for the narrowest light beams and best
sensitivity. The glass bead acts as an optical element to make the light
emerging from one slit converge back into the other slit; the two
straddling the swinging filament with its bead lens.
The Society for Amateur Scientists does have a web page but
unfortunately, it doesn't get updated very often. Check with Jack Herron,
who is probably also on this list. Sorry I don't have a web page yet.
--Yours, Roger Baker
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: micromanometers, etc
Date: Tue, 22 Apr 1997 12:35:51 -0800
Roger,
Welcome to the PSN! I hope you will join in the
discussion.
I'm having some difficulty visualizing the glass tube
used for the pressure sensor. What is the inside
diameter, away from the 1 mm diameter constriction?
How wide is the constricted area? A diagram would
help a lot! I guess that the diameter tapers down
to 1 mm and then back again. Does the rate of taper
matter much? The fluid is only located
in the tapered region, and centers itself at the
narrowest point. Then the led's sense the position of
one of the two ends of the fluid.
Sounds like a fun experiment. Is this on the Amateur
Scientist web site?
Thanks,
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: roger baker <rcbaker@........>
Subject: Re: micromanometers, etc
Date: Tue, 22 Apr 1997 19:09:30 -0500 (CDT)
Dear Dr. Lahr,
The tube was 4mm pyrex heated in a propane torch and
pulled out from an initial 3 inches to 3 1/2 inches when soft to give a
constricted central portion that tapers to an internal bore of about 1
mm. Nothing is very critical, but you might have to tinker around a bit.
One thing I did not mention is that you may have to mask the light source
and detector with black masking tape to exclude light that could
circumvent the liquid column.
You can run the LED in series with about 200 ohms and at 12 volts, which
is also used to power the 324 op amp.The midpoint between two similar resistors
used with a voltage follower config that ties to one leg of the detector
(LED and 1 meg in parallel). The other terminal of the detector is tied
to a second voltage follower. Since this only uses two of the op amps on
the chip, you have two left over to amplify the signal or filter it. Even
the unamplified output signal might be 100 millivolts due to the brightness
of the LED so excessive signal noise should not be a problem compared to
temperature drift. the sensor should be mounted on some type of swivel
mount so it can be tilted to fine tune the column after rough adjustments
have been made via the aluminum plates. More than this I cannot say,
having just built the first version only a few days ago. Actually this
micromanometer was designed for another purpose entirely: to make rapid
accurate measurements in the field of the carbon dioxide content of air.
The principle here is to trap air in two identical flat chambers, one of
which has a CO2 absorbant in its wall. Obviously one chamber will start
to develop a slight vacuum as the CO2 disappears from that chamber, all
other factors like temperature being equal. The challenge is to devise a
simple manometer that will respond to one part per four thousand change in
the volume of two small chambers of air of capacity circa 1 cc each. This
is response to comments below). --Roger
On Tu, 22 Apr 1997, Dr. John Lahr (USGS-GI Seismologist) wrote:
>
> Roger,
>
> Welcome to the PSN! I hope you will join in the
> discussion.
>
> I'm having some difficulty visualizing the glass tube
> used for the pressure sensor. What is the inside
> diameter, away from the 1 mm diameter constriction?
> How wide is the constricted area? A diagram would
> help a lot! I guess that the diameter tapers down
> to 1 mm and then back again. Does the rate of taper
> matter much? The fluid is only located
> in the tapered region, and centers itself at the
> narrowest point. Then the led's sense the position of
> one of the two ends of the fluid.
>
> Sounds like a fun experiment. Is this on the Amateur
> Scientist web site?
>
> Thanks,
> JCLahr
> ################################## John C. Lahr
> ################################# Seismologist
> ################################ U.S. Geological Survey
> ############################### c/o Geophysical Institute
> ############################## 903 Koyukuk Drive
> ~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
> ###########################################################
> P.O. Box 757320 ################################
> Fairbanks, AK 99775 #################################
> Phone: (907) 474-7997 ##################################
> Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
> lahr@........ ####################################
> http://www.aeic.alaska.edu/Input/lahr/
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: micromanometers, etc
Date: Tue, 22 Apr 1997 17:58:44 -0800
Roger,
Thanks for the further details. Don't know how soon I'll be
able to play around with this, but it sounds interesting. Let
me know if you get your CO2 detector working. Seems like
a clever plan to me. Is there a substance that will absorb
CO2 but not other gases? Would it also absorb CO?
JCLahr
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: FYI: Santa Cruz Islands Quake Update
Date: Wed, 23 Apr 1997 11:35:29 -0700
FYI
Discovered some new information regarding damage and tsunamis from the
recent Santa Cruz Ms 7.9 earthquake and posted it in a Seismo-Watch
E-mail Alert Bulletin you can see here:
http://www.seismo-watch.com/EQS/AB/9704/970423-101.SC6.1.html
The archive for past Alert Bulletins is here:
http://www.seismo-watch.com/EQS/AB/ABA.html
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Dennis Leatart <ASTROSEEK@.........>
Subject: Mariana's Event (6.3)
Date: Wed, 23 Apr 1997 15:30:49 -0700
Hello everyone!!!
Did anyone else pick up the Mariana's Event --Mag. 6.3- today 4/23/97?
I have what appears to be two events separated by about 8 minutes
apart?? Thanks!!!
--
_____ __
| \.-----.-----.-----.|__|.-----.
| -- | -__| | || ||__ --|
|_____/|_____|__|__|__|__||__||_____|
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Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Santa Cruz Is. events map
Date: Thu, 24 Apr 1997 19:25:03 +1200
hi ya all,
for those interested, at the top of my quakes page, I have
added for a short period of time a regional map showing the Ms 7.9 and
aftershocks
cheers Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: roger baker <rcbaker@........>
Subject: Seismometer design
Date: Thu, 24 Apr 1997 11:11:45 -0500 (CDT)
Zero Motion Feedback Principle for Seismometers?
While pondering seismometer design over the last couple of days, it
occurs to me that there might be great instrumental advantages to
introducing a mass position resoration feedback loop into the design.
This would give the result that the moving mass usually associated with
seismometers is kept stationary by imposing a force, especially an
opposing magnetic force, generated with a sensitive motion detector and
an amplified feedback loop.
I initially thought of this interesting concept many years ago in
association with accelerometer design and later heard that it has been
used for accelerometers.
A lot of money and brainpower went into rocket and missile technology a
few decades ago.
This discussion may be old stuff to seismometer designers for all I know,
but maybe not. The reason it may not be used is that most seismometers
are designed to have long natural periods of natural oscillation, which
means that they have heavy masses which are hard to stabilize with a
practical feedback force.
However, if a mass reacting to seismic motion is made small, say on the
order a gram, then positional feedback becomes much simpler. But if the
mass does not actually move, then all sorts of non-linearities can be
eliminated from the instrument. The mass would actually still move of
course but maybe only a micron before the optical feedback loop forces it
back into place, whereas a more conventional instrument would let the
mass swing millimeters and then measure the swings. Another advantage of
a positional resoration feedback seismometer (if I might call it that) is
that the natural period of the seismometer would no longer matter, since
the mass would not be permitted to travel much more than a distance equal
to the noise limit of the mass position detector. This consideration
would be conducive to the construction of physically small and cheap
seismometers with admirable insensitivity to the period of the seismic
disturbance, if my analysis is correct.
Am I out to lunch? Comments please: Yours, Roger Baker
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Re: Seismometer design
Date: Thu, 24 Apr 1997 10:00:59 -0700
At 11:11 AM 4/24/97 -0500, you wrote:
> Zero Motion Feedback Principle for Seismometers?
>
>While pondering seismometer design over the last couple of days, it
>occurs to me that there might be great instrumental advantages to
>introducing a mass position resoration feedback loop into the design.
I agree. This is the principle used in the force-balance seismometers that
several people on the list either have or are building. It is also used by
many commercial seismometers in use today. BTW, this is also the principle
of operation of many digital scales used for weighing.
>Another advantage of
>a positional resoration feedback seismometer (if I might call it that) is
>that the natural period of the seismometer would no longer matter, since
>the mass would not be permitted to travel much more than a distance equal
>to the noise limit of the mass position detector.
My background on this part is a bit weak, but I believe the period actually
still does matter; but only with respect to the design of the feedback
loop. But, at least in my experience, this is an important consideration.
In a few days I'll be finished with details of my design of a similar
instrument. I'll let you know when it's done.
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: Santa Cruz Is. events map
Date: Thu, 24 Apr 1997 11:24:03 -0800
Dave,
I like the way** you are collecting felt information via the web, and
may do something similar here in Alaska. I hadn't realized that
a form could generate an Email message.
**(http://psn.quake.net/dave/qu_form.htm)
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: [Fwd: Re: VOLCANO Disaster movie number reviews]
Date: Thu, 24 Apr 1997 12:45:15 -0700
Too funny not to pass on...
--
---/----
cpw
As a fan of the old Star Trek I have only three grades for
volcano/geology movies/episodes.
The geologist survives B
The geologist survives and gets the girl (boy) A
All other outcomes (usually death) F
Michael J. Carr
Geological Sciences
Rutgers University
New Brunswick, NJ 08903
phone 908-445-3619 fax 908-445-3374
carr@...............
From: watson@................ (Charles Watson)
Subject: Re: Santa Cruz Is. events map
Date: Thu, 24 Apr 1997 12:53:39 -0700
I was cruising around Dave's site this morning.
He has a lot of neat web tricks. Fun to check out
--
---/----
cpw
Dr. John Lahr (USGS-GI Seismologist) wrote:
>
> Dave,
>
> I like the way** you are collecting felt information via the web, and
> may do something similar here in Alaska. I hadn't realized that
> a form could generate an Email message.
>
> **(http://psn.quake.net/dave/qu_form.htm)
>
> JCLahr
message: leave PSN-L
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From: "Francesco Nucera" <donjuan@......>
Subject: about QUAKE_L
Date: Fri, 25 Apr 1997 01:57:16 +0200
Please,
could anybody give me the address to subscrive on "QUAKE-L Earthquake
Discussion List"?
Best regards
Francesco Nucera -Italy-
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From: watson@................ (Charles Watson)
Subject: Re: about QUAKE_L
Date: Thu, 24 Apr 1997 17:09:24 -0700
QUAKE-L Earthquake Discussion List <QUAKE-L@..................>
--
---/----
cpw
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From: David A Nelson <dann@........>
Subject: Re: Santa Cruz Is. events map
Date: Fri, 25 Apr 1997 13:36:57 +1200
John,
I originally tried playing with CGI script to make the form more
like most that are on the web. But I could not get it to work. and then
one nite it struck me .....why not just have the form e-mail the results to
me. It does not have the nice laid out look of the from instead it is in
one long string but is not too bad to read the inputted data.
Unfortunately not one yet has made genuine use of the form to mail me a
felt report..... maybe one day
Html writing for web pages is great fun it is so versatile, but I DON'T
claim to be an expert.
Cheers Dave
PS you are welcome to use my html file and just change the headers etc to
suit your location....
no point re-inventing the wheel
At 11:24 AM 4/24/97 -0800, you wrote:
>Dave,
>I like the way** you are collecting felt information via the web, and
>may do something similar here in Alaska. I hadn't realized that
>a form could generate an Email message.
>**(http://psn.quake.net/dave/qu_form.htm)
>
>JCLahr
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
SOD'S LAW--
When Something Does Go Wrong, There Is Sod All You Can Do About It
When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Stephen Paul <spaul@............>
Subject: Re: Seismometer design
Date: Fri, 25 Apr 1997 05:05:23 -0700
roger baker wrote:
>
> Zero Motion Feedback Principle for Seismometers?
>
> While pondering seismometer design over the last couple of days, it
> occurs to me that there might be great instrumental advantages to
> introducing a mass position resoration feedback loop into the design.
> This would give the result that the moving mass usually associated with
> seismometers is kept stationary by imposing a force, especially an
> opposing magnetic force, generated with a sensitive motion detector and
> an amplified feedback loop.
>
> Am I out to lunch? Comments please: Yours, Roger Baker
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
No, Rog, You are not out of your mind (on this subject, at any rate IMO
<g>).
I think your best bet would be to use some form of ring laser gyro or
RLG which is now a common part in what used to be mechanical inertial
guidance platforms, (a little gizmo with gyros and a ball and stuff like
what we like to play with,) formerly used on commercial airlines and
missile systems to position the projectile from an initial fixed point,
which, after much swearing and calibration ( though not neccessarily in
that order, ) the IGP would be closed up, and from then on, any further
change in the platform's position would be logged and compared to the
original cal. and from this, precession would be errored out as much as
possible, and the other various resulting errors, leaving, By the Grace
of God, the position. (Hopefully not a bogey at 9 o' up your tail...)
Flaws: gyroscopic precession
possible and probable miscalibration
only good for so many hours before cumulative errors become
uncorrectable
The RLG (Ring Laser Gyro) solved many of these problems by minimizing
moving parts and computing the phase-shift of a pair of lasers fed
through glass fibres in the form of a ring within a black triangle. Any
such shift would then represent to a fine degree (the 1/2 wavelength of
the laser frequency, I would imagine, (red from a He-Ne or the average
visible-light semiconductor laers, especially back then....being about
615-632 nM then just /2 and stir lightly, or, say 309 nM, which is
pretty fine... visible light ends for us in the 350 or 325 range, I
think) and finding an old one of these might not be as hard as you think
considering the missile failure rates and surplus prices on stuff like
that these days.
I've been out of it for awhile, but I would think these days that LAN
and various other GPS (Global Position Systems) now have accuracy and
cal's. that far exceed even the pretty solid interial stability of a
RLG. That's about all I can say or type... but I think that obviously
some kind of electronic stabilizing loop in a servo-feedback
configuration to create a perfectly servo'd out platform in the field
would be very desirable.
1. Various filters could be applied as windows through the
electro-mechanical servo i.e.
2. Hanning, Hammimg, etc. windows coupled through FFT systems on VLSI
DSP's could give resonance info as well as align the ETC or Energy
Time Curve to more precisely self-align even during the event...
3. Little bitty micros could compare the phase and and energy of
various waves by sampling before,
after, (and if desired with all post-processing completed by the
time the signal reaches the gadg. through the mechanical delay
lines)
4. Just about anything else you might want to look at, basically.
5. You're probably wondering "good talk muh man, but kin you walk it?"
Soitenly... f'rinstance,
For a quick example: you couple your gadg, to a platform which is
coupled to the earth through a set of acoustical delay lines consisting
of spring systems, -well- damped and *timed*. of course, which are the
only non acousstical coupling to the earth. You then take a set of
small, powerful electric, geared motors, which could be charged by day
with a batt. and solar-cell system, and at night by batt., then align
the servo phase-lock-loops running the motors to the light-weight
platform delays from the tip of the spring systems to the first gadg.
sensor lines. That way, any vibration coming from the earth has a slight
delay mechanically, which can be selectively left in, or eliminated
completely, so that only the convolution you wish to apply has plenty of
time to do it's thing before it hits your gadg. either right out of Mama
Earth (somewhat impractical) or through the platform totally servo'd out
of the picture, (IOW the platform and its attendant resonances and
errors leading from it's design, materials and so forth will generate a
signature which can be electrically stored and nulled, and all that
comes through are the movements of your gadg...) leaving only the pure
resonances of the roundish, ringing bell of our poor, beleagured
wanderer, (for those who may feel this is an obscure reference, the
Greek of couse -planet- means wanderer.) Forgive me, I have never
written to this group before and I may sound as if I'm telling cows how
to moo. If so, I apologize and risk your enmity in my desire to be
understood <g>.
I'll bet you feel sane -now- dontcha??
--
Stephen :^)
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From: Robert L Barns <75612.2635@..............>
Subject: Mercury tiltmeter
Date: 25 Apr 97 11:13:20 EDT
Hi gang,
Greg Lyzenga sent me a description of the mercury tiltmeter at Harvey Mudd
Coll. I found it very interesting and am forwarding it to the net.
I recorded a nice quake--4/23 with the LQ here at 1:06 UTC. It has a
sig/noise of about 5 and the surface waves were above bg for about 25 mins.
Bill Scolnik in Oakland NJ also got it. <I did not find it on any official
list.> It would be pretty exciting if this turned out to be local but the only
reports I know of from LaMont are at least 6 months late. Does anyone know of a
source of up-to-date reports about the northeast US and adjacent Canada?
Bob Barns Berk. Hts., NJ
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From: Robert L Barns <75612.2635@..............>
Subject: Mercury tiltmeter
Date: 25 Apr 97 11:13:24 EDT
FROM: Greg Lyzenga, INTERNET:lyzenga@.................
TO: Robert L Barns, 75612,2635
DATE: 4/21/97 12:19 PM
Re: Re: Force Balance article
Sender: lyzenga@.................
Received: from Thuban.AC.HMC.Edu (Thuban.AC.HMC.Edu [134.173.53.8]) by dub-img-2.compuserve.com (8.6.10/5.950515)
id MAA13872; Mon, 21 Apr 1997 12:20:41 -0400
Received: from [128.149.70.7] (zemlya.jpl.nasa.gov)
by THUBAN.AC.HMC.EDU (PMDF V5.1-5 #18017)
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75612.2635@............... Mon, 21 Apr 1997 09:20:36 PDT
Date: Mon, 21 Apr 1997 09:20:30 -0700
From: Greg Lyzenga <lyzenga@.................>
Subject: Re: Force Balance article
In-reply-to: <970421002118_75612.2635_GHL73-1@..............>
To: Robert L Barns <75612.2635@..............>
Message-id: <l03102802af813730fcae@..............>
MIME-version: 1.0
Content-type: text/plain; charset="us-ascii"
>Greg,
> I can't answer your question about the article reference but I have a few of
>my own.
> Somewhere I read that the Harvey Mudd Coll. uses a mercury tiltmeter as a
>seismometer. If so: 1. Is this a commercial device? If so, who made it? 2.
>Could you tell us about it--size, period, performance, stability, etc. etc.?
> One of these is described in great detail in Sci. Am. mag., Nov. 1973
>p124...
>and sounds easy to make and capable of good performance. Is your sensor like
>this one? I am also interested in your opinion of this article.
>Bob Barns
>
Hi Bob:
I'm responding to you directly rather than through the PSN list, on the
assumption that you wanted some background info, but didn't necessarily
want to clog the PSN list with chatter. However, if you think this would
be of general interest, feel free to re-post it (or any fraction thereof).
Yes, at HMC we are operating a pair of mercury tiltmeters as long-period
horizontal seismometers. For a little(!) more information and a look at
the data, browse http://www.physics.hmc.edu/research/geo/seismo.html. The
overall description and design are quite similar to that described in the
1973 Sci. Am. article. Each instrument has a baseline between mercury
reservoirs of roughly two feet, and a capacitance bridge circuit is used to
sense relative changes in level between the two cisterns. Damping is
adjusted via a valve that regulates the flow rate through the tube
connecting them.
I joined the faculty at HMC seven years ago, and it appears that the
instruments had been in operation since sometime in the mid-1970's. It is
possible that their design and construction were directly inspired by the
Sci. Am. article, although I have no direct evidence to that effect.
Unfortunately, when I arrived at HMC, there was little or nothing in the
way of documentation on the instruments; I don't even have a schematic of
the electronics! So it has been a bit of a headache to reverse-engineer
these things to come up with decent calibrations, etc.
The instruments are commercial in the sense that they were fabricated by an
engineering firm in Pomona, CA called Schweim (I think). However, they
appear to be one-of-a-kind jobs, rather than any production model. When I
once tried to contact the company for any information they might have about
the instruments' pedigree, I talked to one semi-retired fellow who vaguely
remembered something about them, but couldn't produce any written
documentation either. Given all this history, you can perhaps understand
my interest in chucking the whole mess in favor of modern broad-band
instruments, if possible.
A few comments on the performance... The overall sensitivity of the
instrument at teleseismic frequencies is good, but not fantastic. My
experience has been that its detection threshold for distant events is just
about the same as my cruddy old homemade Lehman in the garage at home.
Interesting, but not what I would call professional quality. On the other
hand, it is entirely possible that with improved electronics and better
environment, the noise level might be significantly reduced and the useful
sensitivity improved. While the instrument is subject to some
high-frequency noise (ripples in the mercury pools?), that seems to be
beatable with electronic filtering. Low-frequency noise however is also
present. Microseisms are something we can't do a lot about near the coast
(besides filtering), but there is a lot of thermal and cultural noise, too.
People walking in or near the lab where the instrument pier is cause
deflections, not unlike those from a Lehman. The thermal fluctuations are
much larger though, sometimes amounting to a significant fraction of the
full recording dynamic range. This can be a pain. I have not so far been
able to determine whether the drift is internal to the instrument, or
caused by thermally-induced warping of the building foundation. Either
might be possible.
I hope this information is enough to answer most of your first-order
questions. Feel free to ask me for more. I think that this type of
instrument is interesting, but if what you want is a good long-period
horizontal seismometer, there are solutions out there that are considerably
less hassle, more sensitive and more cost-effective.
- Greg
|Gregory A. Lyzenga <lyzenga@.................> *** (909) 621-8378
|Dept. of Physics, Harvey Mudd College *** fax (909) 621-8887
|Claremont, CA 91711-5990
http://www.physics.hmc.edu/profs/lyzenga.html
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From: Edward Cranswick <cranswick@........>
Subject: Re: Mercury tiltmeter
Date: Fri, 25 Apr 1997 12:04:01 -0600
Bob-
I have forwarded your question about seismic info for NE North Armerica
to various people. Lamont doesn't put anything out on the Web
near-realtime?
-Edward
Robert L Barns wrote:
>
> Hi gang,
> Greg Lyzenga sent me a description of the mercury tiltmeter at Harvey Mudd
> Coll. I found it very interesting and am forwarding it to the net.
> I recorded a nice quake--4/23 with the LQ here at 1:06 UTC. It has a
> sig/noise of about 5 and the surface waves were above bg for about 25 mins.
> Bill Scolnik in Oakland NJ also got it. <I did not find it on any official
> list.> It would be pretty exciting if this turned out to be local but the only
> reports I know of from LaMont are at least 6 months late. Does anyone know of a
> source of up-to-date reports about the northeast US and adjacent Canada?
>
> Bob Barns Berk. Hts., NJ
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
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From: "Rev. Bob Shannon" <rshannon@.......>
Subject: Declination?
Date: Fri, 25 Apr 1997 11:07:54 -0700 (PDT)
In adjusting my zenith potentiometer, I have found that using a scope is
the easiest, however I cannot find any ref. to the westerly declination of
my area. Can someone put me in touch with a web page which lists magnectic
westerly declination for Spokane.
Bob
Pinpoint Newsletter
------------------------------------------------------------------
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From: Edward Cranswick <cranswick@........>
Subject: Re: Santa Cruz Is. events map
Date: Fri, 25 Apr 1997 12:13:29 -0600
Dave-
Have you check out this site in which they describe an intensity study
of the 3 May 1996 Duvall Earthquake in near Seattle (i.e., near Bill
Gates) based on felt reports transmitted over the Web?
-Edward
http://www.geophys.washington.edu/SEIS/EQ_Special/Duvall/duval.html
David A Nelson wrote:
>
> John,
> I originally tried playing with CGI script to make the form more
> like most that are on the web. But I could not get it to work. and then
> one nite it struck me .....why not just have the form e-mail the results to
> me. It does not have the nice laid out look of the from instead it is in
> one long string but is not too bad to read the inputted data.
> Unfortunately not one yet has made genuine use of the form to mail me a
> felt report..... maybe one day
> Html writing for web pages is great fun it is so versatile, but I DON'T
> claim to be an expert.
>
> Cheers Dave
>
> PS you are welcome to use my html file and just change the headers etc to
> suit your location....
> no point re-inventing the wheel
>
> At 11:24 AM 4/24/97 -0800, you wrote:
> >Dave,
> >I like the way** you are collecting felt information via the web, and
> >may do something similar here in Alaska. I hadn't realized that
> >a form could generate an Email message.
> >**(http://psn.quake.net/dave/qu_form.htm)
> >
> >JCLahr
> Dave A. Nelson
>
> 24 Jensen St.,
> Green Is., Dunedin,
> South Is.. New Zealand.
>
> http://psn.quake.net/dave/home.htm ( world wide access )
> http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
>
> SOD'S LAW--
> When Something Does Go Wrong, There Is Sod All You Can Do About It
>
> When The Last Of Ten Screws Has Been Removed From A Cover, It Will Be
> Discovered That The Wrong Cover Has Been Removed
>
> When The Last Of Ten Screws Has Been fitted back Into A Cover, It Will Be
> Discovered That The gasket Has Been Left Out
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
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From: roger baker <rcbaker@........>
Subject: General instrumentation
Date: Fri, 25 Apr 1997 13:29:56 -0500 (CDT)
Friends,
Forgive the long post. I'll keep it shorter next time; a few
opening comments and then on to the fun stuff.
Not to toot my own horn, but purely by way of introduction, I am an old
fart instrumentationist who cut his teeth on the old S.A. Amateur
Scientist column in the good ol days and never quite got over it. I not
only corresponded frequently with the uniquely saintly editor, C.L.
Strong, published there several times and have learned a lot since. I am
thrilled to find this discussion group because there are obviously a
bunch of guys (and girls?) out there on this listserver who take homebrew
scientific instrument design very, very seriously. Im personally much
more attracted to clever innovative sealing wax and bailing wire
approaches than shiny complex instruments that took six months and a
machine shop to build. I now do a column called Science Hacker in the
Society for Amateur Scientists Bulletin edited by Jack Herron in Tucson
that deals with everthing from tracking insects to cheap prototyping
strategies.
In this spirit, I love cheap easy to build projects that compete against
$10,000 instruments but am reluctant to take on any project that costs
more than $100, say, or takes more than a few days to build from easy to
get parts. It drives some of my engineering friends up the wall, but I
actually prefer to design with parts from Radio Shack when possible
because it means that anyone can easily duplicate projects.
But back to matters at hand. It does seem that a mercury tiltmeter could
be easily be built with some other conductive fluid such as glycol
antifreeze or glycerine, water and a little salt. Mercury is expensive
and poisonous but capacitance micrometry should work with any conductive
fluid to give an extremely sensitive tiltmeter, although the best tiltmeter
might not work so well as a directional seismometer; you tell me.
The old British Journal of Physics series dealing with scientific
instrumentation had some articles on capacitance micrometry by an
extremely clever fellow named R. V. Jones ( who helped develop British
radar during W W II; pester me and Ill dig up the exact reference). It
turns out that anyone can build an extremely sensitive capacitance bridge
working at about 10 khz. You filter the imbalance signal and then use a
synchronous detector to get more sensitivity than anyone will probably
need; that is many orders of magnitude less than one Angstrom of average
deplacement of the plates. You nearly always use two identical
symmetrical capacitors and often use then in a push pull arrangement to
measure the motion of a sensing plate sandwiched between two other
plates. Anyone trying to measure very small displacements should consider
that they can build a capacitance micrometer fairly easily and cheaply
with common parts.
Those who pride themselves on having built sensitive seismometers might
want to tackle something really tough--a tidal gravimeter able to measure
the diurnal milligal fluctuations in gravity due to the sun and moon. I
almost did it before realizing that any vertical accelerometer (and
vertical axis seismograph by implication) sensitive enough to do the job
must have extremely low drift over a day and must therefore the enclosed
in a very good temperature controlled surrounding--perhaps on the order
of millidegees Centigrade.
Almost all sensitive electronic and scientific instruments are actually
thermometers, and you can get an order of magnitude improvement of
accuracy by putting everything in a metal box, and maintaining everything
a little above ambient temperature with a thermostatic feedback loop.
Strange they forget to tell you this in physics/engineering class.
This is not too hard to do, but it meant that I would have to go off on
another tangent of instrument design. I made the mistake of trying to
enclose the instrument in a cooler surrounded by crushed ice, which meant
that every time the ice melted it shifted and created lots of noise; ice
is not nearly so good in practice as in theory as a way to easily
stabilize temperature.
But at any rate, my vertical acceleratometer/gravimeter design is very
nice and easy to build, as I have posted recently. It uses a tiny iron
weight weighing perhaps 50 milligrams on the end of a glass fiber, the
weight of which is very nearly balanced by a magnetic field created by an
ajustable position large ceramic magnet. Therefore this would not make a
good field instrument because of the directional variation in the earths
magnetic field, but it is appropriate to a stationary gravimeter or
seismograph.
In a sense it was inspired by the Worden gravimeter which has a very tiny
moving mass while remaining very sensitive, and points the way in good
design in this regard, except that it is hard to build from silica
filaments. The LaCoste Romberg company here in Austin makes gravimeters
according to the zero length spring principle invented by Prof. La Coste
at the University of Texas in the 1930s. These instruments, and almost
all gravimeters (which are often used as portable field instruments for
petroleum exploration because they can help locate salt domes), rely on
clever spring arrangements to very nearly balance the force of gravity on
a mass rather than a magnetic field, as I used, to achieve their high
sensitivity.
I think if I were to develop my vertical seismograph further according to
the very instrumentally attractive force balance principle, I would use a
little rare earth magnet from Radio Shack instead of the iron mass on the
end of my horizontal glass filament and then use force feedback from a
tiny flat pancake coil mounted just over this magnet. This same coil
would both attract and repel the little magnet in equal measure according
to its energizing current and polarity. Therefore you would not have to
have two separate coils on either side of an iron mass to give the needed
force feedback. Meanwhile, as before the magnetic field induced by the
large ceramic magnet would just balance the force of gravity on the
little rare earth magnet as with the small iron mass in my original
gravimeter/vertical seismograph, which I built about a year ago. As I
said earlier, the instrument is cheap and easy to build and its
sensitivity is good enough to see constant seismic background noise in
the central Austin area where I live.
My impression is that one axis horizontal seismographs are substantially
easier to build than vertically sensitive instruments due to the physics
involved, and that two axis instruments need not be too much harder than
one axis horizontal instruments. But here I am well out of my area of
expertise and can only listen in awe to you pros out there. I do not even
know what a Lehman seismomter is.
Just for kicks, and for the keenest minds out there, I have a
magnetometer puzzle that has stumped the best. I promise it can be
solved. You have two small ceramic wafer magnets. The problem is to use
one to detect the presence of the other at a range of ten feet!
Obviously, their interaction force drops off as the cube of the distance
separating the two, so some quite sensitive method is involved. Yet you
can set up an experiment with stuff that you normally find around the
house in an hour or so to use one to detect the field of the other at a
distance of ten feet or more. So how do you do it? Post
to me direct to avoid clutter and I'll tell you all eventually.
--Yours, Roger Baker; Science Hacker
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From: esssa_abstracts@.................. (Bob Wetmiller)
Subject: Re: [Fwd: Mercury tiltmeter]
Date: Fri, 25 Apr 1997 15:53:07 -0400
Re: query by Bob Barns Berk. Hts., NJ
Earthquake reports from Canada (Geological Survey of Canada) are
available via finger at:
quake@..................
We know of no local event around the time (4/23 1:06 UTC) mentioned
and see no seismic event matching the description given. Not sure
what the source of the event seen in NJ could be.
Bob Wetmiller
Ottawa
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From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: Felt Information Email
Date: Fri, 25 Apr 1997 13:19:02 -0800
Dave,
Thanks for coming up with this technique! It's more
straight forward than a perl script would be. I'll
let you know when I have my version done (it could be
a while!).
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
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Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: Felt Information Email
Date: Fri, 25 Apr 1997 14:34:38 -0700
Heck, I thought Dave's felt page was so nifty, I copied the script and
modified to the Seismo-Watch style:
http://www.seismo-watch.com/EQSERVICES/SeismoFeatures/FeltQuake.html
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
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Public Seismic Network Mailing List (PSN-L)
From: Robert Avakian <ravakian@............>
Subject: Re: Declination?
Date: Fri, 25 Apr 1997 11:54:10 -0700
Rev. Bob Shannon wrote:
>
> In adjusting my zenith potentiometer, I have found that using a scope is
> the easiest, however I cannot find any ref. to the westerly declination of
> my area. Can someone put me in touch with a web page which lists magnectic
> westerly declination for Spokane.
> Bob
> Pinpoint Newsletter
> ------------------------------------------------------------------
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
Go to your nearest library or outdoor store and get a look at a topo map
for your area. The info is on the bottom.
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From: "Rev. Bob Shannon" <rshannon@.......>
Subject: Re: Declination?
Date: Fri, 25 Apr 1997 16:55:33 -0700 (PDT)
On Fri, 25 Apr 1997, Robert Avakian wrote:
> Rev. Bob Shannon wrote:
> >
> > In adjusting my zenith potentiometer, I have found that using a scope is
> > the easiest, however I cannot find any ref. to the westerly declination of
> > my area. Can someone put me in touch with a web page which lists magnectic
> > westerly declination for Spokane.
> Go to your nearest library or outdoor store and get a look at a topo map
> for your area. The info is on the bottom.
Spokane Library has no map section...the Eastern Washington University Map
Section is in disarray due to rebuiding and poor help- Two outdoor stores
REI and the Outdoorsman, had clerk help who were underpaid and
overworked...besides they had no idea of what declination might be, nor
where to find a map...So....Question still remains valid...W Declination
for Spokane area? Anyone?
Bob
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From: Ron Westfall <westfall@......>
Subject: Re: Declination?
Date: Fri, 25 Apr 1997 19:18:09 -0700
Rev. Bob Shannon wrote:
>
> > Go to your nearest library or outdoor store and get a look at a topo map
> > for your area. The info is on the bottom.
>
> Spokane Library has no map section...the Eastern Washington University Map
> Section is in disarray due to rebuiding and poor help- Two outdoor stores
> REI and the Outdoorsman, had clerk help who were underpaid and
> overworked...besides they had no idea of what declination might be, nor
> where to find a map...So....Question still remains valid...W Declination
> for Spokane area? Anyone?
The first responder is correct. The only way to find out is using a
topographic map for the area. Declination will be different for
locations
as little as 20 - 50 miles apart. A vendor of compasses states on
their web
page that declination "varies by as much as 42 degrees from coast to
coast".
As the first responder suggested, declination might be on the bottom
of the
map. The other technique I have seen is to have a compass rose on one
or more
spots on the map. The declination is printed on the N - S axis of the
rose.
Printing it on the bottom of the map works for detailed maps that
cover a
limited area. The compass rose approach works best for maps covering
a larger
area.
To find a topographic map dealer in your area, check out www.usgs.gov
and
follow the appropriate references. For Spokane I found in addition to
REI:
Northwest Interpretive Assoc.
Spokane Information Office
400 S. Jefferson, Ste. 106
Northwest Map Travel Center
525 W. Sprague Ave.
(509) 455-6981
I posted this message to the list rather than Bob directly, because
everybody
should understand the significance of declination. In case there is
anybody
who has not encountered declination recently, it is the difference in
degrees
between magnetic north and true north (defined by Earth's axis of
spin).
Declination varies from location to location. Declination can change
dramatically in a localized area due to magnetic anomalies.
Declination also
changes a small amount each year due to movement of the magnetic north
pole.
This annual change is marked on the map alongside the declination.
Since the
change can add up to significant amounts, it should always be taken
into
account.
Given the "unreliable" nature of magnetic north, most disciplines
interested
in direction use true north as their reference. In seismology, I
would expect
that the USGS seismographs are oriented relative to true north rather
than
magnetic north. Using true north is only way that data from two or
more
stations can be correlated. I would expect that most amateurs would
similarly
want to orient their seismographs using true north as the reference.
You may have noticed that I said "I expect" true north to be used as
the
reference. I don't have any certain knowledge this is the case, but
it seems
highly likely. Would any of the USGS people care to comment?
Ron Westfall
westfall@......
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Public Seismic Network Mailing List (PSN-L)
From: David Josephson <david@...............>
Subject: Re: Declination?
Date: Fri, 25 Apr 1997 19:38:57 -0700 (PDT)
> > Rev. Bob Shannon wrote:
> > >
> > > In adjusting my zenith potentiometer, I have found that using a scope is
> > > the easiest, however I cannot find any ref. to the westerly declination of
> > > my area. Can someone put me in touch with a web page which lists magnectic
> > > westerly declination for Spokane.
>
> > Go to your nearest library or outdoor store and get a look at a topo map
> > for your area. The info is on the bottom.
>
> Spokane Library has no map section...the Eastern Washington University Map
> Section is in disarray due to rebuiding and poor help- Two outdoor stores
At http://julius.ngdc.noaa.gov/seg/potfld/geomag.html you can find
the NOAA's GEOMAG program that will give you declination, inclination,
and a reasonable guess at x, y, z, and total field magnetic values
for any point; there is also a link to the Tiger database which
will retrieve lat and long for any town name.
For 47.25 N, 122.45 W and today, it says D is 9 degrees 29.3 minutes west,
and is expected to change by half a minute per year, east..
You can also download a copy of GEOMAG to run on your own PC.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Mercury tiltmeter
Date: Sat, 26 Apr 1997 18:02:45 +1200
Greg,
the tilt meter pages are unaccessable www error 404 comes up
the other HMC pages are ok
Dave Nelson
SNIP
>Yes, at HMC we are operating a pair of mercury tiltmeters as long-period
>horizontal seismometers. For a little(!) more information and a look at
>the data, browse http://www.physics.hmc.edu/research/geo/seismo.html. The
>overall description and design are quite similar to that described in the
>1973 Sci. Am. article. Each instrument has a baseline between mercury
>reservoirs of roughly two feet, and a capacitance bridge circuit is used to
>sense relative changes in level between the two cisterns. Damping is
>adjusted via a valve that regulates the flow rate through the tube
>connecting them.
>
>SNIP
Greg
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Santa Cruz Is. events map
Date: Sat, 26 Apr 1997 18:30:37 +1200
Not bad great response eh Edward, I would be happy with a fraction of
that oh well maybe one day...
a pity they didn't seem to have the report form around any more (well I
couldn't find it ) would have been good to see how they did it
Dave
At 12:13 PM 4/25/97 -0600, you wrote:
>Dave-
>Have you check out this site in which they describe an intensity study
>of the 3 May 1996 Duvall Earthquake in near Seattle (i.e., near Bill
>Gates) based on felt reports transmitted over the Web?
>-Edward
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Dennis Leatart <ASTROSEEK@.........>
Subject: We got hit by a big one!!!
Date: Sat, 26 Apr 1997 03:53:02 -0700
OK guys who turned on the roller coaster???? First time in a long
time have I seen the screen go side to side!!! No location yet!!!
Will keep you posted--it was a close one, that's for sure!!! Mom said
it was a 5.0!!! got a good trace!!! Full scale! Will post more later
when I find out more!!!
--
_____ __
| \.-----.-----.-----.|__|.-----.
| -- | -__| | || ||__ --|
|_____/|_____|__|__|__|__||__||_____|
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: We got hit by a big one!!!
Date: Sat, 26 Apr 1997 02:58:25 -0700
This is from the caltech.edu finger service:
97/04/26 10:37:30 34.37N 118.67W 15.5 5.0MLG A 7 mi. NNE of SIMI VALLEY
97/04/26 10:40:29 34.37N 118.67W 14.5 4.0MLG A* 7 mi. NNE of SIMI VALLEY
-Larry
At 03:53 AM 4/26/97 -0700, you wrote:
>OK guys who turned on the roller coaster???? First time in a long
>time have I seen the screen go side to side!!! No location yet!!!
>Will keep you posted--it was a close one, that's for sure!!! Mom said
>it was a 5.0!!! got a good trace!!! Full scale! Will post more later
>when I find out more!!!
>
>--
> _____ __
>| \.-----.-----.-----.|__|.-----.
>| -- | -__| | || ||__ --|
>|_____/|_____|__|__|__|__||__||_____|
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: felt report
Date: Sat, 26 Apr 1997 23:44:25 +1200
from Russell J De Ment
email=rjd@............
name=Russ De Ment
Ft=4/26/97 3A40 p.s.t.
lgth=5
rmbl=DURING
shk1=LIGHT
shk2=SHUDDER
dam=NONE
dam1=NONE
text=Dont know if you are tracking California stuff, but
Woke up about 5 minutes before ( 28alergy 29) ?? and was making some tea.
Was about 2 seconds between a small jolt and the shaking of about 3 seconds
more.
My location dont have coords. but is on the rim of Pickens Canyon, on the
La Crescent
Canada border in California, which about 3 miles north of JPL and about 15
miles south of
Northridge. Had a small aftershock at about 3A45. My guess is that it was
about a 3.6
aftershock of the Northridge quake. Time between P and S felt about the
same as those did.
cheers Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: seismocam
Date: Sat, 26 Apr 1997 23:55:26 +1200
here it is in real time updated every 5 minutes you can see tonites events
http://www.knbc4la.com/seismo/images/seismoNow.jpg
enjoy Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: aftershock
Date: Sun, 27 Apr 1997 00:12:26 +1200
just a few minutes ago ~1205 utc caught the seismo cam in the middle of
another a.shock
dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: the list so far
Date: Sun, 27 Apr 1997 00:27:18 +1200
97/04/26 10:37:30 34.37N 118.67W 15.5 5.0MLG A 7 mi. NNE of SIMI VALLEY
97/04/26 10:40:29 34.37N 118.67W 14.5 4.0MLG A 7 mi. NNE of SIMI VALLEY
97/04/26 10:53:42 34.37N 118.67W 19.0 2.4MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 10:54:30 34.39N 118.65W 11.5 3.2MLG A 7 mi. W of NEWHALL
97/04/26 10:57:55 34.37N 118.66W 18.9 2.6MLG A* 7 mi. W of NEWHALL
97/04/26 11:08:55 34.39N 118.66W 13.3 2.6MLG A* 8 mi. SSW of CASTAIC
97/04/26 11:10:04 34.38N 118.65W 11.9 3.2MLG A 7 mi. W of NEWHALL
97/04/26 11:16:18 34.38N 118.66W 13.8 2.6MLG A* 8 mi. SSW of CASTAIC
97/04/26 11:16:43 34.38N 118.68W 17.0 2.1MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 11:33:37 34.38N 118.65W 12.8 3.2MLG A 7 mi. W of NEWHALL
97/04/26 11:55:47 34.38N 118.67W 14.5 3.8MLG A 8 mi. NNE of SIMI VALLEY
97/04/26 12:01:56 34.38N 118.67W 17.1 2.4MLG A* 8 mi. NNE of SIMI VALLEY
97/04/26 12:21:24 34.38N 118.67W 15.8 2.6MLG A* 7 mi. NNE of SIMI VALLEY
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Dennis Leatart <ASTROSEEK@.........>
Subject: Simi Valley Quake--5.0
Date: Sat, 26 Apr 1997 10:11:43 -0700
Hi!!!
If any of you would like a copy of the 5.0 and subsequent 4.0 from a
vantage point of about 11 miles from the epicenter, I have converted it
to a bitmap file which can be read by most paint programs. Be warned,
however, that the file is about 420 KBytes.
--
_____ __
| \.-----.-----.-----.|__|.-----.
| -- | -__| | || ||__ --|
|_____/|_____|__|__|__|__||__||_____|
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: roger baker <rcbaker@........>
Subject: Re: We got hit by a big one!!!
Date: Sat, 26 Apr 1997 12:15:34 -0500 (CDT)
Friends,
It is starting to occur to me that any idiot can build a pretty
sensitive seismometer, but nobody can quite figure out what the data
means. The implication of this, I suppose, is that somebody should come
up with a $20 instrument that you can scatter around like jellybeans and
link them up with a computer network. At this point everything turns into
mathematics, which I'm terrible at. But I think I might be pretty good at
designing the jellybeans.
The really interesting question to me right now is if you design a
range of sizes of seismometers using the force feedback principle, is
there any practical loss of sensitivity when you make them very small?
For example, could you build arrays of accelerometers on silicon chips that
would be as sensitive as the massive old instruments? If not, exactly what
physical laws stand in the way? It seems like very small sensing masses
mounted on quartz fibers or their equivalent, the use of active force
balancing, and capacitive displacement sensing is the way to go. So what
prevents you from designing a chip or at least a pocket sized instrument
that could do the job of the old monsters? As you know, you can increase
the sensitivity of any sensor by two by building four identical sensors
and averaging their responses, or by ten by building 100, etc. This is
the way the ear gets its sensitivity I think--by having lots of sensing
hairs in parallel. But notice that the motion sensing hairs in the ear are
all different lengths, as well as being the most sensitive microphone known.
By analogy, if you could build very small cheap accelerometers,
or micro-seismometers, you would probably try to build them tuned to
many different frequencies to maximize their inherent sensitivities. If
you use the force feedback principle, is damping still helpful, or would
you rather enclose the micropendulum in a vacuum, as I suspect?
--Yours, Roger
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: recent "Northridge Aftershock"?
Date: Sat, 26 Apr 1997 10:36:47 -0700
By the way everyone, notice the depth of the recent "Northridge M5.0
Aftershock" quake is 15.5 km at the northwestern margin of the
aftershock zone. If the initial rupture plane dipped to the
south-southwest and the hypocenter was below Northridge at ~14.7 km,
today's hypocenter is along another fault plane below and perhaps
subparallel to the mainshock plane. Although aftershock activity along
this adjacent fault plane is not uncommon, it is very intersting to
think about potential magnitude calculations assigned of specific faults
given a predetermined length, heigth, and displacement of a single
rupture surface, when accuality it is much more complex than that.
Could it be that we are underestimating our recommendations to our
engineers by a significant margin? Remember the Landers M7.1 earthquake
ruptured several noncontiguiuos faults to form magnitude Mw 7.3 when
each of the faults in the area was given a maximum potential magnitude
of M6.0-6.5!
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
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Public Seismic Network Mailing List (PSN-L)
From: Greg Lyzenga <lyzenga@.................>
Subject: Re: Mercury tiltmeter
Date: Sat, 26 Apr 1997 10:59:38 -0700
>Greg,
> the tilt meter pages are unaccessable www error 404 comes up
>
> the other HMC pages are ok
>
> Dave Nelson
>
>
Yes, thanks. As it turns out, the updating of these pages depends on an
automatic script running on another computer over the local network. When
network problems or outages occur (as they do with distressing regularity)
sometimes the latest data gets dropped. However, only the display is lost;
the actual original data are safe and sound.
As of this morning, all the channels appear to be displaying. We got a
good recording (but clipped!) of this morning's M 5.0 southern California
quake. Quite a few folks (myself included) had their sleep interrupted!
Thanks for the message.
- Greg
|Gregory A. Lyzenga <lyzenga@.................> *** (909) 621-8378
|Dept. of Physics, Harvey Mudd College *** fax (909) 621-8887
|Claremont, CA 91711-5990
http://www.physics.hmc.edu/profs/lyzenga.html
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Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Santa Cruz Is. events map (Intensity Form)
Date: Sat, 26 Apr 1997 15:49:51 -0600
Dave-
I forwarded a couple copies of John Lahr's letter about your Web
Intensity Form to NEIC people upstairs, and that got them interested in
the PSN. So one day you'll get a large local event, and you will be so
deluged you'll wish you never said nothin ...
-Edward
David A Nelson wrote:
>
> Not bad great response eh Edward, I would be happy with a fraction of
> that oh well maybe one day...
>
> a pity they didn't seem to have the report form around any more (well I
> couldn't find it ) would have been good to see how they did it
>
> Dave
>
> At 12:13 PM 4/25/97 -0600, you wrote:
> >Dave-
> >Have you check out this site in which they describe an intensity study
> >of the 3 May 1996 Duvall Earthquake in near Seattle (i.e., near Bill
> >Gates) based on felt reports transmitted over the Web?
> >-Edward
> >
> Dave A. Nelson
>
> 24 Jensen St.,
> Green Is., Dunedin,
> South Is.. New Zealand.
>
> http://psn.quake.net/dave/home.htm ( world wide access )
> http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
>
> When The Last Of Ten Screws Has Been Removed From A Cover,
> It Will Be Discovered That The Wrong Cover Has Been Removed
>
> When The Last Of Ten Screws Has Been fitted back Into A Cover,
> It Will Be Discovered That The gasket Has Been Left Out
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re Intensity Form
Date: Sun, 27 Apr 1997 12:20:00 +1200
It has started already, Ed, I have had two posts for last nite south Cal.
event
TNX Dave
At 03:49 PM 4/26/97 -0600, you wrote:
>Dave-
>I forwarded a couple copies of John Lahr's letter about your Web
>Intensity Form to NEIC people upstairs, and that got them interested in
>the PSN. So one day you'll get a large local event, and you will be so
>deluged you'll wish you never said nothin ...
>-Edward
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: another felt report
Date: Sun, 27 Apr 1997 12:34:41 +1200
here is a felt report from Wayne H. Francis
email=francis@.............
name=Wayne H. Francis
loc=Oja, CA
d/t=0338 PST, 04/26/97
lgth=5
rmbl=NONE
shk1=LIGHT
shk2=HORIZONTAL+SHK
dam=NONE
dam1=NONE
text=Just a gentle shaking that woke me from sleep. Did not wake the wife
or kids. Only lasted a few seconds, but coming out of sleep, don't know
what I may
have missed.
I'm not sure where Oja is maybe you guys do
TNX wayne for the report
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: 1990 PSN proposal (Re: We got hit by a big one!!!)
Date: Sat, 26 Apr 1997 20:00:58 -0600
Roger-
Your post about:
> up with a $20 instrument that you can scatter around like jellybeans
[see full message below]
reminds me of my wet dreams on the subject, "Proposal for a People's
Seismograph Array...", which we presented at the American Geophysical
Union Meeting at San Francisco in December 1990, a year after the Loma
Prieta Earthquake. Unbeknownst to me at the time I wrote the abstract,
Steve Hammond and others of what became the PSN San Jose, were already
doing much of what we proposed. However, the cheap, mass-distributed
seismograph is still virtual. Send me your snail-mail address, and I'll
send you some more hardcopy on the subject.
-Edward
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
A Proposal for a People's Seismograph Array Based on Home Computers in
the San Francisco Bay Area
E. Cranswick
R. Banfill
The widespread use of microcomputers by private citizens and the recent
public awareness of seismic hazard following the Loma Prieta Earthquake
suggest a new method of monitoring seismological phenomena in the San
Francisco Bay Area. It is technically feasible to build a
self-contained digital seismic data acquisition unit (SDAU) that would
utilize the modem of a home computer (Macintosh or IBM-PC-compatible*)
to communicate seismic information to a central processing/archival
system (CPAS) minicomputer located at the U. S. Geological Survey in
Menlo Park, California. There are approximately 100,000 home
microcomputers within a 100 km radius of Menlo Park. If 1% of these
users were to participate in the program described here, and if half of
those regularly generated reliable data, the resulting array would have
an average inter-station spacing of ~8 km. The SDAU would digitize
seismic signals from a 3-component FBA sensor buried immediately outside
the residence and scan these timeseries in realtime for seismic events
which, when detected, would be stored in RAM. A post-processor would
analyze the event timeseries for P- and S-wave phase times, peak
amplitudes, durations, etc., and these event parameters would be
routinely transmitted by the host microcomputer to the CPAS via
telephone. The CPAS, similar to a telephone switching/accounting
computer system, would be equipped with at least 100 input lines and
would maintain an archive of all user calls, i.e., a history of each
station. A clock correction to the internal clock of each SDAU would be
recorded by the CPAS whenever the host microcomputer uploaded event
parameters. Crucial to the success of the proposed data acquisition
scheme would be an effective USGS/SDAU-users group. The users group
would provide software/hardware support and publish a monthly newsletter
which would summarize the results of the array's operation and give
recognition to users distinquished by the completeness and reliabilty of
their data. The integrity of the dataset would be maintained by its
redundancy and by its current and comprehensive station history. The
high spatial density of stations would permit the use of simple methods
of analysis, e.g., tomography and spectral amplitude ratios, and provide
a set of seismic observations which approached the scale of geologic
observations. In an age of government budget deficits, popularity of
High-Tech, and public recognition of the inevitability of earthquakes,
the proposed scheme could provide a similtaneous view of the seismic
source process and the micro-regional site response which is
increasingly critical to life in the San Francisco Bay Area.
* Use of tradenames is for descriptive purposes only and does not imply
an endorsement by the U. S. Geological Survey.
(Cranswick, E., and Banfill, R., 1990, Proposal for a high-density
people's seismograph array based on home computers in the San Francisco
Bay Area: Eos (American Geophysical Union, Transactions), v. 71, no.
43, p. 1469.)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
roger baker wrote:
>
> Friends,
> It is starting to occur to me that any idiot can build a pretty
> sensitive seismometer, but nobody can quite figure out what the data
> means. The implication of this, I suppose, is that somebody should come
> up with a $20 instrument that you can scatter around like jellybeans and
> link them up with a computer network. At this point everything turns into
> mathematics, which I'm terrible at. But I think I might be pretty good at
> designing the jellybeans.
> The really interesting question to me right now is if you design a
> range of sizes of seismometers using the force feedback principle, is
> there any practical loss of sensitivity when you make them very small?
>
> For example, could you build arrays of accelerometers on silicon chips that
> would be as sensitive as the massive old instruments? If not, exactly what
> physical laws stand in the way? It seems like very small sensing masses
> mounted on quartz fibers or their equivalent, the use of active force
> balancing, and capacitive displacement sensing is the way to go. So what
> prevents you from designing a chip or at least a pocket sized instrument
> that could do the job of the old monsters? As you know, you can increase
> the sensitivity of any sensor by two by building four identical sensors
> and averaging their responses, or by ten by building 100, etc. This is
> the way the ear gets its sensitivity I think--by having lots of sensing
> hairs in parallel. But notice that the motion sensing hairs in the ear are
> all different lengths, as well as being the most sensitive microphone known.
> By analogy, if you could build very small cheap accelerometers,
> or micro-seismometers, you would probably try to build them tuned to
> many different frequencies to maximize their inherent sensitivities. If
> you use the force feedback principle, is damping still helpful, or would
> you rather enclose the micropendulum in a vacuum, as I suspect?
>
> --Yours, Roger
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David Alexander <dalex@...........>
Subject: Re: Declination?
Date: Sat, 26 Apr 1997 19:19:26 -0700
try this url and look under declination
http://www.swcp.com/~ab5p/foxhunt.html
it gives a method of finding declination your self with a compass.
dave k7da
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: S. Cal. list updated
Date: Sun, 27 Apr 1997 14:48:44 +1200
97/04/26 10:37:30 34.37N 118.67W 15.5 5.0MLG A 7 mi. NNE of SIMI VALLEY
97/04/26 10:40:29 34.37N 118.67W 14.5 4.0MLG A 7 mi. NNE of SIMI VALLEY
97/04/26 10:53:42 34.37N 118.67W 19.0 2.4MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 10:54:30 34.39N 118.65W 11.5 3.2MLG A 7 mi. W of NEWHALL
97/04/26 10:57:55 34.37N 118.66W 18.9 2.6MLG A* 7 mi. W of NEWHALL
97/04/26 11:08:55 34.39N 118.66W 13.3 2.6MLG A* 8 mi. SSW of CASTAIC
97/04/26 11:10:04 34.38N 118.65W 11.9 3.2MLG A 7 mi. W of NEWHALL
97/04/26 11:16:18 34.38N 118.66W 13.8 2.6MLG A* 8 mi. SSW of CASTAIC
97/04/26 11:16:43 34.38N 118.68W 17.0 2.1MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 11:33:37 34.38N 118.65W 12.8 3.2MLG A 7 mi. W of NEWHALL
97/04/26 11:55:47 34.38N 118.67W 14.5 3.8MLG A 8 mi. NNE of SIMI VALLEY
97/04/26 12:01:56 34.38N 118.67W 17.1 2.4MLG A* 8 mi. NNE of SIMI VALLEY
97/04/26 12:21:24 34.38N 118.67W 15.8 2.6MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 12:29:26 34.37N 118.67W 19.7 2.2MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 12:31:13 34.38N 118.65W 15.1 2.6MLG A* 7 mi. W of NEWHALL
97/04/26 13:02:38 34.36N 118.68W 17.9 2.4MLG A* 6 mi. NNE of SIMI VALLEY
97/04/26 13:08:59 34.37N 118.67W 17.8 2.3MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 14:31:34 34.38N 118.65W 13.2 3.0MLG A 7 mi. W of NEWHALL
97/04/26 15:51:11 34.38N 118.67W 15.5 2.4MLG A* 8 mi. NNE of SIMI VALLEY
97/04/26 16:13:42 34.37N 118.67W 14.6 3.4MLG A 7 mi. NNE of SIMI VALLEY
97/04/26 16:59:15 34.38N 118.67W 15.6 2.0MGN A* 8 mi. NNE of SIMI VALLEY
Cheers Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: relief map of LA region
Date: Sun, 27 Apr 1997 15:02:28 +1200
hi all,
at the top of my quakes page is a relief map showing the recent
events in the hills nth of the San Fernando Valley
http://psn.quake.net/dave/quakes.htm
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: frankcnd@.......... (Frank Condon)
Subject: felt report
Date: xMessageSize=2000000
email=frankcnd@..........
name=Frank Condon
loc=Hesperia, CA
d=04/26/97
t=3:40AM
lgth=10 sec.
rmbl=NONE
shk1=NONE
shk2=HORIZONTAL East-West motion
dam=NONE
dam1=NONE
text=Since I was awake at the time of the earthquake I can report that I
heard a
lot of noise made by birds and dogs just minutes before the event. One of
the birds was making an unusual call that I have not heard before. I was
laying in my bed trying to fall asleep when I felt the 5.0 hit. It felt like
a gentle but steady East to West horizontal motion here and seemed to last
about five-ten seconds. My guess is that it was somewhere on the frontal
fault zone.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: relief map of LA region
Date: Sat, 26 Apr 1997 21:21:10 -0600
Dave-
> at the top of my quakes page is a relief map showing the recent
> events in the hills nth of the San Fernando Valley
>
> http://psn.quake.net/dave/quakes.htm
> When The Last Of Ten Screws Has Been fitted back Into A Cover,
> It Will Be Discovered That The gasket Has Been Left Out
I think that the relief map is missing a gasket.
-Edward
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: relief map of LA region
Date: Sun, 27 Apr 1997 16:42:05 +1200
sorry about the BooBoo with the map I had the html doc saying load a jpg
instead of a gif image
It"s all go now
Dave
At 09:21 PM 4/26/97 -0600, you wrote:
>Dave-
>> at the top of my quakes page is a relief map showing the recent
>> events in the hills nth of the San Fernando Valley
>>
>> http://psn.quake.net/dave/quakes.htm
>
>> When The Last Of Ten Screws Has Been fitted back Into A Cover,
>> It Will Be Discovered That The gasket Has Been Left Out
>
>I think that the relief map is missing a gasket.
>-Edward
>
>--
>Edward Cranswick Tel: 303-273-8609
>US Geological Survey, MS 966 Fax: 303-273-8600
>1711 Illinois St cranswick@........
>Golden, CO 80401 USA E.M. Forster said, "Only connect".
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "wa6sul" <wa6sul@.............>
Subject: Re: S. Cal. list updated
Date: Sat, 26 Apr 1997 22:21:28 -0700
> 97/04/26 15:51:11 34.38N 118.67W 15.5 2.4MLG A* 8 mi. NNE of SIMI
VALLEY
> 97/04/26 16:13:42 34.37N 118.67W 14.6 3.4MLG A 7 mi. NNE of SIMI
VALLEY
> 97/04/26 16:59:15 34.38N 118.67W 15.6 2.0MGN A* 8 mi. NNE of SIMI
VALLEY
>
>
I think it would be fair if you would give credit for the source of this
info.
It looks exactly like that from scec,gps.caltech.edu info available
here to all.
You make it appear as if you are the original source of this info.
Maybe a small point to some, but fairness dictates to all knowlegable.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: relief map of LA region
Date: Sat, 26 Apr 1997 23:58:07 -0600
Dave-
Charlie Watson did the seismotectonic thinking about the significance of
the magnitude 5.
David A Nelson wrote:
>
> sorry about the BooBoo with the map I had the html doc saying load a jpg
> instead of a gif image
> It"s all go now
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Ray Gallagher" <rayban1@.............>
Subject: Re: S. Cal. list updated
Date: Sun, 27 Apr 1997 00:03:35 -0700
wa6sul,
I am sorry, but I think it is so very obvious to everyone where Dave obtain
the updated S. Cal list and I cannot understand how you thought he was
trying to infer he was the source of the information/data??? His post/note
did not come across that way to me at all and I appreciated him posting the
updated list.
To everyone else.. I have found a link where you can obtain earthquake
readings below 2.0 for Southern California. I have been looking for
something like this forever and I was really excited when I found it. Most
or all of you probably already know of the site and I guess I have not been
paying attention. <g> I do not have the URL in front of me right now, but I
have linked it to my recent earthquake page at:
http://www.netcom.com/~rayban1/recentquakes.html (when you get there
choose the second link.. "Southern California/ISAIAH Earthquake Review
List").
Take care & stay safe!
Ray Gallagher
rayban1@.............
http://www.netcom.com/~rayban1/
----------
> From: wa6sul <wa6sul@.............>
> To: PSN-L Mailing List <psn-l@.............>
> Subject: Re: S. Cal. list updated
> Date: Saturday, April 26, 1997 10:21 PM
>
>
>
> > 97/04/26 15:51:11 34.38N 118.67W 15.5 2.4MLG A* 8 mi. NNE of SIMI
> VALLEY
> > 97/04/26 16:13:42 34.37N 118.67W 14.6 3.4MLG A 7 mi. NNE of SIMI
> VALLEY
> > 97/04/26 16:59:15 34.38N 118.67W 15.6 2.0MGN A* 8 mi. NNE of SIMI
> VALLEY
> >
> >
> I think it would be fair if you would give credit for the source of this
> info.
> It looks exactly like that from scec,gps.caltech.edu info available
> here to all.
> You make it appear as if you are the original source of this info.
> Maybe a small point to some, but fairness dictates to all knowlegable.
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: bfryer@............ (Bob Fryer)
Subject: Re: relief map of LA region
Date: Sun, 27 Apr 1997 02:19:07 -0700 (PDT)
Hello Dave & all,
Yes, I pick these up direct from USGS.
Does anyone have anything similar handy for Northridge or Kobe?
Thanks,
Bob
>sorry about the BooBoo with the map I had the html doc saying load a jpg
>instead of a gif image
> It"s all go now
>
> Dave
>At 09:21 PM 4/26/97 -0600, you wrote:
>>Dave-
>>> at the top of my quakes page is a relief map showing the recent
>>> events in the hills nth of the San Fernando Valley
>>>
>>> http://psn.quake.net/dave/quakes.htm
----- earthquake WARNING research -----
--- animals, people, scientific evidence ---
--- http://www.teleport.com/~bfryer ---
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: S. Cal. list updated
Date: Sun, 27 Apr 1997 21:28:29 +1200
Thanks Ray
I e-mailed WA6SUL a personal note to that effect
commenting that I was only passing on info that, maybe, not all were aware
of..... and commenting to him that if he wanted to pubically flame me he
could have at least has signed his name.
I'm sure none of us want this excellent medium for information xfer to
degenerate
TNX for you thoughts SUBJECT CLOSED
Dave
At 12:03 AM 4/27/97 -0700, you wrote:
>wa6sul,
>
>I am sorry, but I think it is so very obvious to everyone where Dave obtain
>the updated S. Cal list and I cannot understand how you thought he was
>trying to infer he was the source of the information/data??? His post/note
>did not come across that way to me at all and I appreciated him posting the
>updated list.
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Dennis Leatart <ASTROSEEK@.........>
Subject: WE GOT HIT AGAIN!!!!!!!!
Date: Sun, 27 Apr 1997 04:18:15 -0700
Almost same time-- same station. Felt like an instant replay!!
--
_____ __
| \.-----.-----.-----.|__|.-----.
| -- | -__| | || ||__ --|
|_____/|_____|__|__|__|__||__||_____|
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: WE GOT HIT AGAIN!!!!!!!!
Date: Mon, 28 Apr 1997 00:00:46 +1200
dennis,
Stop....!!
you are making me so envious
Dave
At 04:18 AM 4/27/97 -0700, you wrote:
>Almost same time-- same station. Felt like an instant replay!!
>--
> _____ __
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: WE GOT HIT AGAIN!!!!!!!!
Date: Mon, 28 Apr 1997 00:08:19 +1200
At 04:18 AM 4/27/97 -0700, you wrote:
>Almost same time-- same station. Felt like an instant replay!!
>--
Just downloaded the seismo cam image you are correct the seismogram is
almost identical in amplitude and duration
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
http:/www.es.co.nz/~dann/home.html ( New Zealand access only )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "The Allen Family" <frallen@.......>
Subject: Re: 1990 PSN proposal (Re: We got hit by a big one!!!)
Date: Mon, 28 Apr 1997 09:59:24 -0400
Mr Cranswick
I enjoyed the article about a 'people's ' system. I lurk in the
background reading all the neat stuf going by. My first and only
seismograph was built in the mid 80's, was assemble language, 6802, had a 8
bit A-D, and caused me to be banned from every lab at work. I understand
roll paper for the chart machines usage went up a bit. <grin>
What I never see addressed, for those of us with computer expertise, and
little machining equipment, is a package for the hardware. If someone would
put a price on a hardware side of a long or short period system, I think
there would be a lot of readers who would come out of the woodwork.
If you are emailing more information , I would appreciate being on the
receiving end.
Thanks.
----
From: Edward Cranswick <cranswick@........>
To: PSN-L Mailing List <psn-l@.............>
Cc: rcbaker@........
Date: Saturday, April 26, 1997 10:08 PM
Subject: 1990 PSN proposal (Re: We got hit by a big one!!!)
>Roger-
> Your post about:
>
>> up with a $20 instrument that you can scatter around like jellybeans
> [see full message below]
>
>reminds me of my wet dreams on the subject, "Proposal for a People's
>Seismograph Array...", which we presented at the American Geophysical
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jeff Batten <batten@...............>
Subject: Re: 1990 PSN proposal (Re: We got hit by a big one!!!)
Date: Sun, 27 Apr 1997 09:35:07 -0700
>Mr Cranswick
>I enjoyed the article about a 'people's ' system. I lurk in the
>background reading all the neat stuf going by. My first and only
>seismograph was built in the mid 80's, was assemble language, 6802, had a 8
>bit A-D, and caused me to be banned from every lab at work. I understand
>roll paper for the chart machines usage went up a bit. <grin>
>What I never see addressed, for those of us with computer expertise, and
>little machining equipment, is a package for the hardware. If someone would
>put a price on a hardware side of a long or short period system, I think
>there would be a lot of readers who would come out of the woodwork.
I am currently selling a vertical seismometer for $300. It has a period of
approximately 8-10 seconds. You can check out some of the quakes it has
recorded at http://www. primenet.com/~seismo.
As for quakes, for the last two nights we have been awakened by two really
scary ones here in L.A. A 5.0 and a 4.9. Having rode out the Northridge
quake at 5km with over 1.5g, I do not like to experience them close up. I
hope they stop ASAP.
Jeff
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: wcatino@.............
Subject: Roger Baker - science guy!
Date: Sat, 26 Apr 97 08:33:02
Roger,
You forgot to leave your email address on your instrumentation letter!
walt (wcatino@..............
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "wa6sul" <wa6sul@.............>
Subject: Re: S. Cal. list updated
Date: Mon, 28 Apr 1997 23:26:21 -0700
Thanks Ray for the great Isaiah site. I have been looking for this for some
time.
Sorry, David got so irate about my message. My point was not to flame him
at all. I was trying to make the point that putting the source of
imformation is helpful to all, particularly the newbies (future
seismologists) who may be reading the board. They would not necessarily
know where all the info originates from without a citation.
It onlly takes a few keystrokes, and the oldtimers would ignore the known
citations.
The new members do appreciate new info sites.
Again thanks for the ISAIAH site info.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Charles R. Patton" <patton@..........>
Subject: Re: seismometer/gravimeter
Date: Tue, 29 Apr 1997 10:17:44 -0700
Roger, you wrote:
A magnet is adjustably mounted nearby so that it very nearly
balances the weight of the free end and relatively heavy of the
filament, greatly magnifying the force of gravity. The lens is
actually the tip of the filament fused into a glass bead. This
free end swings up and down past a light emitter and detector
behind little slits in aluminum foil. Therefore only a few mi-
crons of vertical motion are easily registered with a
circuit ....
I followed this and subsequent posts with great interest. I
especially liked the micromanometer. I do have one comment about
the above though. When Vince Migliore was publishing Geo-
Monitor, he had several contributions from Ray Cole and Ken
Cornell concerning magnetic field strength detectors. This was
in conjunction with experiments to monitor electromagnetic fields
as possible pre-cursors to seismic activity. One of the last
versions of a detector was a long arm, off-center, on an edge
pivot whose weight was counter-balanced by opposed magnets. Ken
added a coil/oscillator structure which, in addition to providing
a method of position measurement, caused the arm to continually
rock, eliminating the hysteresis problem. Several people built
variations of this instrument and saw changes at different times.
My point is that by using a magnetic field as a very good spring,
you also open yourself up to measuring variations in the local
geomagnetic field also as that would change the effective "rate"
of the "spring". So did you magnetically shield or otherwise do
some tricks to try to null or eliminate this potential source of
error?
Charles R. Patton, Editor, Geo-Monitor
patton@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Citations
Date: Tue, 29 Apr 1997 09:28:18 -0800
Hello ?,
I think you made a good point about citations. One problem
with Email is that in the absence of body language and voice
inflections, multiple interpretations of tone are possible.
One thing that would help is including your name and location.
That adds a friendly tone to the message.
Just a suggestion :-)
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jeff Batten <batten@...............>
Subject: Mercury Pendulm Seismometer
Date: Tue, 29 Apr 1997 10:57:09 -0700
A good article-
A Mercury Pendulm Seismometer
William W. Gile
Geophys. J. R. astr. soc (1974) 36, 153-165
Jeff Batten - Research Engineer
Caltech Seismo Lab
1200 E. California Bl.
Pasadena, Ca.
91125
818-395-6965
Fax-818-564-0715
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Steve Hammond <shammond@..........>
Subject: Re: 1990 PSN proposal (Re: We got hit by a big one!!!)
Date: Tue, 29 Apr 1997 12:28:28 -0700 (PDT)
Ed, I still think you have a good idea that will work. When I finish
school in a few months, I expect to go back to work on this proposal. I
had to write a paper for a class about fuzzy logic and ended up writing a
spec for the shoe box seismograph. Like I said, in a few months...
Regards,
Steve Hammond Public Seismic Network San Jose, California
On Sat, 26 Apr 1997, Edward Cranswick wrote:
> Roger-
> Your post about:
>
> > up with a $20 instrument that you can scatter around like jellybeans
> [see full message below]
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
> A Proposal for a People's Seismograph Array Based on Home Computers in
> the San Francisco Bay Area
>
> E. Cranswick
> R. Banfill
> > means. The implication of this, I suppose, is that somebody should come
> > up with a $20 instrument that you can scatter around like jellybeans and
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: bfryer@............ (Bob Fryer)
Subject: SCAM ? - SIMI VALLEY, Newhall, Castaic
Date: Tue, 29 Apr 1997 15:41:02 -0700 (PDT)
Information SCAM or a swarm ??
Most of the SIMI VALLEY, Newhall, Castaic events occurred in an area about
3 miles in diameter. Is this a human, computer, or a communications
problem?
Note that all three 'locations' used the same coordinates: **34.38N 118.66W
97/04/26 10:37:30 34.37N 118.67W 15.5 5.0MLG A 7 mi. NNE of SIMI VALLEY
97/04/26 10:40:29 34.37N 118.67W 14.5 4.0MLG A 7 mi. NNE of SIMI VALLEY
97/04/26 10:53:42 34.37N 118.67W 19.0 2.4MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 11:16:43 34.38N 118.68W 17.0 2.1MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 11:55:47 34.38N 118.67W 14.5 3.8MLG A 8 mi. NNE of SIMI VALLEY
97/04/26 12:01:56 34.38N 118.67W 17.1 2.4MLG A* 8 mi. NNE of SIMI VALLEY
97/04/26 12:21:24 34.38N 118.67W 15.8 2.6MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 12:29:26 34.37N 118.67W 19.7 2.2MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 13:02:38 34.36N 118.68W 17.9 2.4MLG A* 6 mi. NNE of SIMI VALLEY
97/04/26 13:08:59 34.37N 118.67W 17.8 2.3MLG A* 7 mi. NNE of SIMI VALLEY
97/04/26 15:51:11 34.38N 118.67W 15.5 2.4MLG A* 8 mi. NNE of SIMI VALLEY
97/04/26 16:13:42 34.37N 118.67W 14.6 3.4MLG A 7 mi. NNE of SIMI VALLEY
97/04/26 16:59:15 34.38N 118.67W 15.6 2.0MGN A* 8 mi. NNE of SIMI VALLEY
97/04/27 08:04:58 34.39N 118.67W 19.5 2.2MLG A* 8 mi. NNE of SIMI VALLEY
97/04/27 11:33:50 34.37N 118.70W 18.7 2.5MLG B* 6 mi. NNE of SIMI VALLEY
97/04/27 12:14:05 34.38N 118.66W 14.8 2.2MLG A* 8 mi NNE of SIMI VALLEY**
97/04/27 12:37:47 34.38N 118.66W 15.9 2.0MLG A* 8 mi NNE of SIMI VALLEY**
97/04/27 17:55:21 34.36N 118.70W 21.0 2.1MLG A* 6 mi. NNE of SIMI VALLEY
97/04/28 23:04:44 34.37N 118.69W 21.1 2.2MLG A 7 mi. NNE of SIMI VALLEY
97/04/29 05:00:52 34.38N 118.68W 13.7 2.1MLG A 7 mi. NNE of SIMI VALLEY
97/04/26 10:54:30 34.39N 118.65W 11.5 3.2MLG A 7 mi. W of NEWHALL
97/04/26 10:57:55 34.37N 118.66W 18.9 2.6MLG A* 7 mi. W of NEWHALL
97/04/26 11:10:04 34.38N 118.65W 11.9 3.2MLG A 7 mi. W of NEWHALL
97/04/26 11:33:37 34.38N 118.65W 12.8 3.2MLG A 7 mi. W of NEWHALL
97/04/26 12:31:13 34.38N 118.65W 15.1 2.6MLG A* 7 mi. W of NEWHALL
97/04/26 14:31:34 34.38N 118.65W 13.2 3.0MLG A 7 mi. W of NEWHALL
97/04/27 11:09:28 34.38N 118.64W 14.4 4.9MLG A 6 mi. W of NEWHALL
97/04/27 11:13:16 34.38N 118.64W 15.0 2.6MLG A* 6 mi. W of NEWHALL
97/04/27 11:20:36 34.38N 118.65W 21.3 2.3MLG B* 7 mi. W of NEWHALL
97/04/27 11:22:39 34.39N 118.65W 13.9 2.5MLG A* 6 mi. W of NEWHALL
97/04/27 11:30:15 34.38N 118.64W 14.4 2.3MLG A* 6 mi. W of NEWHALL
97/04/27 11:31:21 34.38N 118.64W 10.6 3.6MLG A 6 mi. W of NEWHALL
97/04/27 11:31:51 34.38N 118.65W 11.1 3.4MLG A 7 mi. W of NEWHALL
97/04/27 12:14:57 34.38N 118.65W 19.5 2.1MLG A* 7 mi. W of NEWHALL
97/04/27 12:18:53 34.38N 118.64W 13.2 2.7MLG A* 6 mi. W of NEWHALL
97/04/27 12:25:26 34.38N 118.65W 17.7 2.2MLG A* 6 mi. W of NEWHALL
97/04/27 15:16:48 34.38N 118.62W 15.8 2.0MLG A* 5 mi. W of NEWHALL
97/04/27 15:18:35 34.38N 118.63W 14.1 3.3MLG A 6 mi. W of NEWHALL
97/04/27 19:36:45 34.38N 118.65W 18.8 2.3MLG A* 7 mi. W of NEWHALL
97/04/28 15:25:44 34.38N 118.66W 14.4 2.4MLG A 7 mi. W of NEWHALL**
97/04/26 11:08:55 34.39N 118.66W 13.3 2.6MLG A* 8 mi. SSW of CASTAIC
97/04/26 11:16:18 34.38N 118.66W 13.8 2.6MLG A* 8 mi. SSW of CASTAIC**
97/04/27 11:37:35 34.39N 118.66W 13.4 2.5MLG B* 8 mi. SSW of CASTAIC
97/04/27 12:22:50 34.39N 118.66W 12.2 2.5MLG A* 8 mi. SSW of CASTAIC
97/04/27 12:44:05 34.39N 118.66W 11.5 2.3MLG A* 8 mi. SSW of CASTAIC
97/04/27 21:34:28 34.39N 118.66W 14.9 2.7MLG A* 8 mi. SSW of CASTAIC
97/04/27 21:44:47 34.39N 118.66W 15.3 2.6MLG A* 8 mi. SSW of CASTAIC
97/04/28 01:20:38 34.39N 118.65W 12.0 3.0MLG A 8 mi. SSW of CASTAIC
List from:
[scec.gps.caltech.edu]
Login name: quake In real life: SCSN Data Access
Directory: /export/scec/user1/quake Shell: /usr/local/bin/tcsh
Take care,
Bob
----- earthquake WARNING research -----
--- animals, people, scientific evidence ---
--- http://www.teleport.com/~bfryer ---
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From: roger baker <rcbaker@........>
Subject: Toward a jellybean seismometer
Date: Tue, 29 Apr 1997 18:16:03 -0500 (CDT)
Friends,
Here is what Ive learned recently as the result of a
self-initiated crash course. I am not an expert but have reviewed the
literature and will cite a few experts and then throw in some educated
opinions of my own. This is an effort to explain what appear to me to be
some considerations for amateurs wishing to build small cheap
seismographic instruments with useful sensitivity. My goal is to try to
understand any design options that have been neglected or ignored for
whatever reason.
As a relative novice Im probably wrong on a few points. If so, I welcome
criticism and comment from the real pros out there. This is not a paper
submitted for publication but a draft essay submitted for comment.
That said, I have been considerably impressed by how much the state of
the art has increased since the 1940s and how nearly some relatively
small instruments now seem to approach certain theoretical performance
limits except for cost. Melton has provided a list of eight useful
principles for practical seismometer design in his excellent review
article (4; p 113-114).
Some of the biggest questions regarding optimum amateur design principles
seem to me to be the choice of a suspension and the optimum size of the
pendulum mass of a small instrument.
....A small vertical seismometer whose inertial mass is supported by a
leaf spring has been developed as a replacement for conventional
long-period (LP) seismometers. The mechanical sensor has a virtually
infinite natural period and is operated in a force-balance feedback
configuration with an overall response identical to that of a 20-sec LP
seismometer. Main considerations in the design were economic production
and efficient shielding against environmental disturbances. The sensor is
thermally coupled to the ground and protected from atmospheric pressure
variations by a bell jar. This allows increasing the useful gain at very
long periods by two orders of magnitude compared to a standard LP
seismograph. The instruments resolve ground noise at least from a 0.3 to
300-sec period (typically from 0.1 to 3000 sec) and have a dynamic range
of 140 dB... (7; p 2349).
Since temperature is one of the great universal enemies of stability and
accuracy for most instruments, one would normally tend to favor small
designs that can be surrounded by thermostatted metal enclosures
maintained a few degrees above ambient, perhaps even inserted into a
thermos bottle.
Rigid instrument mountings are probably one important consideration, but
this factor has not been much emphasized in the literature. One of the
easiest ways to calibrate the steady state sensitivity of an instrument
is by tilting it slightly. The most favored locations for seismometers
are on concrete piers or inside mines or in concrete enclosures, or best
of all in deep bore holes (5; p 724-5). Interestingly , one
sophisticated consideration is that deep bore hole sites are not so
subject to local atmospheric pressure cells, which are actually reported
by Sorrels to distort the surface of the earth enough to cause slight
seismograph inaccuracies due to tilt (4; p 95).
Temperature, barometric pressure and external magnet fields all
significantly affect the response of sensitive instruments. In general
the use of force feedback seems to be well established as a useful way to
make a small mass instrument response relatively insensitive to its own
natural period. In this context, the use of an external reversible
solenoid to generate a magnetic feedback force on a small iron mass seems
like a good option for amateur design. I had imagined the external
magnetic field from the earth, etc., is likely to be relatively small and
constant compared to the force feedback magnetic field induced on an iron
pendulum mass by the solenoid coils. The same argument would apply to my
proposed magnetic suspension that supports most of the weight of an iron
inertial mass. A small instrument could always be encased in a permalloy
canister to minimize external magnetic influences.
To detect the changed position of the pendulum mass due to seismic
disturbances, two leading options are optical and capacitative
detection, since both tend to create little back force, are cheap and
easy to build, and both work well with very small masses. The more
sensitive of the two detection options for detecting very small
displacements is a capacitive bridge, for a vertical axis instrument
using two external horizontal plates straddling a third horizontal plate
mounted to the pendulum mass.
This would mean that a glass or quartz support fiber spring must be
conductive, but it is easily possible to fire conductive but very thin
bright gold coatings sold for ceramic decoration onto glass. A sensitive
capacitative micrometer built with easily available parts and using
lock-in detection is said to detect a displacement of 10 to the minus
11th mm over short periods of time (2; p 589), whereas, from what I
gather, an optical displacement detector could probably do no better
than about 10 nanometers, thus being less sensitive to displacement by a
factor of about 100,000. It is said that the AC signal should be kept to
a volt or less to prevent electrostatic forces from becoming significant.
Horizontal axis displacement instruments with force feedback could be
nothing more than an iron weight or magnet suspended from one (or two to
restrict the axis of movement) quartz fibers. Quartz fibers that appear
to be useful for such purposes are relatively cheap in our era of fiber
optics. These can easily be bent or pulled thinner, if not very
succesfully fused, with a propane handtorch flame. Quartz is the reigning
champion high class standard for instrument design, but I know of no good
reason that Pyrex (or even soft glass) should be inferior for support
design purposes except for their inferior coefficients of expansion.
Such filament supports can be used together with fine coils to restore
the position of the magnetic mass. For vertical axis instruments, it has
been a common practice to use a number of fairly sophisticated suspension
systems such as the La Coste zero length spring to extend the natural
period. Nevertheless, simpler suspensions seem to be adequate when the
travel of the inerial mass is restricted towards zero motion by force
balancing. For example, masses extending from horizontal torsion
filaments seem to work well for this, as do various simple leaf spring
arrangements (1, 7).
As previously indicated, I believe the option of a horizontal glass or
quartz filament with an attached iron mass whose weight is very nearly
balanced with a large magnetic field magnet is one attractive design
option that may have been ignored by most designers. For example, if 99%
of the weight of an iron mass can be supported by an external field, then
the end result is equivalent to this same mass supported by an uncommonly
weak spring, thus permitting the natural period to be lengthened and
sensitivity to small changes in the residual force to be increased.
However it is not clear that this novel suspension would be needed if a
very sensitive capacitance detector and force feedback were used to full
advantage. I also understand that the field strength of ceramic magnets
may vary appreciably with temperature, making it important to control the
temperature of this field magnet along with the rest of the seismometer.
Temperature control is probably important in any case.
One of the most valuable insights that I have gotten from a review of the
literature is that the main reason large masses have traditionally used
for seismometers is that if the energy imparted by a slow seismic
disturbance is very small, a large mass can store up more kinetic energy
for detection, whereas the use of force feedback and the elimination of
air resistance can largely eliminate this requirement. However, the use
of a small mass implies that the spring and mass combination must have a
high Q (the system must be able to maintain oscillations at its natural
frequency for a long time) to be able to detect the same disturbance.
....if the mass is very small, the absolute damping must be very
low--effectively the Q must be very high... (3; p 506)...The realization
that the thermal noise of a seismometer depended on its damping losses
(rather than on its mass) suggested that a much lower mass and smaller
seismometer could be devised, provided that amplifiers could compensate
for reduced seismometer oputputs. Briefly stated, the thermal noise
(force) of a periodic system, electrical or mechanical resides in its
lossy elements. The system oscillations indicate the presence of some
force, including thermal noise, but the amplitude of mass (or spring)
oscillation is only a measure of energy, not the energy source
itself...(3; p 509).
Perhaps another way to put this is that if the natural period of the
spring and mass combination is short compared to the period of
disturbance to be detected, it is possible provided that the energy being
added to the system is not dissipated during this interval of kinetic
energy accumulation by air resistance and the like.
It has also been stated by Melton, who is was (and perhaps still is) on
the leading edge of seismometer design, that masses on the order of 100
grams or more are needed for good practical sensitivity. However, Block
seems to have been the first to use a mass as small as 10 grams
cantilevered on a quartz fiber with good results (1). A large part of the
justification for 100 grams seems to be that air tends to damp the spring
and mass combination too much with smaller masses. So why not enclose the
instrument in a vacuum where there is little air damping and masses
mounted on quartz suspensions could have a very high Q? Melton argues,
interestingly, that a sufficiently good vacuum cannot be maintained
within a seismometer due to contamination due to organic matter.
....In any seismometer having a mass of less than 100 g, air damping at
atmospheric pressure may become significant, and power disipated thereby
is not available to an amplifier. If the seismometer case is evacuated to
reduce this loss, the vacuum obtained must be good enough to make the
mean free path of the remaining gas or vapor molecules large with respect
to the average cross section dimensions of elements moving with respect
to one another. This is not a well defined value, but experience shows
that such vacuums are not easily maintained in the presence of organic
materials... (4; p 113).
However, this raises the interesting question of whether a small quartz
or Pyrex filament and iron mass seismometer with capacitative detection
plates could not be hermetically sealed within a test tube-like enclosure
under high vacuum. Perhaps surrounding the active elements with dry
helium or hydrogen could also provide some benefit.
It is sometimes pointed out that Brownian motion of the seismometer mass
sets a fundamental limit on the sensitivity of the seismometer, and that
this limit is frequency dependent (7; p 2357). A similar theory was first
worked out by Hardy and others to explain the theoretical resolution
limits of small galvanometer mirrors on torsion fiber suspensions. While
it is true that there are such sources of quantum noise that limit the
ultimate sensitivity of all scientific instruments, it seems that this
theoretical limit to the inertial mass is not nearly so likely to be
limiting in practice for the frequencies of seismic disturbances compared
to the reduced Q of the system due to air resistance. One should note
that the Worden gravimeter achieves a very high long period sensitivity,
making it a very sensitive tidal gravimeter for example, but yet the
total mass of the quartz suspension and sensing mass together is less
than one gram.
Clearly, a long-range trend of seismometer instrumentation since the
1940s has been to reduce the size of the spring and mass combinations
that comprise the physical basis for all seismometry: ...Conventional
seismometers employ masses of several kilograms suspended with periods of
several seconds, but it is possible to achieve the same detection
capability with much smaller masses suspended at shorter periods. Such
instruments are valuable for borehole applications or where many
instruments must be rapidly set up... A force feedback system maintains
the mass stationary with respect to the instrument frame and the
instruments have a response defined by feedback from DC to to 10 Hz. A
single minaiture instrument can thus provide data over the whole of the
seismic range... (6, p 605).
Small seismometers with uncommonly small masses, and which might be
relatively cheap to build, and very small instruments with a vacuum
enclosure, therefore appear to be a fertile ground for amateur
experimentation. Small instruments could have other advantages such as
better temperature control. The question remains how far the trend toward
small detection masses can continue until it becomes more trouble than it
is worth or reduces practical sensitivity. There is no probably no need
to increase instrumental sensitivity past the point that micro seismic
background noise, from ocean waves and the like, dominates the data in
those frequency bands.
Another issue is what sensitivities are desirable at low frequencies
longer than about ten seconds. These very low frequencies are associated
with the important major earthquake tremors that refract from deep layers
and even travel through the center of the earth.
References:
(1) Block B. and Moore R.D. (1970). Tidal to seismic frequency
investigations with a quartz accelerometer of new geometry, J. Geophys.
Res., 75, p 1493-1505.
(2) Jones R.V. and Richards J.C.S.,(1973), Design and applications of
sensitive capacitance micrometers, J.Phys. E., 6, p 589-600.
(3) Melton B., (1981). Earthquake seismograph development: A modern
history--Part 1, EOS, 62, p 505-510.
(4) Melton B., (1976). The sensitivity and dynamic range of inertial
seismographs, Rev. Geophys. and Space Physics, 14, p 93-116.
(5) Melton B. and Kirkpatrick B. M., (1970) The symmetrical triaxial
seismometer--its design for application to long period seismometry, Bull.
Seism. Soc. Am., 60, p 717-739.
(6) Usher M.J., Guralp C., and Burch R.F. (1978). The design of miniature
wideband seismometers, Geophys. J.,55, p 605-613.
(7) Wielandt E. and Streckeisen G. (1982). The leaf-spring seismometer
design and performance, Bull. Seism. Soc. Am., 72, p 2340-2367.
--Yours, Roger Baker; Science Hacker, April 29, 1997
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Public Seismic Network Mailing List (PSN-L)
From: David Josephson <david@...............>
Subject: Re: Toward a jellybean seismometer
Date: Tue, 29 Apr 1997 16:42:16 -0700 (PDT)
A couple of random comments to fill in your fascinating survey of
state-of-the-art. The mass on a quartz spring design describes the Worden
gravimeter fairly closely; this has been in use for 50 years and various
methods (principally optical) are used to sense the position of the mass.
You've also come close to describing the superconducting gravimeter in
which a hollow sphere of superconducting material is levitated in a
magnetic field and its position sensed capacitatively. These have been
produced in small quantities by GWR in San Diego. In both cases, these
devices have response to DC and are used at fixed locations principally to
detect gravity anomalies, earth tides, etc. and are also used in moving
platforms to map gravity as a geophysical mapping and exploration tool. If
you expand your search to include gravimeters I think you'll find another
bunch of interesting designs to examine.
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Public Seismic Network Mailing List (PSN-L)
From: Robert Avakian <ravakian@............>
Subject: Re: jelly bean seismology
Date: Tue, 29 Apr 1997 15:15:27 -0700
Edward Cranswick wrote:
>
> Roger-
> Your post about:
>
> > up with a $20 instrument that you can scatter around like jellybeans
> [see full message below]
>
> reminds me of my wet dreams on the subject, "Proposal for a People's
> Seismograph Array...", which we presented at the American Geophysical
> Union Meeting at San Francisco in December 1990, a year after the Loma
> Prieta Earthquake. Unbeknownst to me at the time I wrote the abstract,
> Steve Hammond and others of what became the PSN San Jose, were already
> doing much of what we proposed. However, the cheap, mass-distributed
> seismograph is still virtual. Send me your snail-mail address, and I'll
> send you some more hardcopy on the subject.
> -Edward
>
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
> A Proposal for a People's Seismograph Array Based on Home Computers in
> the San Francisco Bay Area
>
> E. Cranswick
> R. Banfill
>
> The widespread use of microcomputers by private citizens and the recent
> public awareness of seismic hazard following the Loma Prieta Earthquake
> suggest a new method of monitoring seismological phenomena in the San
> Francisco Bay Area. It is technically feasible to build a
> self-contained digital seismic data acquisition unit (SDAU) that would
> utilize the modem of a home computer (Macintosh or IBM-PC-compatible*)
> to communicate seismic information to a central processing/archival
> system (CPAS) minicomputer located at the U. S. Geological Survey in
> Menlo Park, California. There are approximately 100,000 home
> microcomputers within a 100 km radius of Menlo Park. If 1% of these
> users were to participate in the program described here, and if half of
> those regularly generated reliable data, the resulting array would have
> an average inter-station spacing of ~8 km. The SDAU would digitize
> seismic signals from a 3-component FBA sensor buried immediately outside
> the residence and scan these timeseries in realtime for seismic events
> which, when detected, would be stored in RAM. A post-processor would
> analyze the event timeseries for P- and S-wave phase times, peak
> amplitudes, durations, etc., and these event parameters would be
> routinely transmitted by the host microcomputer to the CPAS via
> telephone. The CPAS, similar to a telephone switching/accounting
> computer system, would be equipped with at least 100 input lines and
> would maintain an archive of all user calls, i.e., a history of each
> station. A clock correction to the internal clock of each SDAU would be
> recorded by the CPAS whenever the host microcomputer uploaded event
> parameters. Crucial to the success of the proposed data acquisition
> scheme would be an effective USGS/SDAU-users group. The users group
> would provide software/hardware support and publish a monthly newsletter
> which would summarize the results of the array's operation and give
> recognition to users distinquished by the completeness and reliabilty of
> their data. The integrity of the dataset would be maintained by its
> redundancy and by its current and comprehensive station history. The
> high spatial density of stations would permit the use of simple methods
> of analysis, e.g., tomography and spectral amplitude ratios, and provide
> a set of seismic observations which approached the scale of geologic
> observations. In an age of government budget deficits, popularity of
> High-Tech, and public recognition of the inevitability of earthquakes,
> the proposed scheme could provide a similtaneous view of the seismic
> source process and the micro-regional site response which is
> increasingly critical to life in the San Francisco Bay Area.
>
> * Use of tradenames is for descriptive purposes only and does not imply
> an endorsement by the U. S. Geological Survey.
>
> (Cranswick, E., and Banfill, R., 1990, Proposal for a high-density
> people's seismograph array based on home computers in the San Francisco
> Bay Area: Eos (American Geophysical Union, Transactions), v. 71, no.
> 43, p. 1469.)
>
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
> roger baker wrote:
> >
> > Friends,
> > It is starting to occur to me that any idiot can build a pretty
> > sensitive seismometer, but nobody can quite figure out what the data
> > means. The implication of this, I suppose, is that somebody should come
> > up with a $20 instrument that you can scatter around like jellybeans and
> > link them up with a computer network. At this point everything turns into
> > mathematics, which I'm terrible at. But I think I might be pretty good at
> > designing the jellybeans.
> > The really interesting question to me right now is if you design a
> > range of sizes of seismometers using the force feedback principle, is
> > there any practical loss of sensitivity when you make them very small?
> >
> > For example, could you build arrays of accelerometers on silicon chips that
> > would be as sensitive as the massive old instruments? If not, exactly what
> > physical laws stand in the way? It seems like very small sensing masses
> > mounted on quartz fibers or their equivalent, the use of active force
> > balancing, and capacitive displacement sensing is the way to go. So what
> > prevents you from designing a chip or at least a pocket sized instrument
> > that could do the job of the old monsters? As you know, you can increase
> > the sensitivity of any sensor by two by building four identical sensors
> > and averaging their responses, or by ten by building 100, etc. This is
> > the way the ear gets its sensitivity I think--by having lots of sensing
> > hairs in parallel. But notice that the motion sensing hairs in the ear are
> > all different lengths, as well as being the most sensitive microphone known.
> > By analogy, if you could build very small cheap accelerometers,
> > or micro-seismometers, you would probably try to build them tuned to
> > many different frequencies to maximize their inherent sensitivities. If
> > you use the force feedback principle, is damping still helpful, or would
> > you rather enclose the micropendulum in a vacuum, as I suspect?
> >
> > --Yours, Roger
> >
> > _____________________________________________________________________
> >
> > Public Seismic Network Mailing List (PSN-L)
> >
> > To leave this list email listserver@............. with the body of the
> > message: leave PSN-L
>
> --
> Edward Cranswick Tel: 303-273-8609
> US Geological Survey, MS 966 Fax: 303-273-8600
> 1711 Illinois St cranswick@........
> Golden, CO 80401 USA E.M. Forster said, "Only connect".
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
Back in the dark days of the Viet Nam "exercise" I was told about a
seismometer encased in a slim steel dart that was used to monitor
traffic and troop movement on the Ho Chi Minh Trail. Air dropped near
the trail, it picked up the vibrations of passing troops and vehicles
and broadcast to surveilence aircraft overhead. I never saw one, but if
the description I was given is true, the sensors had to be small, self
powered, and as rugged as a cermaic privy. The darts were dropped from
a fair height and designed to penetrate the forest cover and soil to a
reasonable depth. Possible source for a rugged, cheap and remote
seismogarph?
Does anyone out there know any more about these devices?
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Public Seismic Network Mailing List (PSN-L)
From: David Josephson <david@...............>
Subject: Re: jelly bean seismology
Date: Tue, 29 Apr 1997 23:20:33 -0700 (PDT)
On Tue, 29 Apr 1997, Robert Avakian wrote:
> Back in the dark days of the Viet Nam "exercise" I was told about a
> seismometer encased in a slim steel dart that was used to monitor
> traffic and troop movement on the Ho Chi Minh Trail. Air dropped near
> the trail, it picked up the vibrations of passing troops and vehicles
> and broadcast to surveilence aircraft overhead. I never saw one, but if
> the description I was given is true, the sensors had to be small, self
> powered, and as rugged as a cermaic privy. The darts were dropped from
> a fair height and designed to penetrate the forest cover and soil to a
> reasonable depth. Possible source for a rugged, cheap and remote
> seismogarph?
Not really. There are quite a few of these around in several variants,
the sensing element of the most sensitive one is a generic 30 to 40 Hz
vertical geophone similar to those used in shallow reflection seismic
surveys. Fair Radio Sales in Lima, OH probably still has some. The
cutoff frequency is too high, and the electronics is simply a
threshhold detector that sends a coded beep once the threshhold is
exceeded. Now there may be more advanced ones but I'd expect them all
to be sensitive in the 10-100 Hz range rather than lower.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: jelly bean seismology
Date: Wed, 30 Apr 1997 20:19:54 +1200
David
As I recently wrote on this forum I porchased 4.5 Hz geophones
from Geo Space Corp.
in Texas at US$60.00 these are very effective units for small local or
larger quakes up to 1000 km at that price you cannot go wrong they are
very small in size ( 3cm dia and 3.5 cm high) so are very easily deployed.
I have been using this style of short period seismometer for a good
number of years with great success
There in a nutshell is your problem solved........ you can stick
on whatever recording sys. you like.
Dave N.
At 11:20 PM 4/29/97 -0700, you wrote:
>On Tue, 29 Apr 1997, David Josephson wrote:
>Not really. There are quite a few of these around in several variants,
>the sensing element of the most sensitive one is a generic 30 to 40 Hz
>vertical geophone similar to those used in shallow reflection seismic
>surveys. Fair Radio Sales in Lima, OH probably still has some. The
>cutoff frequency is too high, and the electronics is simply a
>threshhold detector that sends a coded beep once the threshhold is
>exceeded. Now there may be more advanced ones but I'd expect them all
>to be sensitive in the 10-100 Hz range rather than lower.
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Dudley Warner <dudley@..............>
Subject: Re: jelly bean seismology
Date: Wed, 30 Apr 1997 10:08:23 -0700
David Josephson wrote:
>
> On Tue, 29 Apr 1997, Robert Avakian wrote:
>
> > Back in the dark days of the Viet Nam "exercise" I was told about a
> > seismometer encased in a slim steel dart that was used to monitor
> > traffic and troop movement on the Ho Chi Minh Trail. Air dropped near
> > the trail, it picked up the vibrations of passing troops and vehicles
> > and broadcast to surveilence aircraft overhead. I never saw one, but if
> > the description I was given is true, the sensors had to be small, self
> > powered, and as rugged as a cermaic privy. The darts were dropped from
> > a fair height and designed to penetrate the forest cover and soil to a
> > reasonable depth. Possible source for a rugged, cheap and remote
> > seismogarph?
>
> Not really. There are quite a few of these around in several variants,
> the sensing element of the most sensitive one is a generic 30 to 40 Hz
> vertical geophone similar to those used in shallow reflection seismic
> surveys. Fair Radio Sales in Lima, OH probably still has some. The
> cutoff frequency is too high, and the electronics is simply a
> threshhold detector that sends a coded beep once the threshhold is
> exceeded. Now there may be more advanced ones but I'd expect them all
> to be sensitive in the 10-100 Hz range rather than lower.
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
ESL here in the Bay Area worked on such a project which hid the
transducer and radio transmiter in "Rubber Rocks". These items were
dropped from the air around the DMZ to detect troop movements at night.
--
Dudley Warner National Semiconductor Corp., Integrated Processor
Group
(408)654-0969 dudley@.............. dudley221@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Magnetic declination
Date: 30 Apr 97 13:13:51 EDT
David Josephson,
Thanks for the URL to NOAA's GEOMAG program. I downloaded the PC version and
it runs fine.
A link in that to www.census.gov/cgi-bin/gazetteer (as your ref. to Tiger
noted) is also useful. It tries to give lat & lon and a lot of other info on
any town or zip code you name as well as links to census data on the town.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David Josephson <david@...............>
Subject: Re: jelly bean seismology
Date: Wed, 30 Apr 1997 12:23:43 -0700 (PDT)
On Wed, 30 Apr 1997, Dudley Warner wrote:
> David Josephson wrote:
> >
> > On Tue, 29 Apr 1997, Robert Avakian wrote:
> >
> > > Back in the dark days of the Viet Nam "exercise" I was told about a
> > > seismometer encased in a slim steel dart that was used to monitor
<snip)
>
> ESL here in the Bay Area worked on such a project which hid the
> transducer and radio transmiter in "Rubber Rocks". These items were
> dropped from the air around the DMZ to detect troop movements at night.
Are you sure you're supposed to say that? I had one of those, and one of
the plastic dog droppings too. There were also similar devices with
fluxgate magnetometers or search coils in them. With their primitive
analog telemetry it must have been fun for the elint guys to figure out
just which one was beeping. I think Dave Nelson's idea about regular civil
geophones which aren't expensive would work best.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: roger baker <rcbaker@........>
Subject: Re: jelly bean seismology
Date: Wed, 30 Apr 1997 15:41:47 -0500 (CDT)
Friends,
As Dave Nelson has pointed out, for short period waves, there is no point
in not buying a short-period geophone for $60. But for distant quakes,
long period is where the action is and that is where I think my
amateur design alternatives are likely to be useful. I didn't know about
force balancing until a week ago, but after my literature review I think
its an obvious choice for long period instruments. The various other
alternatives like the best inertial mass and the sensing and feedback and
vacuum enclosure options, etc., are more open to debate or discussion.
--Yours, Roger Baker
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Dennis Leatart <ASTROSEEK@.........>
Subject: Large Quake???
Date: Thu, 01 May 1997 05:23:20 -0700
Hi Everyone!!
I am picking up a large event that on first impression looks very
close-- but felt no motion here in Moorpark-- but the seismometer went
"full screen" for some time-- have seen no data on the web yet-- but
getting a good trace-- anyone else?? Time: 11:36 UT
--
_____ __
| \.-----.-----.-----.|__|.-----.
| -- | -__| | || ||__ --|
|_____/|_____|__|__|__|__||__||_____|
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Large Quake???
Date: Fri, 02 May 1997 01:18:24 +1200
nothing in New Zealand region Dennis this will be it.....
97/05/01 11:37:34 18.87N 107.26W 33.0 6.7Ms A OFF COAST OF JALISCO, MEXICO
Dave
At 05:23 AM 5/1/97 -0700, you wrote:
>Hi Everyone!!
>
>I am picking up a large event that on first impression looks very
>close-- but felt no motion here in Moorpark-- but the seismometer went
>"full screen" for some time-- have seen no data on the web yet-- but
>getting a good trace-- anyone else?? Time: 11:36 UT
>--
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: event
Date: Thu, 01 May 1997 05:57:06 -0700
Looks like Jalisco Mexico 6.7 @ 11:37:34 18.87N 107.26W. My pics are
off (small S wave magnitude).
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: event
Date: Fri, 02 May 1997 01:57:28 +1200
Yes i just played with your file in winquake changing the magit. factor
to 0.001 and putting the 'S' in the right spot gave the correct figures
Dave
At 05:57 AM 5/1/97 -0700, you wrote:
>Looks like Jalisco Mexico 6.7 @ 11:37:34 18.87N 107.26W. My pics are
>off (small S wave magnitude).
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jean-Jacques HUNSINGER <jjh@............>
Subject: Re: Large Quake???
Date: Thu, 01 May 1997 17:08:58 +0200
Dennis Leatart wrote:
>
> Hi Everyone!!
>
> I am picking up a large event that on first impression looks very
> close-- but felt no motion here in Moorpark-- but the seismometer went
> "full screen" for some time-- have seen no data on the web yet-- but
> getting a good trace-- anyone else?? Time: 11:36 UT
> --
hello,
I got the same at 12:12 UT here in France
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: jelly bean seismology (Recording Ground Motions Where People Live)
Date: Thu, 01 May 1997 09:29:25 -0600
PSN-
There has been such an outpouring of comments about "jelly bean
seismology" that I figured I'd put these two cents in before I leave the
office for the next week.
This is an article that was published in 1993:
Cranswick, E., Gardner, B., Banfill, R., and Hammond, S., 1993,
Recording ground motions where people live: Eos (American Geophysical
Union, Transactions), vol.74, no. 21, p. 243-244.
(it was originally entitled, "PUBLIC SEISMIC NETWORK AND SEDIMENTARY
BASINS: RECORDING GROUND MOTIONS WHERE THE PEOPLE LIVE", but space
limitations trimmed off the first phrase)
Much of the material about waveform telemetry is dated because BBSs have
been eclipsed by the Web, but the fundamental notion of deploying
low-cost, mass-produced seismometers in seismogenic regions with a
spatial density comparable to population density has yet to be realized.
I have not included the figure, but we will get that on a Website with
the article soon.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
RECORDING GROUND MOTIONS WHERE PEOPLE LIVE
E. Cranswick and B. Gardner (US Geological Survey, Golden, CO)
S. Hammond (Public Seismic Network, San Jose, CA)
R. Banfill (Small Systems Support, Big Water, UT)
Introduction
The 1989 Loma Prieta, California Earthquake caused spectacular damage to
structures 100 km away in the San Francisco Bay sedimentary basin -- the
Cypress Street viaduct overpass, the Bay Bridge and buildings in the San
Francisco Marina district. Although the few mainshock ground motions
recorded in the northern San Francisco Bay area were "significantly
larger ... than would be expected from the pre-existing dataset", none
were recorded at the sites of these damaged structures (Hanks and
Krawinkler, 1991). Loma Prieta aftershocks produced order-of-magnitude
variations of ground motions related to sedimentary basin response over
distances of 1-2 km and less (Cranswick et al., 1990). In densely
populated neighborhoods, these distances can encompass the residences of
thousands of people, but it is very unlikely that these neighborhoods
are monitored by even one seismograph. In the last decade, the
complexity of computer models used to simulate high-frequency ground
motions has increased by several orders of magnitude (e.g., Frankel and
Vidale, 1992), but the number of seismograph stations -- hence, the
spatial density of the sampling of ground motion data -- has remained
relatively unchanged. Seismologists must therefore infer the nature of
the ground motions in the great unknown regions between observation
points.
The strong response of sedimentary basins to seismic waves was largely
responsible for the damage produced by two devastating earthquakes in
the last decade: the 1985 Michoacan Earthquake which severely damaged
parts of Mexico City, and the 1988 Spitak Earthquake which destroyed
most of Leninakan, Armenia. Much of this response can be explained by
the conversion of seismic body-waves to surface waves at the
sediment/rock contacts of sedimentary basins (Bard et al., 1988). The
effectiveness of waveform conversion is a function of the angle of
incidence of the body waves and the geometry of the basin, and thus, the
ground motions are sensitive to the depth and direction of the source in
a fashion not predicted by one-dimensional, plane-layer models of
velocity structure (Papageorgio and Kim, 1991).
Seismographs are usually installed at good sites for observing seismic
sources, on rock characterized by low seismic noise. For site-response
research and to assess earthquake hazard, we need to deploy dense
seismograph arrays within the densely inhabited metropolitan areas built
on sedimentary basins. Such arrays would be prohibitively expensive if
implemented using traditional methods, but would be economical with new
approaches to the three requirements of data acquisition: 1) sites; 2)
instrumentation; 3) data management. The continuous operation of such
arrays would generate a database to constrain ground motion models and
begin to define the "site/source response."
A Modest Proposal
Cranswick and Banfill (1990) proposed the Public Seismic Network (PSN)
as a model for dense urban arrays. The PSN consists of event-triggered
digital seismographs owned and operated by private citizens. The
waveform timeseries recorded by each unit are automatically uploaded
over the owner's telephone to a data management center which monitors
and archives the data. The owner can also upload the timeseries to
his/her personal computer.
Permitting, installation and maintenance of seismographs represent
major costs of operating a network; utilizing station owner/operators
eliminates these costs. The owner/operator is also best able to deal
with problems of local cultural seismic noise and of vandalism, major
difficulties of operating seismographs in urban areas. There is no
substitute for a human being who regularly monitors the operation of a
piece of equipment, and there are many amateur seismologists and
interested citizens interested in and capable of doing so.
The network needs an inexpensive, reliable, standardized and
mass-produced seismograph: the digital seismological equivalent of a
Sony Walkman. It must be able to record three components of ground
acceleration with a dynamic range of 0.00001-1.0 g in the frequency band
0.1-20.0 Hz and maintain absolute time to a precision of 5 ms. Typical
records would be sampled at 50 sps/component and have a duration of
30-300 s. The unit must be constructed ruggedly enough and supplied
with sufficient data storage and a self-contained power source to
function as a strong motion recorder for several weeks of unattended
operation. The unit would make trivial the cost of data telemetry -- a
very large expense for most seismic networks -- by employing a 1200-baud
modem to transmit the compressed digital records over local telephone
lines to the data center. Using "state of the market" technology, we
estimate that 1,000 such units can profitably be manufactured and sold
for $500-1,000 apiece (see Nolet, 1993).
The data management center would be similar to the voicemail service
offered by phone companies: a telemetry, storage/retrieval system for
digitized waveforms. Most scientific databases do not dynamically
interact with the sources of the data, but the realtime credit
verification of a typical credit card system provides a model of how the
data center could maintain the integrity of a PSN network.
Amplitude/time calibrations, trigger/false-trigger counts, and ground
motion statistics of each seismograph could be automatically scrutinized
as regularly and rigorously as a credit card balance. Every time the
seismograph was triggered and called the data center to upload waveform
timeseries, a clock correction, corrected for telephone transmission
delay, would also be recorded. The seismograph would call the data
center at least once each day to be clock corrected and to transmit its
state of health, including a response calibration. Near-realtime
comparison of the records of adjacent seismographs would also monitor
instrument reliability. Based on its current and comprehensive history
of all seismographs, the data center could upload instructions to
seismographs that exhibited anomalous behavior to increase their
frequency of clock corrections, change their trigger parameters, perform
more exhaustive response calibration procedures, etc.
Both the credit card verification systems and telephone voice mail
systems now employed throughout the United States and many other
countries are able to dynamically maintain databases which are
simultaneously accessed in realtime over conventional telephone lines by
thousands of transmit/receive stations at rates of about 100,0000 phone
calls per day. Background seismicity would generate about 1,000
one-minute phone calls per day from a PSN system of a thousand
stations. The aftershock sequences of large local earthquakes could
exceed the ability of the data center to process all potential phone
calls in realtime, but the seismographs could store a hundred waveforms
internally and be programmed to prioritize waveform storage/transmission
according to some measure of event size. The data center would also
function as an electronic bulletin board system (BBS) for seismograph
owner/operators.
The PSN at Present
A prototype of the envisioned PSN network is already operated by
amateur seismologists in California who perform all the basic functions
of a PSN. They record seismograms from event-triggered digital
seismographs deployed in their own homes and upload the waveform
timeseries via modem to a PC-based BBS where the data is available to
PSN members and the public. On 28 June 1992, within a few hours of the
Landers, California Earthquake, we uploaded a waveform timeseries of
that event recorded by a PSN station in the Santa Clara Valley,
California to computers at the USGS in Golden, Colorado and gave a
hardcopy of the seismogram to the National Earthquake Information Center
(see Figure 1a). There are 50-100 PSN members and about 10 PSN stations
at present. The PSN currently operates BBSs in San Jose [(408)
226-0675], Pasadena [(818) 797-0536], and at the USGS in Menlo Park
[(415) 327-1517], California, and one in Memphis, Tennessee [(901)
360-0302]. The PSN also has a program to install seismographs and PSN
BBS links in the California public schools.
USGS Calnet stations in the hills surrounding the Santa Clara Valley
provide extensive source monitoring of local earthquakes (Eaton, 1991),
but only PSN seismographs regularly record ground motions on the valley
floor. Figure 1b displays the displacement seismogram of a local
microearthquake recorded by a PSN station at the Los Altos High School.
The undispersed character of the surface waves is similar to those
recorded by a temporary array deployed 10 km away to study the surface
waves converted from the body waves of Loma Prieta aftershocks (Frankel
et al., 1991). The large amplitudes and long durations of the surface
waves emphasize the important contribution of surface waves to strong
ground motions in sedimentary basins.
Site/Source Response
Site response is a measure of the amplification of ground motions
produced by local site conditions, e.g., sites underlain by soils
exhibit ground motions several times larger than those at sites
underlain by rock (Borcherdt, 1970). It is customarily assumed that the
site response is independent of source location, but the interference of
surface waves in sedimentary basins makes the ground motions at a
specific site a non-linear function of source location.
Consider the S-wave from a source below the center of a symmetric 2-D
sedimentary basin which generates two surface-wave pulses of equal
amplitude at opposite sides of the basin. The pulses propagate towards
each other across the basin and meet at the center, where their
amplitudes momentarily reinforce one another. The peak ground motion
will be twice as large at the center as at sites immediately adjacent to
it. If the source were shifted a small distance from the center, the
meeting point would be slightly shifted in the opposite direction.
Therefore, a small change in source location could lead to a
factor-of-two variation in peak amplitude at a specific site for two
otherwise identical sources.
Their sensitivity to site/source parameters suggest that the ground
motions of sedimentary basins may be chaotic phenomena. Lacking precise
information about the basin geometry and the temporal and spatial
sequence of fault slip, it may be as difficult to predict the ground
motion at a specific site as to predict the weather on 21 May next
year. Climate characterizes the chaotic phenomenon of the weather in
terms of its long-term behavior, i.e., many observations. The extreme
values of the temperature on 21 May and the probability that it will be
within a given range can be obtained from the historical record. The
PSN would provide a spatially dense array of stations, where ground
motion information is needed, which record the temporally complete
catalog of earthquakes distributed throughout the region. These data
would characterize the variation of the basin-wide pattern of site
response as a function of source and elucidate the mechanisms
responsible for this.
Conclusions
The disparity between the goal of comprehensive site-response
assessment of the increasingly populated seismically hazardous regions
of the Earth and the lack of ground motion data needed to do this calls
for a fundamental change in the means of high-frequency earthquake data
acquisition. Recent analysis of teleseismic waveforms recorded by
regional short-period networks (Benz and Vidale, 1993) emphasizes that
many low-quality stations can provide information not available from a
few high-quality stations. The technology to manufacture the required
seismographs and sensors and to maintain a telecommunications database
already exists; it is only a matter of employing it. The envisioned
seismograph would be able to record microearthquakes in the magnitude
range 1-2 at distances of 10-30 km within the urban area and so compile
an extensive record of ground motions associated with different
source/site combinations. It would also be able to record local
catastrophic, macroseismic events on-scale, and so be used to determine
the near-field details of the rupture process.
Many private citizens, particularly in seismically hazardous regions,
want to participate in a PSN. A PSN would directly connect scientific
observations -- instrumental recordings of ground motions -- to their
human consequences -- damage to buildings and other structures, i.e.,
Modified Mercalli Intensity. The complex "vascular system" of lifelines
(transportation, telephone, electricity, gas, water, sewage) requires a
"nervous system" of a dense seismic array to monitor the earthquake
hazards which threaten it. The data recorded by such dense arrays would
provide a solid empirical basis for our understanding of the response of
sedimentary basins.
References
Bard, P.Y., M. Campillo, F.J. Chaves-Garcia and F.J. Sanchez-Sesma
(1988). The Mexico earthquake of September 19, 1985: theoretical
investigation of large and small-amplification effects in the Mexico
City valley, Earthquake Spectra 4, 609-633.
Borcherdt, R.D. (1970). Effects of local geology on ground motion near
San Francisco Bay, Bull. Seism. Soc. Amer. 60, 29-61.
Cranswick, E., K. King, D. Carver, D. Worley, R. Williams, P. Spudich
and R. Banfill (1990). Site response across downtown Santa Cruz,
California, Geophys. Res. Lett 17, 1793-1796.
Cranswick, E., and R. Banfill (1990). Proposal for a high-density
people's seismograph array based on home computers in the San Francisco
Bay Area, EOS 71, 1469.
Eaton, J.P (1992). Determination of amplitude and duration magnitudes
and site residuals from short-period seismographs in Northern
California, Bull. Seism. Soc. Amer. 82, 533-579.
Frankel, A., S. Hough, P. Friberg and R. Busby (1991). Observations of
Loma Prieta aftershocks from a dense array in Sunnyvale, California,
Bull. Seism. Soc. Amer. 81, 1900-1992.
Frankel, A., and J. Vidale (1992). A three-dimensional simulation of
seismic waves in the Santa Clara Valley, California, from a Loma Prieta
aftershock, Bull. Seism. Soc. Amer. 82, 2045-2074.
Hanks, T. and Krawinkler, H. (1991). The Loma Prieta, California,
Earthquake and its effects: introduction to the special issue, Bull.
Seism. Soc. Amer. 81, 1415-1423.
Nolet, G. (1993). A Volksseismometer?, IRIS Newsletter 22, 10-11.
Papageorgio, A., and J. Kim (1991). Study of the propagation and
amplification of seismic waves in Caracas Valley with reference to the
29 July 1967 earthquake: SH waves, Bull. Seism. Soc. Amer. 81,
2214-2233.
Vidale, J.E. and H.M. Benz (1992). Upper-mantle seismic discontinuities
and the thermal structure of subduction zones, Nature 356, 678-683.
Figure 1. PSN recordings from the Santa Clara Valley, California. a)
1992 Landers, California Earthquake (magnitude 7.5, range 600 km)
recorded by an E-W horizontal seismometer with a natural period of 10
seconds. The record is severely clipped after the onset of the Sg
phase. b) Local microearthquake (1992 Sep 5 01:33 UTC, magnitude 2.0,
range 20 km) recorded by a N-S horizontal seismometer with a natural
period of 2 seconds. The original velocity timeseries has been
integrated to displacement. Note the extended duration of the SURFACE
waves.
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Large Quake???
Date: Thu, 01 May 1997 09:34:09 -0600
Vive La France!
Jean-Jacques HUNSINGER wrote:
>
> Dennis Leatart wrote:
> >
> > Hi Everyone!!
> >
> > I am picking up a large event that on first impression looks very
> > close-- but felt no motion here in Moorpark-- but the seismometer went
> > "full screen" for some time-- have seen no data on the web yet-- but
> > getting a good trace-- anyone else?? Time: 11:36 UT
> > --
>
> hello,
> I got the same at 12:12 UT here in France
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ct@....... (Charlie Thompson)
Subject: Re: Large Quake???
Date: Thu, 01 May 1997 11:50:58 -0500
WOW!
I'm about 976 miles from the Mag 6.7 in Mexico...It completely
saturated my preamp on the S-waves! Wow! I uploaded to PSN
if anyone wants to see what it's like to have a Lehman go
rail-to-rail. This is the largest teleseismic signal I've
ever recorded.
-Charlie Thompson
Buda, Texas
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Toward a jellybean seismometer
Date: Thu, 01 May 1997 13:38:15 -0600
Roger-
That is a very interesting summary of modern seismic sensor design that
you presented. I have never been very involved with the nitty-gritty of
sensor hardware design, so it illuminated some issues, such as the
relationship between sensitivity and Q, about which I had previously
heard but passed over without much thought. I discussed some of my
larger concerns in the "Recording Ground Motions Where People Live"
article that I posted this morning, but I will comment about a few
specific issues in your summary below:
roger baker wrote:
> The most favored locations for seismometers
> are on concrete piers or inside mines or in concrete enclosures, or best
> of all in deep bore holes (5; p 724-5).
The depends upon whether you want to study the seismic source
(earthquake or explosion, chemical or nuclear) or the hazardous effects
of ground shaking. Only the PSN is recording ground motions in the
Santa Clara Valley where over a million people of the San Francisco Bay
Area live; the USGS seismographs in the area are at "favored locations"
(according to the above) in the hills where few people live.
> However, this raises the interesting question of whether a small quartz
> or Pyrex filament and iron mass seismometer with capacitative detection
> plates could not be hermetically sealed within a test tube-like enclosure
> under high vacuum.
I have been waiting for Silicon Valley, home of the personal computer
and the 1906 San Francisco and 1989 Loma Prieta Earthquakes, to work
this out.
> There is no probably no need
> to increase instrumental sensitivity past the point that micro seismic
> background noise, from ocean waves and the like, dominates the data in
> those frequency bands.
The cultural noise -- seismic noise from freeways and everything else a
million people shake about in a technically advanced infrastructure
build in an alluvial basin -- is the limiting factor.
> Another issue is what sensitivities are desirable at low frequencies
> longer than about ten seconds. These very low frequencies are associated
> with the important major earthquake tremors that refract from deep layers
> and even travel through the center of the earth.
The frequency band of ground motions of interest to human society from
an engineering perspective is roughly 0.1 - 20.0 Hz, and this is (by
conincidence?) the frequency band of human mental processes, i.e., EEGs;
in other words, our perception response is peaked in this band.
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Re: Force Balance Progress
Date: Thu, 01 May 1997 22:17:26 -0700
Hi All --
Several people have asked about construction details of my force-balance
seismometer. Well.. At last I have a description posted on my web page.
(Actually, this is the only thing on my web page).
The URL is http://cnsii.com/karlc
If anyone has any questions, comments, criticisms, etc., please email me.
I have much of the design on a cad system at work, and generating other
diagrams that someone might want may be easy for me to do. Please ask.
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Toward a jellybean seismometer
Date: Thu, 01 May 1997 21:39:01 -0700
Edward Cranswick wrote:
> > There is no probably no need
> > to increase instrumental sensitivity past the point that micro seismic
> > background noise, from ocean waves and the like, dominates the data in
> > those frequency bands.
>
> The cultural noise -- seismic noise from freeways and everything else a
> million people shake about in a technically advanced infrastructure
> build in an alluvial basin -- is the limiting factor.
>
I have been looking at the possibility of an adaptive digital filter
which would help with this. Done in assembly code would be fast.
Barry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: Force Balance Progress
Date: Fri, 2 May 1997 08:29:28 -0800
Karl,
What a GREAT job of documenting your seismometer! Maybe someone else
knows, but wouldn't it be a good idea to write
"Copyright Karl Cunningham" on this somewhere. Wouldn't that prevent
someone from legally printing this up and selling it as their own
publication? Seems you could grant use for educational purposes but
not for resale.
Any lawyers out there?
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ct@....... (Charlie Thompson)
Subject: Lawyers and Seismology
Date: Fri, 02 May 1997 11:43:58 -0500
Question: What do you call 100 dead lawyers at the bottom of the sea?
Answer: A good start!
>Karl,
>
>What a GREAT job of documenting your seismometer! Maybe someone else
>knows, but wouldn't it be a good idea to write
>"Copyright Karl Cunningham" on this somewhere. Wouldn't that prevent
>someone from legally printing this up and selling it as their own
>publication? Seems you could grant use for educational purposes but
>not for resale.
>
>Any lawyers out there?
>
>JCLahr
>################################## John C. Lahr
>################################# Seismologist
>################################ U.S. Geological Survey
>############################### c/o Geophysical Institute
>############################## 903 Koyukuk Drive
>~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
>###########################################################
> P.O. Box 757320 ################################
> Fairbanks, AK 99775 #################################
> Phone: (907) 474-7997 ##################################
> Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
> lahr@........ ####################################
> http://www.aeic.alaska.edu/Input/lahr/
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jim Bone <jimbone@.........>
Subject: Re: Force Balance Progress
Date: Fri, 02 May 1997 09:46:52 -0700
Dr. John Lahr (USGS-GI Seismologist) wrote:
>
> Karl,
>
> What a GREAT job of documenting your seismometer! Maybe someone else
> knows, but wouldn't it be a good idea to write
> "Copyright Karl Cunningham" on this somewhere. Wouldn't that prevent
> someone from legally printing this up and selling it as their own
> publication? Seems you could grant use for educational purposes but
> not for resale.
>
> Any lawyers out there?
>
Not a lawyer, just a CPA (also USGS Volunteer when called by Pasadena),
but I believe Karl has copyright protection since he has put the words
in written (internet written) form and made them public. No one else
could copy the words and sell them. For additional protection Karl could
file a copy of the document with the US Government Patent office.
--
Jim Bone
jimbone@......... http://calproptax.com/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Michael J. Roseberry" <roseberry@...........>
Subject: Re: Force Balance Progress
Date: Fri, 02 May 1997 11:55:26 -0500
Dr. John Lahr (USGS-GI Seismologist) wrote:
>
> Karl,
>
> What a GREAT job of documenting your seismometer! Maybe someone else
> knows, but wouldn't it be a good idea to write
> "Copyright Karl Cunningham" on this somewhere. Wouldn't that prevent
> someone from legally printing this up and selling it as their own
> publication? Seems you could grant use for educational purposes but
> not for resale.
>
> Any lawyers out there?
Well, I'm not a lawyer but I understand from personal experience that
putting the phrase:
"Copyright (c) 1997 by <your name here>. All Rights Reserved."
will suffice to defend your claim of exclusive right to copy the
material for a certain length of time (few years).
Again, I'm not a lawyer; to be sure, you might want to check with one.
Michael J. Roseberry
--
_____________________
roseberry@...........
mjr@........
"There is no good substitute for understanding." -- mjr
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: JHammes@.........................
Subject: Re[2]: Force Balance Progress
Date: Fri, 2 May 1997 09:59:35 -0700
It was written:
>Karl,
>knows, but wouldn't it be a good idea to write
>"Copyright Karl Cunningham" on this somewhere. Wouldn't that prevent
>someone from legally printing this up and selling it as their own
>publication? Seems you could grant use for educational purposes but
>not for resale.
>Any lawyers out there?
>JCLahr
Karl,
All you need to do is put a copyright statement in the file to the
effect:"Copyright 1997 by Karl Cunningham". That sets it up. You can
use that nifty circled 'C' to replace the word Copyright.
Jerry Hammes
Harris Corp.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Re: Re[2]: Force Balance Progress
Date: Fri, 02 May 1997 10:30:14 -0700
Hi, All --
Thanks for all the comments about copyrighting. I am concerned about the
possibility of someone using what I've done for profit, and would much
prefer the information be available to all without charge. I'd rather not
have to be concerned with these issues, but this is the *real* world and I
guess I must.
I'll put a notice on.
Thanks again to all,
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: dsevold@.............. (Dean Sevold)
Subject: return calls
Date: Fri, 02 May 97 08:32:10 PDT
Pastey,
Well the situation here is that Dean is usually on line for a lot of hour=
s at nite which leaves almost zero time for me to get any news other than=
those who know e-mail. since you are the first e- mail to come my way =
in a coon's age, you know how exciting my life can be and how well inform=
ed I am. So sorry that you couldn't get through, but we did have the phon=
e line open for awhile after I talked to you. I can only hold Dean at =
bay for so many hours, you know??? But hey, thanks Valerie, it's good =
to know someone will help her mom out when she can't get through to peopl=
e! Besides, e-mail is kinda cool....
Well, good for Peter. I guess that Nathan will soon be wearing a tux for=
graduation, so I'll get to see what that looks like, too. I hope he loo=
ks good because it's costing us a mint.
I had a long phone call from a friend in Tofino last nite, if you tried =
to phone again. She had not phoned me for ages and it was because she =
was in real pain. I felt bad that she couldn't call me. Her sister died =
suddenly in January. This is her first major death in adulthood and I =
know she's been suffering. She was back in Vermont for the funeral and =
trying to help her mom out (in her 80's). Her sister was older than her,=
but there's all that sibling bonding that happens, you know. She and =
I talked a lot about death. Also talked alot about how people can't deal=
with death. It was a good phone call and I just wish that she had calle=
d before. Since I seem to be developing a whole list of people who have =
died, lately, I can definitely relate. I just hope that we can all make =
it through our lives without losing a son or daughter. I know that I wou=
ld be devastated to go through that, and for Wendy seeing her mom in that=
much pain was a tremendous eye-opener. She updated me on people in Tofi=
no, too. That's always interesting. Everyone has their stuff to deal =
with. Just think of Forrest. Run, Forrest, run......
So, on a brighter note, Jeffrey will have his birthday bash tomorrow in =
Victoria. We are spending the nite over there so that we don't have to =
run back for the goldarn ferry. This will feel good. Maybe I will find =
an answer to my questions for next fall there...... Victoria is a neat =
place.
Tony has been doing his photography with me, fairly successfully. We're =
going to try to start a business venture for him. He's dead broke and =
wants to do a lot, so this may help him feel more independent. Nathan =
is working 3 nites a week now. I'm hoping he'll figure that there might =
be a better way than being a pizza guy for life. Actually, I know what =
he wants, but I'm not sure how to get him on track.
I'm still working Tue-Thurs at the daycare.
Thanks for calling back. Sorry about our line, one of these days we'll =
be able to pay for a second line, but for now, we may be restricted to =
e-mail!!!!!!! Take care and hope that your insomnia isn't as bad as it =
gets for me and Zanny. We figure it's all part of menopausal crap and =
also the anxieties of growing children. At least when they were little =
we could sleep from pure exhaustion!!!! Ha.
Love you lots, Terry.
Hey, did Peter ever take a test in math called the Gauss test? Tony's =
about to take it and it looks like hell on wheels. There's grade 10 math=
and beyond in it and it's supposed to be for kids in grade 8. Makes me =
feel stupid....even Dean couldn't quite remember some of the stuff.... =
It's from the University of Waterloo. Could be interesting to see how =
this whole thing goes...wish him luck. (Since his name isn't too oriental=
, we know that he won't be in the top 40 in the country, the last test =
was won by all the lius, chus and los in the vancouver and ontario areas.=
Is this a Fuzzy statement in reverse?? No I just wonder how they do =
it. by the way, Tiger Woods is our hero. too bad for old Fuzzy, but may=
be he needs a brain shunt or something to help him out.....)
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Force Balance Progress
Date: Fri, 02 May 1997 21:54:35 -0700
Karl Cunningham wrote:
>
> Hi All --
>
> Several people have asked about construction details of my force-balance
> seismometer. Well.. At last I have a description posted on my web page.
> (Actually, this is the only thing on my web page).
>
> The URL is http://cnsii.com/karlc
>
> If anyone has any questions, comments, criticisms, etc., please email me.
Hi Karl-
I like the report also. I could only read to the middle of the LVDT
conditioner section. No more came to my screen.?? By the way Analog
Devices makes a LVDT complete signal conditioner in a single chip. It's
a AD598 I believe. Not cheap (about $25). I use one in a signal
condition box at work and it works great. It has an excitation
oscillator and also output conditioning from the LVDT.
Barry
PS- I also have a swinging gate Force Balance sensor (about 15" long).
It uses a capacitive bridge instead of LVDT but otherwise very similar
to yours. Mine is a little noisy but my protection for the sensor is not
as good as I would like ,yet. My measuring acceleration requires a
higher sampling rate since the frequencies measured are higher than
measuring velocity. My whole system ,with measuring velocity, was low
passed at 10 Hz but I need to increase it to about 20 Hz for the
acceleration measurements. This seems like a small price to pay for not
having to continually adjust for my Lehmans wandering. I haven't used
aluminum in any sensors because I was concerned about dissimilar metals;
though many have , so I guess it's not as much a problem as I thought.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "John A. Thomas" <jathomas@..........>
Subject: Re: Re[2]: Force Balance Progress -- Copyright
Date: Sat, 3 May 1997 08:28:57 -0700 (PDT)
OK, OK, I'm a patent and IP lawyer, so I'll delurk long enough to comment
on copyright.
Under the law since 1980, copyright exists as soon as the original work
of authorship is fixed in a tangible medium. Computer memory, disk, or
email is a fixation. So, you have your copyright automatically.
The copyright notice is not required, but it's a good idea. It puts
possible infringers on notice that the work is not in the public domain.
Registration with the copyright office is no longer required to create
the copyright; it's required before suing an infringer.
Remember that copyright only protects the _expression_, not the _ideas_
being expressed. The latter is the job of the patent law, and the
requirements for protection are much more stringent.
I'm collecting design ideas for a seismometer project of my own. I enjoy
the high level of technical discussion on this list.
----------------------------------------------------------------------
John A. Thomas | (972) 387-8880 | jathomas@..........
Dolce & Thomas, L.L.P. | Voice | jathomas@..............
5720 LBJ Fwy., Suite 470 | (972) 387-8881 |
Dallas, TX 75240 | Fax | PGP public key available
----------------------------------------------------------------------
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Wayne H. Francis" <francis@.............>
Subject: Re: Toward a jellybean seismometer
Date: Sat, 03 May 1997 10:33:39 -0700
Edward Cranswick wrote:
>
> Roger-
> That is a very interesting summary of modern seismic sensor design that
> you presented. I have never been very involved with the nitty-gritty of
> sensor hardware design, so it illuminated some issues, such as the
> relationship between sensitivity and Q, about which I had previously
> heard but passed over without much thought. I discussed some of my
> larger concerns in the "Recording Ground Motions Where People Live"
> article that I posted this morning, but I will comment about a few
> specific issues in your summary below:
>
> roger baker wrote:
>
> > The most favored locations for seismometers
> > are on concrete piers or inside mines or in concrete enclosures, or best
> > of all in deep bore holes (5; p 724-5).
>
> The depends upon whether you want to study the seismic source
> (earthquake or explosion, chemical or nuclear) or the hazardous effects
> of ground shaking. Only the PSN is recording ground motions in the
> Santa Clara Valley where over a million people of the San Francisco Bay
> Area live; the USGS seismographs in the area are at "favored locations"
> (according to the above) in the hills where few people live.
> <snip>
> --
> Edward Cranswick Tel: 303-273-8609
> US Geological Survey, MS 966 Fax: 303-273-8600
> 1711 Illinois St cranswick@........
> Golden, CO 80401 USA E.M. Forster said, "Only connect".
<snip>
This brings me back to a question I posed to the group back during
the Christmas holidays and to which I never got an answer:
When I finally get a seismometer built (thanks to the wealth of
info in this group) I had intended to install it in my pumphouse -
concrete slab, 150 foot well with 11 inch steel casing down through the
middle. As a novice to seismo stuff, I don't know whether this is a
very good idea (with a 150 foot earth antenna, so to speak), or a very
bad idea because of whatever noise at whatever frequencies may be
occurring (the well is running artesian right now). The pump would run
very infrequently...haven't operated it for a coupla years.
(Interestingly, the well is part of my EQ preparedness program...guess
I'll turn the well on and the seismometer off after the big one hits).
If it's an unknown, I'm willing to experiment to see what the effect is,
but if somebody already knows I'd appreciate the wisdom of the list so I
can plan the relocation. Thanks in advance. Wayne
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: M6.9 quake in the Kermadecs
Date: Sun, 04 May 1997 09:34:36 +1200
hi all ,
nice event in the early hours of this morning NZST largest
amp. quake so far recorded with SDR. it has been uploaded to Larry's
events file
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: I should clarify
Date: Sun, 04 May 1997 09:50:11 +1200
the M 6.9 stated for the Kermadec event was from the NZ seismological Obs.
The USGS gave it a Mb 6.6
Also Malcolm Sinclair in Christchurch city (see his station data on
the PSN map) got his drum recorder going yesterday and then was treated to
his first recorded event today (a good one too) talk about beginners luck !!
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: General info
Date: 03 May 97 21:10:03 EDT
Hi gang,
Two items of interest from Physics Today, May 1997:
1. The Am. Geophys. Union has established a medal in honor of Inge Lehmann
[note 2 n's, not the seismometer designer]. She was the pioneering Danish
seismologist who discovered the existance of Earth's inner core in 1936. page
54.
2. A long and very favorable review of "Shocks & Rocks:Seismology in the Plate
Tectonics Revolution" by Jack Oliver, AGU 1996 208 pp $28, is on page 63. This
is in the AGU's series on the history of geophysics.
"Jack Oliver has made a valuable contribution to our understanding of the plate
tectonics revolution, and young scientists will profit from reading this book."
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Rond <rond@................>
Subject: Re: seismocam
Date: Sun, 04 May 1997 01:31:32 -0500
Dave,
>here it is in real time updated every 5 minutes you can see tonites events
>
>http://www.knbc4la.com/seismo/images/seismoNow.jpg
I'm almost certain your new SEISMOCAM web page was used in a "bit" on Jay
Lenow's Tonight Show a few nights ago. Do you get that program down your way?
Anyone else see the program and recognize the recorder?
I wasn't aware that he credited you, your Web site or anyone else at the time.
Charlie Rond -\/\--Public Seismic Network-Memphis
rond@................ (901) 360-0302 [ free BBS ]
http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: seismocam
Date: Sun, 04 May 1997 19:12:34 +1200
greetings Charlie R.,
for your info (an all else) there is
another seismo cam site from the University of Nevada, Reno at
http://www.seismo.unr.edu/Webcam/webcam.html
unlike the other recorder which is a standard Kinmetrics 1 rotation / 15
mins this one is a helicorder, it spreads the lines out still covers 24
hrs but rotates a lot slower ~ 1inch per minute .... 1 rotation / hr
the 6.7 event from Mexico the other day looked brilliant on this one
todays Kermadec event did show up but obviously no where near the same
amplitude.
Dave
BTW no we don't get Jay's Tonight Show down this was (I am aware of it
though) we do get David Letterman nightly Is Jay any better or worse ???
The other seismocam page isn't mine it's NBC's in LA
At 01:31 AM 5/4/97 -0500, you wrote:
>Dave,
>>here it is in real time updated every 5 minutes you can see tonites events
>>http://www.knbc4la.com/seismo/images/seismoNow.jpg
>
>I'm almost certain your new SEISMOCAM web page was used in a "bit" on Jay
>Lenow's Tonight Show a few nights ago. Do you get that program down your way?
>Anyone else see the program and recognize the recorder?
>I wasn't aware that he credited you, your Web site or anyone else at the time.
> Charlie Rond -\/\--Public Seismic Network-Memphis
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: [Fwd: chart recorders]
Date: Sun, 04 May 1997 08:33:18 -0700
Can anyone help this gentleman?
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
The following request from Stan Williams at ASU seeks replacements for
chart recorder pens. Please send information directly to Stan at
Stanley.Williams@........ do not use "Reply" to respond.
----------------------------Original message----------------------------
I am desperately trying to find a new pen for my old, but wonderful, HP chart
recorder. It seems to be very difficult because the chart recorder is years
past HP manufacturing them and they have no supplies of pens. The company
to which they recommend I turn is no longer carrying plotter pens. There
must be substitute sources for such old but still-working equipment. I am
looking for a small (1 cm across, 4 mm thick, and 3 cm long) plastic pen
(essentially a felt tip nub) which slides into a bracket on the HP 7155
chart recorder. Any suggestions of a source for purchase of new pens or how
to rejuvenate the old cartridges would be much appreciated.
cheers,
stan
Stanley N. Williams, Professor of Volcanology
Department of Geology
Box 871404
Arizona State University
Tempe, AZ 85287-1404 USA
Telephone: 602-965-1438, Fax: 602-965-8102, Home: 602-598-9008
E-mail: Stanley.Williams@.......
From: roger baker <rcbaker@........>
Subject: Re: [Fwd: chart recorders]
Date: Sun, 4 May 1997 12:02:54 -0500 (CDT)
Dear Charles,
What I would suggest is blending a mixture of food coloring
or some other dye such as gentian violet with a little glycerine to keep
it from drying out o the tip. Then put an ounce or so in a bottle big
enough to hold the pen. Then stopper the bottle and draw a vacuum on the
bottle until the air in the pen is expelled. Then release the vacuum and
the ink should fill up the pen. Then wipe with a damp paper towel. Use a
razor blade to sharpen up the tip if necessary. Ther are probably also
ways to jury rig other pens to work.
--Yours, Roger Baker
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Bradley A. Rogers" <rogersb@...........>
Subject: Rookie Questions
Date: Sat, 4 May 1996 14:41:22 -0400
OK, folks, its rookie questions time. Building a seismometer is =
something that I've wanted to do for years, but I've only recently =
gotten serious about it. After lurking on this list for a while, and =
reading the FAQs and other sources of info, I would like to solicite the =
group's opinion on several questions:
1) I live in upstate New York, so will be primarily detecting =
teleseismic events. My understanding is that for purposes of detecting =
such events, a longer period seismometer is better. True, or false?
2) What would be the upper and lower bounds on the periods I would want =
to consider?
3) Given that I have nearly zero background in the way of electronics, =
what style of sensor makes the most sense? I'm interested in using this =
project to broaden my horizons, so I'm inclined not to buy my amps, etc. =
But I also don't want to bite off more than I can chew. (I'd also like =
to get this thing up and running sometime in the not too distant =
future!).
Thanks for any advice!
--Brad Rogers =
(rogersb@............
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Charles R. Patton" <patton@.........>
Subject: Re: Force Balance Progress
Date: Sun, 04 May 1997 19:10:56 -0700
Karl,
First off, allow me to say I think your FB construction article is
great. One thought I had was if you would ZIP it and the photos
together and put a pointer to the .zip file at the beginning of the
article -- it could be downloaded faster and easier. (See note below
about LVDT chips.)
I feel like I'm in competition! Eric Kern and I have been working on
using the Humphrey accelerometer in a seismometer with a 30 ug to 2 g
range. One big advantage to the Humphrey accelerometer is that is only
0.6" in diameter for two axis and with DC response, we can design for
any low end response we need, and by using two units, we can do all 3
axis. I've been publishing the analysis and schematics in the
Geo-Monitor starting in March as a continuing project. If we get some
interest, we'll make up circuit boards for this project. The whole 3
axis board, exclusive of the power supply (transformers are big, hot,
and hum generators!), but with the A/D and computer interface, could be
2" x 4" or so. That should make mounting on a pier or whatever a lot
easier. So, if you're interested, please let me know, so we can gauge
interest. Cost is likely to be in the $150 to $200 range for everything
complete, ready to plug into your computer. Incidently, I'ld like to
know how many people want an analog output. It can actually be easier
to go directly to the computer, using the A/D. To drive a local strip
chart with sufficient gain and signal conditioning would actually be
harder, so I just as soon forgo that in a kit, if possible. But I know
several people have mentioned that they still have a strip chart
attached to their seimometers.
Also Barry Lotz wrote:
....Analog Devices makes a LVDT complete signal conditioner in a single
chip...
But also Signetics (now Philips) also makes an LVDT chip. Look at:
http://www.semiconductors.philips.com/cgi-bin/searchcat?cat=5999&code=19
where you will find the following pointerers to PDF files:
NE/SA5521 LVDT Signal Conditioner
AN1183 NE/SA/SE5521 Position Measurement
AN1182 Using The NE5521 Signal Conditioner In
Multi-Faceted Applications
These chips have been around at least since '94.
Charles R. Patton, Editor, Geo-Monitor
patton@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert Avakian <ravakian@............>
Subject: Re: Toward a jellybean seismometer
Date: Sun, 04 May 1997 15:16:46 -0700
Wayne H. Francis wrote:
>
> Edward Cranswick wrote:
> >
> > Roger-
> > That is a very interesting summary of modern seismic sensor design that
> > you presented. I have never been very involved with the nitty-gritty of
> > sensor hardware design, so it illuminated some issues, such as the
> > relationship between sensitivity and Q, about which I had previously
> > heard but passed over without much thought. I discussed some of my
> > larger concerns in the "Recording Ground Motions Where People Live"
> > article that I posted this morning, but I will comment about a few
> > specific issues in your summary below:
> >
> > roger baker wrote:
> >
> > > The most favored locations for seismometers
> > > are on concrete piers or inside mines or in concrete enclosures, or best
> > > of all in deep bore holes (5; p 724-5).
> >
> > The depends upon whether you want to study the seismic source
> > (earthquake or explosion, chemical or nuclear) or the hazardous effects
> > of ground shaking. Only the PSN is recording ground motions in the
> > Santa Clara Valley where over a million people of the San Francisco Bay
> > Area live; the USGS seismographs in the area are at "favored locations"
> > (according to the above) in the hills where few people live.
>
> > <snip>
>
> > --
> > Edward Cranswick Tel: 303-273-8609
> > US Geological Survey, MS 966 Fax: 303-273-8600
> > 1711 Illinois St cranswick@........
> > Golden, CO 80401 USA E.M. Forster said, "Only connect".
>
> <snip>
>
> This brings me back to a question I posed to the group back during
> the Christmas holidays and to which I never got an answer:
>
> When I finally get a seismometer built (thanks to the wealth of
> info in this group) I had intended to install it in my pumphouse -
> concrete slab, 150 foot well with 11 inch steel casing down through the
> middle. As a novice to seismo stuff, I don't know whether this is a
> very good idea (with a 150 foot earth antenna, so to speak), or a very
> bad idea because of whatever noise at whatever frequencies may be
> occurring (the well is running artesian right now). The pump would run
> very infrequently...haven't operated it for a coupla years.
> (Interestingly, the well is part of my EQ preparedness program...guess
> I'll turn the well on and the seismometer off after the big one hits).
> If it's an unknown, I'm willing to experiment to see what the effect is,
> but if somebody already knows I'd appreciate the wisdom of the list so I
> can plan the relocation. Thanks in advance. Wayne
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
Wayne's message brings up a point that has bothered me for some while
although this is probably not the palce to ask. Is there a way to find
out the physical location of a site, com, net or org or the full name of
the site, if they do not provide any hint in the message?
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Rond <rond@................>
Subject: Re: seismocam
Date: Mon, 05 May 1997 04:45:40 -0500
Dave,
>greetings Charlie R.,
>for your info (an all else) there is another seismo cam site
>from the University of Nevada, Reno at
>http://www.seismo.unr.edu/Webcam/webcam.html
>BTW no we don't get Jay's Tonight Show down this was (I am aware of it
>though) we do get David Letterman nightly. Is Jay any better or worse ???
It's all a matter of taste. I like Jay better.
>The other seismocam page isn't mine it's NBC's in LA
I would have realized that had I looked at the URL more closely.
As it was, I gave you lots of glory and bragged on you to folks.
I've bragged on you before - map, etc. - and will again. But with
the seismocam, I was confusing your enthusiasm with ownership. My
apologies to you and the clever folks at NBC.
Charlie Rond -\/\--Public Seismic Network-Memphis
rond@................ (901) 360-0302 [ free BBS ]
http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David Alexander <dalex@...........>
Subject: Re: [Fwd: chart recorders]
Date: Mon, 05 May 1997 09:25:04 -0700
Charles Watson wrote:
>
> Can anyone help this gentleman?
>
> --
> ---/----
> Charles P. Watson, Consulting Geologist
> Advanced Geologic Exploration
> Seismo-Watch / Earthquake Information Services
> Voice: 702-852-0992 / Fax: 702-852-3226
> mailto:watson@................
> http://www.seismo-watch.com
>
> ---------------------------------------------------------------
>
> Subject: chart recorders
> Date: Sun, 4 May 1997 07:50:58 MST
> From: "Stanley N. Williams" <stanley.williams@.......>
> Reply-To: VOLCANO <VOLCANO@..................>
> To: VOLCANO@..................
>
> The following request from Stan Williams at ASU seeks replacements for
> chart recorder pens. Please send information directly to Stan at
> Stanley.Williams@........ do not use "Reply" to respond.
>
> ----------------------------Original message----------------------------
>
> I am desperately trying to find a new pen for my old, but wonderful, HP chart
> recorder. It seems to be very difficult because the chart recorder is years
> past HP manufacturing them and they have no supplies of pens. The company
> to which they recommend I turn is no longer carrying plotter pens. There
> must be substitute sources for such old but still-working equipment. I am
> looking for a small (1 cm across, 4 mm thick, and 3 cm long) plastic pen
> (essentially a felt tip nub) which slides into a bracket on the HP 7155
> chart recorder. Any suggestions of a source for purchase of new pens or how
> to rejuvenate the old cartridges would be much appreciated.
> cheers,
> stan
>
> Stanley N. Williams, Professor of Volcanology
> Department of Geology
> Box 871404
> Arizona State University
> Tempe, AZ 85287-1404 USA
> Telephone: 602-965-1438, Fax: 602-965-8102, Home: 602-598-9008
> E-mail: Stanley.Williams@.......
i am sending an answer to the whole list as it might be of interest to
others
looking in the Thomas Register i found the following places listing
pens.
Graphic Control 1800-669-1535
Technical Sales and Service 1800-374-7055
Charts Inc. 1800-882-9357
Dia-Neilson 609-829-9441
i don't vouch for any of these. i didn't try the numbers, so some of
them may not still be around. 'tis suprising how fast companies come
and go.
cheers
dave k7da
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Force-bal seismometer Karl C.
Date: 05 May 97 14:20:04 EDT
Karl Cunningham,
Your web page at cnsii.com/karlc is an exemplary design--easy to get around,
etc. Your description of your force balance seismometer is very interesting and
contains nearly all necessary details (as far as it goes, see later).
I agree with your not using a knife edge on the pivot end of the boom, that is
bad kinematics--I use essentially a point resting on a flat. However, I find
that <not> having a dimple makes it easier to position the end of the boom and I
have seen no suggestion of instability. (I spent all day yesterday increasing
the period of my Lehman from 16 to 35 secs. Of course, this required reducing
the damping. It is now much more finicky about centering but I am trying it for
at least a few days to see if this is too annoying.)
Using a guitar tuning mechanism is a neat trick. I'm curious if experience
dictated use of the 2-part suspension. I see no problem just using piano wire.
I plan to build your LVDT to play with it--your descrption makes it sound
straightforward. Values for R301 & R302 are not given on your schematic. I
know not why but your web page seems to end in the LVDT Output Conditioner
section with the sentence:"The ratio of excitation frequency of 5kHz to this 10
Hz filter give...". I accessed your page thrice and it terminated at exactly
the same place. Maybe my Worldnet browser is getting tired but it seems to work
for other things. I suppose the feedback circuit, etc., follows the part which
I have. I'm dying to read the rest of your dissertation!
Who makes the DG419 synchronous demodulator and where can I buy one or a few?
As you may know, I sent a description on my meter-movement calibration device
to Cochrane's archives. I use it daily to observe any sensitivity changes.
Since you already have a means of applying a known force using an electrical
signal (the 520 grams-force/amp), I wonder if you have considered applying
pulses to your force balance coil for the purpose of calibrating the whole
seismometer.
Thanks for taking the trouble of writing up your experiment. Be sure to keep
us informed about its performance.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Force-balance web page problem
Date: Mon, 05 May 1997 12:13:37 -0700
Hi All --
There seems to have been some problem at my ISP with my force balance web
page. The page somehow got truncated at 15000 bytes exactly; it should be
about 26K long.
I think I have a work-around in place now, so if you only received down to
the LVDT Output Conditioner part, please reload the page to see the rest.
Sorry for the inconvenience.
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Greg Lyzenga <lyzenga@.................>
Subject: Re: Force Balance Progress
Date: Mon, 05 May 1997 16:31:04 -0700
>... By the way Analog
>Devices makes a LVDT complete signal conditioner in a single chip. It's
>a AD598 I believe. Not cheap (about $25). I use one in a signal
....
>
>But also Signetics (now Philips) also makes an LVDT chip. Look at:
>http://www.semiconductors.philips.com/cgi-bin/searchcat?cat=5999&code=19
>
>where you will find the following pointerers to PDF files:
>NE/SA5521 LVDT Signal Conditioner
>AN1183 NE/SA/SE5521 Position Measurement
>AN1182 Using The NE5521 Signal Conditioner In
>Multi-Faceted Applications
>
Hi Folks:
I have been following with great interest this discussion on the
force-feedback design and Karl Cunningham's *great* web page. I was
particularly interested in the mention of these all-in-one chips that
promise to greatly simplify the design and fabrication problems.
I have a question though, which I hope won't seem too dumb-sounding. The
instrument I am contemplating building will use a differential capacitance
transducer, rather than the LVDT. From my understanding of the theory
behind these things, I can see no reason why these conditioner chips would
not work just as well on a capacitance instrument. The basic idea seems
identical: drive the transducer with a stable oscillator, and then observe
and demodulate/rectify the out-of-balance signal between the two legs.
The fact that no mention of this application is made in the description or
notes for the device makes me suspicious though. So, am I right that the
chips could be used in this way? Or am I all wet? Thanks for any help or
comments!
- Greg Lyzenga
|Gregory A. Lyzenga <lyzenga@.................> *** (909) 621-8378
|Dept. of Physics, Harvey Mudd College *** fax (909) 621-8887
|Claremont, CA 91711-5990
http://www.physics.hmc.edu/profs/lyzenga.html
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Charles R. Patton" <patton@..........>
Subject: Re: Force Balance Progress (capacitance question)
Date: Mon, 05 May 1997 17:34:35 -0700
Greg Lyzenga asked:
(Can I use)...use a differential capacitance transducer, rather than the
LVDT...(with a single chip solution?)
Unfortunately, no, the impedances and frequencies are all wrong in those
chips. There are several companies that make a single chip solution for
capacitance. Capacitance is the changing factor in many manometers such
as pressure and vaccuum meters. So companies like Setra have a custom
chip that is used in their equipment. Unfortunately Setra doesn't sell
the chips -- We had a possible application that fell through in part
because they didn't want to sell them. There is a company called CSEM
in France (?) that has chips, and I believe they may be a standard
product, but I never followed it up. Recently
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Charles R. Patton" <patton@..........>
Subject: Re: Force Balance Progress
Date: Mon, 05 May 1997 17:52:51 -0700
Greg Lyzenga asked:
(Can I use)...use a differential capacitance transducer, rather than the
LVDT...(with a single chip solution?)
Unfortunately, no, the impedances and frequencies are all wrong in those
chips. There are several companies that make a single chip solution for
capacitance. Capacitance is the changing factor in many manometers such
as pressure and vaccuum meters. So companies like Setra have a custom
chip that is used in their equipment. Unfortunately Setra doesn't sell
the chips -- We had a possible application that fell through in part
because they didn't want to sell them. There is a company called CSEM
in France (?) that has chips, and I believe they may be a standard
product, but I never followed it up. Recently
---sorry for the premature previous message - I hit Ctl-H ---
Electronic Design magazine of November 4, 1996 in the Ideas for Design
on page 110 had a 2 IC capacitor bridge design, which is a very
sensitive and accurate way to do the task (5 mV/pF and a resolution of
10fF). Add one more IC and it gets really sensitive (5 V/pF and can
resolve 2 fF).
Also you might check out two papers, "A Very Accurate Measurement
System for Multielectrode Capacitive Sensors", and "A Novel Low-Cost
Capacitive-Sensor Interface", pages 531-540 of IEEE Transactions on
Instrumentation and Measurement, Vol. 45, No. 2, April, 1996. The one
paper covers measuring 2 pF with an accuracy of 100 ppm and resolution
of 50 aF. The only problem was it took 300 ms per measurement.
Anyway some possible avenues you might explore.
Charles Patton
patton@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Force Balance Progress
Date: Mon, 05 May 1997 19:22:55 -0700
Greg Lyzenga wrote:
>
> >... By the way Analog
> >Devices makes a LVDT complete signal conditioner in a single chip. It's
> >a AD598 I believe. Not cheap (about $25). I use one in a signal
> ...
> >
> >But also Signetics (now Philips) also makes an LVDT chip. Look at:
> >http://www.semiconductors.philips.com/cgi-bin/searchcat?cat=5999&code=19
> >
> >where you will find the following pointerers to PDF files:
> >NE/SA5521 LVDT Signal Conditioner
> >AN1183 NE/SA/SE5521 Position Measurement
> >AN1182 Using The NE5521 Signal Conditioner In
> >Multi-Faceted Applications
> >
>
> Hi Folks:
> I have been following with great interest this discussion on the
> force-feedback design and Karl Cunningham's *great* web page. I was
> particularly interested in the mention of these all-in-one chips that
> promise to greatly simplify the design and fabrication problems.
>
> I have a question though, which I hope won't seem too dumb-sounding. The
> instrument I am contemplating building will use a differential capacitance
> transducer, rather than the LVDT. From my understanding of the theory
> behind these things, I can see no reason why these conditioner chips would
> not work just as well on a capacitance instrument. The basic idea seems
> identical: drive the transducer with a stable oscillator, and then observe
> and demodulate/rectify the out-of-balance signal between the two legs.
>
> The fact that no mention of this application is made in the description or
> notes for the device makes me suspicious though. So, am I right that the
> chips could be used in this way? Or am I all wet? Thanks for any help or
> comments!
>
> - Greg Lyzenga
>
Hi Greg
I currently use a capacitive bridge with a swinging gate Force
Balance sensor I put together and am currently analizing. It works fine
so far. The circuit is a little noisy but I'm not sure it has to do with
the bridge. My environmental protection is not very good as yet.-- Not
to mention Analog Devices again, but they have a new chip (AD 698) which
shows a cap. bridge in their sample circuits. I tried to get one a few
months ago but they were not available as yet. I have resorted to an
alternate circuit which I saw in Circuit Cellar. I'll send you a GIF
picture which you can look at and modify as necessary.
Barry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: remote sensor
Date: Mon, 05 May 1997 20:13:20 -0700
I have been planning for a compact remote sensor which will pick events
outside the urban environment. I plan to have a digital filter,
freq/amp
dependent trigger routine an PCMCIA for storage. All the pieces are
working but need to be put together. What I can't seem to find a very
good selection of are very low power 16 bit processors. 8088 is to
slow.
286 up would work (12+ Mhz). I am familiar with some SBC's but nearly
all are 8 bit or use to much power. There was one company back east
which claimed they had an all CMOS 386 board which drew 0.1 watts. I am
skeptical. Any thing under 50 ma @ 3.3-5v would be great. I could
incorporate solar w/ a battery. V20 boards I've seen but the source
sounded like there was a 64k limit and only took C routines,which is
not
my strong language. Any input would be appreciated.
Barry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Re: [Fwd: chart recorders]
Date: 06 May 97 10:55:13 EDT
I have adapted ball point pens to my HP X-Y recorder. Some of these work very
well.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Humphrey accelerometer
Date: 06 May 97 10:55:09 EDT
Charles Patton,
Your seismometer design using a Humphrey accelerometer sounds interesting.
Could you describe the Humphrey and/or tell us where to look for a detailed
description? Who makes them and what do they cost, etc?
You say that the Humphrey has a range of 30 micro-g to 2 g. I'm wondering if
this is enough sensitivity for teleseismic events (the only kind I get). Aki &
Richards, "Quant. Seismology" vol 1 p 494
sez that a M6 quake at a distance of 80 deg would have Rayleigh wave (with a
period of 20", the period of minimum attenuation) accelerations of 10e-7 g. The
really interesting phases, P & S, are usually much smaller--perhaps 10e-8 g.
Thus, it looks like the Humphrey falls short by a factor of perhaps 3,000.
Since I already have Cochrane's A/D board so that I can use SDR with my
Lehman, I would need an analog output to use your system.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Rookie Questions
Date: Tue, 06 May 1997 18:26:46 -0700
Hi Brad,
At 02:41 PM 5/4/96 -0400, you wrote:
>OK, folks, its rookie questions time. Building a seismometer is something
that I've >wanted to do for years, but I've only recently gotten serious
about it. After lurking >on this list for a while, and reading the FAQs
and other sources of info, I would like >to solicite the group's opinion on
several questions:
>
>1) I live in upstate New York, so will be primarily detecting teleseismic
events. >it is understanding is that for purposes of detecting such
events, a longer period >seismometer is better. True, or false?
True.
>
>2) What would be the upper and lower bounds on the periods I would want
to consider?
For teleseismic events maybe 10 seconds to 60 seconds.
>
>3) Given that I have nearly zero background in the way of electronics,
what style of >sensor makes the most sense? I'm interested in using this
project to broaden my >horizons, so I'm inclined not to buy my amps, etc.
But I also don't want to bite off >more than I can chew. (I'd also like to
get this thing up and running sometime in the >not too distant future!).
Constructing a good stable sensor can be hard enough, be it a Lehman or SG
sensor.
If you haven't build any electronic breadboards before, making an
amplifier/filter board for the Lehman, or the electronics part of the SG
sensor, and, an A/D card (or you can use a chart recorder at this point),
and, writing the software to display the information if you us an A/D card
is a major task.
> Thanks for any advice!
> --Brad Rogers (rogersb@............
Good luck...
-Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Rookie Questions
Date: Tue, 06 May 1997 18:59:45 -0700
Larry Cochrane wrote:
>
> Hi Brad,
>
> At 02:41 PM 5/4/96 -0400, you wrote:
> >OK, folks, its rookie questions time. Building a seismometer is something
> that I've >wanted to do for years, but I've only recently gotten serious
> about it. After lurking >on this list for a while, and reading the FAQs
> and other sources of info, I would like >to solicite the group's opinion on
> several questions:
> >
> >1) I live in upstate New York, so will be primarily detecting teleseismic
> events. >it is understanding is that for purposes of detecting such
> events, a longer period >seismometer is better. True, or false?
>
> True.
>
> >
> >2) What would be the upper and lower bounds on the periods I would want
> to consider?
>
> For teleseismic events maybe 10 seconds to 60 seconds.
>
> >
> >3) Given that I have nearly zero background in the way of electronics,
> what style of >sensor makes the most sense? I'm interested in using this
> project to broaden my >horizons, so I'm inclined not to buy my amps, etc.
> But I also don't want to bite off >more than I can chew. (I'd also like to
> get this thing up and running sometime in the >not too distant future!).
>
> Constructing a good stable sensor can be hard enough, be it a Lehman or SG
> sensor.
> If you haven't build any electronic breadboards before, making an
> amplifier/filter board for the Lehman, or the electronics part of the SG
> sensor, and, an A/D card (or you can use a chart recorder at this point),
> and, writing the software to display the information if you us an A/D card
> is a major task.
>
> > Thanks for any advice!
> > --Brad Rogers (rogersb@............
> Good luck...
>
> -Larry Cochrane
> Redwood City, PSN
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
I've used Sams "Op-amp Circuits and Principles" often. It's basic and
not to lengthy ( for reference on the analog portion of the circuit).
Barry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: New seismometer
Date: Wed, 7 May 1997 14:31:51 -0800
> From r-lewis5@...... Wed May 7 03:42 AKD 1997
> MIME-Version: 1.0
> Content-Transfer-Encoding: 7Bit
> To: "John C Lahr, Fairbanks, AK "<lahr@.................>
> From: Bob Lewis <r-lewis5@......>
> Subject: New seismometer
> Date: Wed, 7 May 1997 06:42:59 -0700
> X-BeyondMail-Priority: 1
> Conversation-Id: <BMSMTP8630121941a0108146@..................>
> X-Receipt-From-Agent: true
>
> I got some information in the mail the other day from PMD Scientific; they are
> the outfit that supplies the Princeton Earth Physics Project. I have the data
> sheet for their 3-component broadband seismometer that they compare to the
> Strecheisen in performance. It is 7" in diameter and 5" tall, and they say
> that it has NO MOVING PARTS, using something they call "molecular electronic
> technology", developed in part by the National Science Foundation. How do make
> a device to sense motion with no moving parts? For $2600 it is a LOT cheaper
> than say an STS-2.
>
> I thought I would see if you have heard of this instrument and if you know how
> it operates. I would be happy to fax or mail the data if you like.
>
>
Hi Bob,
I know of the PMD seismometer and even have some seismograms they sent with
comparisons of the PMD to the STS2. I sure don't know how they work, however.
Mayber someone on the PSN list knows.
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ACole65464@.......
Subject: Re: Rookie Questions
Date: Wed, 7 May 1997 21:54:13 -0400 (EDT)
Brad,
This reply may help others that may be a "lurker" and as of yet not ready to
step up to the plate and build a simple seismometer because an electronic
schematic scares you.
A good learning tool that got me started to at least construct electronic
circuits and build up my confidenece, was to build circuits using one of
those Radio Shack "30-in-1 Electronic Lab" or similar kits. These kits will
go through the steps of building a circuit per a schematic, plus you can
build many different circuits with their 300-in-1 kit. The next step is to
buy indiviual parts, same as the kit parts, and per the schematic, solder
wires to them on a piece of perf board. That way you will replicate a circuit
that you know works and it is easier to debug if you copy exactly the
predesigned circuit.
Be patient if you blow up several parts in the process. It will be a good way
to learn if you have no one else to teach you the basics.
That's my input.
Bye for now,
Allan Coleman
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Rookie Questions
Date: Wed, 07 May 1997 21:49:02 -0700
ACole65464@....... wrote:
>
> Brad,
> This reply may help others that may be a "lurker" and as of yet not ready to
> step up to the plate and build a simple seismometer because an electronic
> schematic scares you.
> A good learning tool that got me started to at least construct electronic
> circuits and build up my confidenece, was to build circuits using one of
> those Radio Shack "30-in-1 Electronic Lab" or similar kits. These kits will
> go through the steps of building a circuit per a schematic, plus you can
> build many different circuits with their 300-in-1 kit. The next step is to
> buy indiviual parts, same as the kit parts, and per the schematic, solder
> wires to them on a piece of perf board. That way you will replicate a circuit
> that you know works and it is easier to debug if you copy exactly the
> predesigned circuit.
> Be patient if you blow up several parts in the process. It will be a good way
> to learn if you have no one else to teach you the basics.
> That's my input.
> Bye for now,
> Allan Coleman
>
$0.02
I use solderless breadboards all the time. They are simple and you
can move things around at will.
Barry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Aart Olsen <aart@........>
Subject: Re: New seismometer
Date: Thu, 08 May 1997 08:36:43 -0500
Well "no moving parts" isn't a big deal. Force-balancing accelerometers
generally have no moving parts -- that's the whole idea: f-f=ma=0. The
three axis seismometer I'm building uses a bowling ball rigidly held in a
plywood box, with piezo film sensors at the six contact points.
>> From r-lewis5@...... Wed May 7 03:42 AKD 1997
>> I got some information in the mail the other day from PMD Scientific;
they are
>> the outfit that supplies the Princeton Earth Physics Project. I have
the data
>> sheet for their 3-component broadband seismometer that they compare to the
>> Strecheisen in performance. It is 7" in diameter and 5" tall, and they say
>> that it has NO MOVING PARTS, using something they call "molecular
electronic
>> technology", developed in part by the National Science Foundation. How
do make
>> a device to sense motion with no moving parts? For $2600 it is a LOT
cheaper
>> than say an STS-2.
Aart M. Olsen mailto:aart@........ 217-244-4688
Library Systems Office Univ of Illinois at Urbana-Champaign
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Seism0man@.......
Subject: Re: jelly bean seismology
Date: Thu, 8 May 1997 23:51:16 -0400 (EDT)
Hi this is the first time writing yo guys. Anyway to the point. I have
built a very in expensive amplifier that will connect serially to anybody's
IBM compatible computer. I have started to write the software (WIN 95 Visual
Basic). Then I had an epifany. The GEOPHONE!!!! I fyou could use the
geophone with my amplifier and rewrite the software to email on the event of
a detectable earthquake, you could effectively have you jellybean seismometer
for about $80 US. The geophone I imagine would be omni-directional or at
least vertical. That would be a complete seismograph that would be easily
placed about anywhere. Indiscriminate enough to hide or bury at somebody's
apartment complex. I don't know, maybe I am pipe-dreaming again but I think
the this is very do-able. What do you think??
********************************************Michael S. King
********************************************Seism0man@....... (with a zero)
********************************************Santa Cruz, CA
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Seism0man@.......
Subject: Re: jelly bean seismology
Date: Thu, 8 May 1997 23:49:33 -0400 (EDT)
Hi,
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: New seismometer
Date: Thu, 08 May 1997 21:32:42 -0700
Aart Olsen wrote:
>
> Well "no moving parts" isn't a big deal. Force-balancing accelerometers
> generally have no moving parts -- that's the whole idea: f-f=ma=0. The
> three axis seismometer I'm building uses a bowling ball rigidly held in a
> plywood box, with piezo film sensors at the six contact points.
>
At one time I made a sensor composed of 6 orthogonal tubes (kids jack
looking). They were all connected in the center with a reservoir. At the
end of each tube was a peizo disk. I then filled the whole thing with
mineral oil. I summed "in line sensors" to get three component data.
I had problems getting anything. I think the gain was to low. It seemed
like it should work.
Barry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Charles R. Patton" <patton@.........>
Subject: Re: Sensitivity required of seismometers (Re: Humphrey Accelerometer)
Date: Thu, 08 May 1997 22:36:24 -0700
A couple of people were asking about sensitivity of the Humphrey
accelerometer for seismometry, so I decided to post the collection of
snippets of PSN conversations which I think shows the relative range one
needs for a resonable, ambient noise limited unit. On the basis of
these comments, I think our Humphery based unit is going to be in the
ball park. Additional comments, clarifications and corrections on my
interpretation would be more than appreciated.
Thanks,
Charles R. Patton, editor, Geo-Monitor
paton@.........
****
Compilation of anecdotal notes
on sensitivity from PSN discussions. 5/7/97
****
In particular notice comment of 3/11/97. From some of the other
discussions, I think Larry means the unit has 16 bits, but he removes 4
bits due to the local ambient noise floor. All the comments taken
together, indicate ranges from 2^12 to 2^21+. My guess is that ambient
generally tends to dominate above 2^16 (with a +-2 g max range.) So the
Humphrey works out to +-2^16 which is probably adequate for all but the
quietest rural sitings.
---------------1/2/97------------------------
Karl Cunningham
My current breadboard has a full-scale (20 V) output for about a 0.004"
movement or so. I'd like to get to a signal-to-noise ration of 16 bits,
with a noise floor of 10 nanometers or less. Right now I'm at about
40-50 nm.
---------------1/31/97-------------------------
Larry Cochrane
I routinely receive M7.0 10,000km with both
my Lehman and even better with my SG sensor. Local ground noise tends to
be
pretty high frequency compared to the low frequencies involved in
teleseismic events. So it is possible to receive teleseismic events even
if you live near a lot of local ground noise. The SG sensor has a poor
response above 1 hz so it does a good job at filtering out the ground
noise. With a Lehman you can run the signal thru a low low-pass filter
say .5 seconds (or lower) that will remove a lot of the high freq noise,
or, you can use WinQuake and filter the event file using the FFT /
filtering feature.
--------------2/4/97------------------
It looks like up north is rocking and rolling. We just had 2 events near
Santa Rose California. The first was 3.4 MD followed by a 3.8MD about 40
minutes later. Here are the numbers from finger quake@...............
97/02/04 23:45:45 38.36N 122.65W 5.9 3.4MD B* 3 mi ENE of Rohnert
Park,CA
97/02/05 00:25:41 38.36N 122.65W 6.3 3.8MD B* 3 mi ENE of Rohnert
Park,CA
The events are about 100km (64mi) from me.
I have a new sensor that I am monitoring. I was able to barrow a Forced-
Balance Accelerometer from the local USGS (thanks to Ed C. help). It's a
Kinematics FBA 23 with an output of +-10 volts for a +-2 G input. I
currently have one channel (N-S orientation) connected to one of my 16
bit A/D cards. It's producing *.LC5 files on my system. The output of
the
sensor is DC and goes directly into the A/D card with no filtering or
gain
change except a divide by 2 so the +-10 output matches the +- 5 volt
input of
the A/D card. I will be adding more channels (the sensor has 3 axis),
low-pass filtering and AC coupling when I get some time.
The FBA sensor did not go out of the normal background noise, about 20
counts P-P or about 1.2 mG [(4G's / 65000 counts) * 20 counts]. I think
the 3.8MD just broke the background noise.
------------------------1/28/97-----------------
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
However, this scheme requires an
accelerometer with a range of at least 10**-6 at the low end to about
2.0 g at the high end. This corresponds to a dynamic range of about 130
dB or 21-22 bits of resolution.
------------------3/11/97---------------------
Larry Cochrane
At 09:01 AM 3/11/97 -0600, you wrote:
>I noticed they Coyoty Point USGS sensor was saturated! You can
>tell it's digitized to 12 bits because +-2048 was as large as the
>numbers went.
The telemetry system only has a dynamic range of a 12 bit system. I
remove
the lower 4 bits because they only contain noise.
>
>Larry I noticed that good old .LC1 just barely saturated at +32767.
>
All of my other sensor have the full 16 bit data saved.
------------------3/16/97------------------------
Larry Cochrane
I have the gain set
so it has a +- 2G full scale output. This is the same as my (it actually
belongs to the USGS) commercial Force Balanced Accelerometer I have
online.
....Compared to the commercial FBA (again
both set to ~+-2G) the ADX05 sensor has about 15x more background noise.
The
FBA sensor does not pickup any local ground noise either, so all of the
noise is inside the ADX05 chips. Unlike the ADX05 sensor the FBA has
almost
no output when it's just sitting there. If definitely has a high dynamic
range.
-------------------3/17/97------------------------
Larry Cochrane
Now for the counts. First remember that the ML scale is based on the
power
of 10 and it measures maximum amplitude (or max A/D counts). If you had
a
sensor that produces a max peek count of say 500 for a ML3.0 100km away
then
a ML4.0, at the same distance, would produce a max count of 5000
(saturating
a 12 bit system0 and a ML5.0 would produce 50K counts saturating a 16
bit
system). I don't have any numbers for how the distance changes things.
You
can play around with WinQuake and see for your self how distance effects
the
numbers.
Some real numbers, the two ML3.6's a few days ago just saturated my
Lehman. The event was 37 km or 23 miles away. If my calculations are
right then
the coil produced a maximum output voltage of ~3.0mv for this event. A
ML3.2
event (one at the Geysers up north from me) ~150km (94mi) away produced
a
max count of 2215 or .0002 mv at the coil. For teleseismic events I look
at
a resent 6.8 in Mexico, about 2900km (1800mi) away, produced a max count
of
around 2600, very close to the local ML3.2 event.
-------------------------3/22/97------------------------------
Larry Cochrane
As you know I have been asking about G forces relating to strong motion
sensors. The ML4.4 Hollister event last night was picked up on the
Kinetics FBA-31 sensor I have. The max +- A/D counts where only 41. This
works
out to +- .0025 (2.5mG) of acceleration. You can check out the event
file
yourself by downloading the following file: 970322a.lc5. The P wave was
just out
of the background noise level, but the S can be clearly seen.
-------------------- ~ 4/16/97---------------
Jim Hannon
...........the PEPP seismograph has a spec of 100 nm/sec (velocity) for
instrument noise..........
-----------------------------4/29/97------------------
rc baker
The instruments resolve ground noise at least from a 0.3 to
300-sec period (typically from 0.1 to 3000 sec) and have a dynamic range
of 140 dB... (7; p 2349).
--------------------------------5/1/97--------------------
CRANSWICK@........
The network needs an inexpensive, reliable, standardized and
mass-produced seismograph: the digital seismological equivalent of a
Sony Walkman. It must be able to record three components of ground
acceleration with a dynamic range of 0.00001-1.0 g in the frequency band
0.1-20.0 Hz and maintain absolute time to a precision of 5 ms. Typical
records would be sampled at 50 sps/component and have a duration of
30-300 s.
---------------------------5/6/97-------------------------
Bob Barnes
Aki & Richards, "Quant. Seismology" vol 1 p 494 sez that a M6 quake at
a distance of 80 deg would have Rayleigh wave (with a period of 20", the
period of minimum attenuation) accelerations of 10e-7 g. The really
interesting phases, P & S, are usually much smaller--perhaps 10e-8 g.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Tim Brockwell <bwell@..........>
Subject: Tornado - Coincident Seismic or Acoustic Data
Date: Sat, 10 May 1997 01:51:30 -0500
Does anyone out there know where I can find archives of seismic or
acoustic data that were collected just prior to or during tornadic
activity?
Thanks Much in advance,
Tim
--
-------------------------------------------------
- Tim Brockwell -
- Lockheed Martin Missiles and Space Company -
- Ph: (205) 722-4080 Fax: (205) 722-4251 -
- bwell@.......... -
-------------------------------------------------
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ABdikjse@.......
Subject: Re: Tornado - Coincident Seismic or Acoustic Data
Date: Sat, 10 May 1997 03:12:52 -0400 (EDT)
I don't know if this can help you... many others on PSN can probably steer
you more clearly. You might want to try the ftp below for seismic
information:
ftp scec.gps.caltech.edu
There are seismic archives there although you'll have to rout through some of
the posts a bit to find exactly what you want
Good luck.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jean-Jacques HUNSINGER <jjh@............>
Subject: nice event
Date: Sat, 10 May 1997 10:45:14 +0200
hi all !
i'm receiving a large event here in france. Begining at 8h17 UTC.
delay between P and S waves : 17 mn.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: nice event
Date: Sat, 10 May 1997 21:19:34 +1200
Jean-Jacques
nothing on the USGS site as yet I presume it was for 10 05 97 0817 UTC
you didnt state a day.
BTW did you recieve my last post to you a few days ago ???
Dave N.
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: nice event
Date: Sat, 10 May 1997 21:22:22 +1200
Jean-Jacques
further to my previous post i checked the heli corder in reno,
University of Nevada USA
It shows a bigggg event!!
Dave
At 10:45 AM 5/10/97 +0200, you wrote:
>hi all !
>
>i'm receiving a large event here in france. Begining at 8h17 UTC.
>delay between P and S waves : 17 mn.
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: nice event
Date: Sat, 10 May 1997 01:22:54 -0700
Hi,
If my P and S picks are right it looks like it's about ~8200km from my
station. I'm getting a magnitude of around 6.7.
Jean-Jacques, I think this is your first post to the group and I don't see
your station information on the PSN map. Can you tell use more about your
station?
Regards,
Larry Cochrane
Redwood City, PSN
At 10:45 AM 5/10/97 +0200, you wrote:
>hi all !
>
>i'm receiving a large event here in france. Begining at 8h17 UTC.
>delay between P and S waves : 17 mn.
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: nice event
Date: Sat, 10 May 1997 21:32:10 +1200
Gidday Larry
I'm already working on him for the data Just waiting for him to send it
to me
Dave
At 01:22 AM 5/10/97 -0700, you wrote:
>Hi,
>
>If my P and S picks are right it looks like it's about ~8200km from my
>station. I'm getting a magnitude of around 6.7.
>
>Jean-Jacques, I think this is your first post to the group and I don't see
>your station information on the PSN map. Can you tell use more about your
>station?
>
>Regards,
>Larry Cochrane
>Redwood City, PSN
>
>>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: location now
Date: Sat, 10 May 1997 21:49:40 +1200
hi all,
hot from the USGS
97/05/10 07:57:32 33.65N 59.74E 33.0 7.3Ms A NORTHERN IRAN
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: nice event
Date: Sat, 10 May 1997 13:27:09 -0700
At 01:22 AM 5/10/97 -0700, I wrote:
>
>Hi,
>
>If my P and S picks are right it looks like it's about ~8200km from my
>station. I'm getting a magnitude of around 6.7.
Well I blew this one. The event was a lot bigger and farther away. I should
have known this because the USGS sensors I monitor did not pickup the P
wave like they normally do for large teleseismic events. O well, live and
learn....
-Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Sensitivity required of seismometers (Re: Humphrey
Date: Sat, 10 May 1997 13:46:04 -0700
At 10:36 PM 5/8/97 -0700, Charles R. Patton wrote:
>
> In particular notice comment of 3/11/97. From some of the other
>discussions, I think Larry means the unit has 16 bits, but he removes 4
>bits due to the local ambient noise floor. All the comments taken
>together, indicate ranges from 2^12 to 2^21+. My guess is that ambient
>generally tends to dominate above 2^16 (with a +-2 g max range.) So the
>Humphrey works out to +-2^16 which is probably adequate for all but the
>quietest rural sitings.
>>------------------3/11/97---------------------
>Larry Cochrane
>At 09:01 AM 3/11/97 -0600, you wrote:
>>I noticed they Coyoty Point USGS sensor was saturated! You can
>>tell it's digitized to 12 bits because +-2048 was as large as the
>>numbers went.
>
>The telemetry system only has a dynamic range of a 12 bit system. I
>remove
>the lower 4 bits because they only contain noise.
>
12 bits is right. The USGS analog tone system does not have more then 12
bits of dynamic range. They only use 12 bits to record the data. The
limited dynamic range (not that 12 bits is that bad) is do too the limited
bandwidth, +-125 hz deviation for each sensor channel (each audio channel
can have up to 8 sensor channels) and general radio noise.
-Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Can you help on this?
Date: Mon, 12 May 1997 15:20:38 -0600
Aaron-
There is an international group of amateur seismologists (most of whom
live in California), the Public Seismic Network, who record earthquakes
with their own seismographs and exchange the digital waveforms they
record. You should look at the websites,
http://psn.quake.net/
and
http://www.pacificnet.net/~darby/index.html
for information about making and/or obtaining and operating your own
seismograph. There are at least six PSN stations in Southern California
(see http://psn.quake.net/dave/map.htm ).
Please let me know if I can be of further assistance.
-Edward
mori@...................... wrote:
>
> From: SMTP%"mjackson@......................" 6-MAY-1997 07:42:30.22
> To: AResella@.......
> CC:
> Subj: Re: seismometer for the home
>
> Dear Aaron,
>
> Thank you for using the Ask-A-Geologist Program. You are asking for some
> very interesting questions. However, I live in Fairbanks, Alaska and
> work as a hydrologist rather than a seismologist. I have forwarded your
> questions to a gentleman in Pasadena. His name is Jim Mori. He has
> been very helpful in the past regarding earthquake questions. Below is
> his mailing address, phone number, and email address. I think that Jim
> will be able to help you with anything you may need. He also works with
> the US Geological Survey and can talk to you about volunteering at a
> nearby office.
>
> ----------
> James Mori
> 818-405-7821
> 525 Wilson St. (Mailing Address)
> Pasadena, CA 91125
>
> Cal Tech, Room 001 (Office location)
>
> mori@........ or mori@......................
> ----------
>
> Once again, thank you for using Ask-A-Geologist program. If you have
> any problems or more questions, please feel free to contact me.
>
> Melanie Jackson (mjackson@.........
>
> ************************************************************************
> On Mon, 5 May 1997 01:59:05 -0400 (EDT)
> AResella@....... said:
> > My is Aaron, I'd like to know if can purchase a seisometer for my home,
> > ethier a mechanical thats relatively sensitive, or one I can hook-up to my
> > computer. I live in Santa Clarita Valley, we've been having many quakes
> > here,
> > especially around the Newhall and Castiac Area, I read your latest
> > earthquake
> > event for southern california, I love it !!!, Is their a nice color map of
> > Los Angeles
> > showing all the faults? and where can I get one?. I'd also like to see if
> > can do
> > voulunteer work in my area for the USGS. and can I get newsletters from the
> > USGS? Well thanks,
> >
> > Aaron Resella
> > 26103 Mc Bean Parkway #132
> > Valencia, CA 91355
> >
> > E-mail addr.: aaron@.......
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: [Fwd: Re: New RT website]
Date: Mon, 12 May 1997 15:46:59 -0600
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
From: Edward Cranswick <cranswick@........>
Subject: [Fwd: New RT website]
Date: Mon, 12 May 1997 15:46:35 -0600
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
From: Jean-Jacques HUNSINGER <jjh@............>
Subject: small event
Date: Tue, 13 May 1997 08:49:23 +0200
hello,
just recording an event starting 13 Mai 97 at 6h25 UTC.
seems to be only surface waves.
wating for more infos...
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: latest addition to map
Date: Tue, 13 May 1997 22:36:01 +1200
hi all,
well it has been a while but it was worth the wait. We have a
new member and country to add to the group who has also submitted the info
to be added to the PSN map
Welcome to Jean-Jacques Hunsinger from Badevel near the town of
MONTBELIARD, France
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: another new listing
Date: Wed, 14 May 1997 19:51:50 +1200
greetings all,
Please extend a warm welcome to Ron Westfall of Nth
Vancouver, BC., Canada
He has been on the mailing list for a wee while but is now logged on the
database and PSN map
Dave
PS the Hale-Bopp comet is looking good above the north-western horizon
after sunset
it is naked eye visible from ~1800 hrs NZST (0600 hrs UTC) at 7 deg
above the horizon and is setting ~1855 hs NZST
in my 10" f 4.5 Meade reflector scope it is sporting a broad fan shaped
tail, one side of which is extending some 3 - 4 deg's.
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Kenneth.DeNault@.......
Subject: Seismographs
Date: Wed, 14 May 1997 09:41:22 -0500 (CDT)
Greetings all,
I am looking for any information on commercially available, inexpensive,
refraction seismographs that would be sutibale for use in a Physical Geology
(General Education Course) and Structural Geology course. Any information
would be greatly appreciated.
Thanks,
Ken De Nault
DENAULT@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: [Fwd: PSN info]
Date: Wed, 14 May 1997 12:17:39 -0600
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
From: Edward Cranswick <cranswick@........>
Subject: [Fwd: High-frequency resonances of broad-band installations]
Date: Wed, 14 May 1997 12:34:19 -0600
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
Bob-
I was impressed by the very thorough installation procedures that you
describe at this website,
http://www.seismo.berkeley.edu/seismo/bdsn/instrumentation/guidelines.html
..
The frequency band you are concerned about, 7-1000 s, is far away from
my experience, and I was wondering whether you are concerned with
high-frequency (1-50 Hz) sensor/site resonances? In my experience,
seismic piers and the legs of seismometers that are designed to minimize
low-frequency noise can produce very severe resonances in the
high-frequency band that significantly degrade data quality. So do you
anticipate that these might be a problem for your monitoring of local
events?
-Edward
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
From: Edward Cranswick <cranswick@........>
Subject: Comment on: PSN info
Date: Wed, 14 May 1997 12:36:44 -0600
PSN-
I have just forwarded the website of a description of the very thorough
broad-band seismometer installation done by UC Berkeley. The
installation focuses on deploying the instruent at an optimal site and
insulating the instrument from local effects. Designed to study source
and regional seismic phenomena, it is a good example of the type of
installation that will NOT monitor the ground motions where most people
live.
-Edward
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: Seismographs
Date: Wed, 14 May 1997 15:59:35 -0800
Ken,
This page gives a possible source for some inexpensive (or free)
refraction geophones:
http://www.giseis.alaska.edu/Input/lahr/web.sites.html#GEOPHONES
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Rev. Bob Shannon" <rshannon@.......>
Subject: Re: Seismographs
Date: Wed, 14 May 1997 17:38:52 -0700 (PDT)
I wonder if I could impose my own web page. I have been a member of this
list without much comment for quite a while...and I also realize that most
of you folks are in the scientific community of which I normally from much
respect.....
I have been doing my own personsal research into alternative methods of
predicting EQ's for many years. I am very opinionated to the point of
boredom for some researchers:-> but I continue on....So if your heart is
into the unusual or unexplained, then please visit me at my web site, and
let me know what your impressions are! I am willing to take the jabs and
barbs...I am quite used to it! I also very much respect your many years of
work! Collectively speaking:->
Bob
http://iea.com/~rshannon
Thanks and Bless
Rev. Robert Shannon Sr. Hon. DD Theology
Pinpoint Newsletter
"The web existed before spiders. The web existed before the net...
We are all a part of the web and whatever we do to part - we
do to the whole"
------------------------------------------------------------------
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: TESMECO@.......
Subject: Re: [Fwd: PSN info]
Date: Wed, 14 May 1997 21:56:59 -0400 (EDT)
couldnt we aolers , drag our favroite place to the mail then just click on it
for new sites <A HREF="http://psn.quake.net/">Redwood City Public Seismic Net
work</A> lets see if it works
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: AURORA ALERT!!!!!!!
Date: Thu, 15 May 1997 19:02:46 +1200
HI all,
for all of you who also look up there is a bright green
aurora visible
bob hammond and the guys in Nthrn USA and canada get out of thet arm
chair and get outside hopefully the coming summer sky isnt too bright...
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm ( world wide access )
When The Last Of Ten Screws Has Been Removed From A Cover,
It Will Be Discovered That The Wrong Cover Has Been Removed
When The Last Of Ten Screws Has Been fitted back Into A Cover,
It Will Be Discovered That The gasket Has Been Left Out
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Benjamin Boozer <bbb3@..............>
Subject: Microbarographs and HETs
Date: Thu, 15 May 1997 08:33:32 -0400
Recent talk of homebrew micromanometers has given me the incentive to
complete a microbarograph of my own based on a Hall Effect Transducers an=
d
a speaker cone. The basic principle of operation is as follows. One side =
of
a vertically oriented 8" woofer (magnet basket removed) is connected to a=
reference air volume (12 gal. air tank) with the other side exposed to th=
e
atmosphere. the speaker cone is mounted to the underside of a board. The
board has a hole cut in the center through which a small rod is placed. T=
he
rod is in contact with the center of the speaker cone and sticks out of t=
he
top of the mounting board. As the air pressure changes, the rod moves up
and down. Mounted flat on top of the rod is a small rare earth magnet
(Radio Shack). A Hall Effect Transducer is mounted nearby (approx. 2mm
away) so that the magnet can move parallel to the sensing element. With t=
he
air tank disconnected, the HET is adjusted up or down so that its output=
voltage is 1/2 the supply. That indicates that the magnet is positioned i=
n
the center of the HET with its magnetic field essentially nulled. Movemen=
t
up or down caused by air pressure will move the magnet creating the outpu=
t
signal.
The device is very sensitive. While in the den, I was able to detect air
pressure changes caused by pressing my hand on a wall. Any doors opened =
or
closed are easily detected.
My goal is to be able to detect atmospheric disturbances caused by natura=
l
events, mabye an earthquake or volcano. I would appreciate any help from
someone who could point me in the direction of determining the propagatio=
n
rate of such an event through the atmosphere.
This group has taught me more than I could have ever dreamed.
Ben Boozer
=
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Benjamin Boozer <bbb3@..............>
Subject: Microbarographs and HETs
Date: Thu, 15 May 1997 12:10:00 -0400
My first attempt at sending this appears to have been corrupted. Sorry. I=
have =
constructed a microbarograph based on a speaker cone and a Hall Effect
Transducer. The device is sensitive enough to detect air pressure changes=
in my house caused by pushing my hand on a wall or swinging any of the do=
ors.
A woofer cone (minus the magnet basket) is mounted cone up. The lower sid=
e of
the cone is connected to a reference air mass (12 gal. air tank) with the=
upper
side to the atmosphere. A short rod is mounted above the center of the co=
ne such
that when the cone moves in or out, the rod moves up or down. A rare eart=
h magnet
is mounted on the top of the rod. It moves past a Hall Effect Transducer =
mounted =
parallel to the rod. The HET is adjusted up or down so that at rest, the =
magnet is
centered on the HET creating an output voltage one half the input. Any va=
riation in
air pressure causes the magnet to move up or down past the face of the HE=
T, =
changing the output voltage.
My goal is to be able to detect atmospheric variations caused by natural =
disturbances
such as an earthquake or volcanic eruption. Any information determining t=
he speed =
such disturbances could propagate through the atmosphere would be appreci=
ated.
Ben Boozer=
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Charles R. Patton" <patton@..........>
Subject: Comment on Berkeley "Installation Guidelines.."
Date: Thu, 15 May 1997 10:50:53 -0700
Bob,
Your "Guidelines for Installation..." web page
<http://www.seismo.berkeley.edu/seismo/bdsn/instrumentation/guidelines.html>
is very appreciated. It provide useful hints to high quality
installations.
In the interest of being able to compare our amateur installation re-
sults, it would be helpful if in Figs. 3 and 4 you would indicate what
the PSD units are -- g or displacement and perhaps a simple explana-
tion of PSD since I would of thought the measurement would be :
g / Hz^0.5 or d / Hz^0.5
as for instance op-amp specs would use:
v / Hz^0.5 not power per root Hz.
And again in a similar vein, a rough calibration of counts and in what
units (g or displacement) on the Y axis of Figs. 7 and 11.
Thanks,
Charles R. Patton <patton@..........>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Michael Chang <pya_cha@..................>
Subject: Re: Microbarographs and HETs
Date: Thu, 15 May 1997 14:49:22 -0700
At 08:33 AM 5/15/97 -0400, you wrote:
>Recent talk of homebrew micromanometers has given me the incentive to
>complete a microbarograph of my own based on a Hall Effect Transducers and
>a speaker cone. The basic principle of operation is as follows. One side of
>a vertically oriented 8" woofer (magnet basket removed) is connected to a
>reference air volume (12 gal. air tank) with the other side exposed to the
>atmosphere. the speaker cone is mounted to the underside of a board. The
>board has a hole cut in the center through which a small rod is placed. The
>rod is in contact with the center of the speaker cone and sticks out of the
>top of the mounting board. As the air pressure changes, the rod moves up
>and down. Mounted flat on top of the rod is a small rare earth magnet
>(Radio Shack). A Hall Effect Transducer is mounted nearby (approx. 2mm
>away) so that the magnet can move parallel to the sensing element. With the
>air tank disconnected, the HET is adjusted up or down so that its output
>voltage is 1/2 the supply. That indicates that the magnet is positioned in
>the center of the HET with its magnetic field essentially nulled. Movement
>up or down caused by air pressure will move the magnet creating the output
>signal.
>
>The device is very sensitive. While in the den, I was able to detect air
>pressure changes caused by pressing my hand on a wall. Any doors opened or
>closed are easily detected.
>
>My goal is to be able to detect atmospheric disturbances caused by natural
>events, mabye an earthquake or volcano. I would appreciate any help from
>someone who could point me in the direction of determining the propagation
>rate of such an event through the atmosphere.
>
>This group has taught me more than I could have ever dreamed.
>
>Ben Boozer
Interesting exercise Ben. Without knowing details of the nature of
atmospheric disturbances caused by natural events, it would appear to me
that your setup will behave as an uncalibrated detector over some narrow
band in the infrasonic range. My first thoughts from reading your setup led
me to my not-yet-constructed homebrew micromanometer using a similar
scheme, but using the high compliance woofer's voice coil as a sensor,
coupled to a dual semi-integrator to compensate for losses from it's
operation in the compliance controled region. This scheme should result in
an essentially flat response from the turn-over frequency of the dual
semi-integrator (set to some mHz region) up to the speaker/box resonnance
(typically around 80Hz). An air tight enclosure housing the speaker would
natually be required. System dynamic range would be limited by the
excursion limits of the woofer (typically +/- 5mm).
I appreciate reading regular contributor's correspondance, but have never
participated because I'm not a particularly good writter, and have a rather
limited knowledge of seismology. But none the less, wish to say thanks for
all i've learned.
Some time in the future, when I'm prepared, I'll share my exercise of a
small seismic sensor using a discarded Thoren's phonograph tone arm, with a
magnetic cartridge as a 2 axis sensor, using negative impedance
compensation to flatten response down to near DC.
Michael Chang Montreal, Canada
("`-''-/").___..--''"`-._
`6_ 6 ) `-. ( ).`-.__.`)
(_Y_.)' ._ ) `._ `. ``-..-'
_..`--'_..-_/ /--'_.' ,'
(il),-'' (li),' ((!.-'
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: roger baker <rcbaker@........>
Subject: Re: Microbarographs and HETs
Date: Thu, 15 May 1997 17:14:09 -0500 (CDT)
Friends,
My first reaction to the recent post is that the instrument
described might appear to be sensitive, but might not be so because the
displacement is integrated over the large surface of a woofer cone.
I do not know the displacement sensitivity of hall transducer,
but I would imagine on the order of one micron. If we assume the
sealed air volume is 12 gallons and the woofer surface area is 12 inches,
this would be about 50,000 cc volume and roughly
1000 sq cm piston area. I would assume this would create about a 50x
magnification volume of the atmospheric pressure expansion on the speaker
cone if the cone were airtight, which most aren't I think.
Contrast this with the 4000 cc volume and 1 mm surface area of my
micromanometer, which would give a 400,000 times magnification of the
volumetric displacement of my sensor. Even if we assume that my optical
sensor is less sensitive by a factor of ten to displacement, it is still
airtight and has a controllable leak, which factors seem to determine
sensitivity in practice. I place my gallon glass jug in an insulated
cooler. The complete sensor costs only a few dollars. That said, the
biggest problem with my micromanometer and optical sensor is that it is
too sensitive and frequently goes out of range, when the bypass air leak
is made small. In fact when I connect it to an audio output and voltage
controlled oscillator, it is always growling and whistling in slowly
varying pitches and making briefs jumps in pitch for inexplicable but
probably genuine causes when it is not drifting out of its sensitive range.
My current thinking is that maybe some type of feedback
could be used to keep the sensor locked into a narrow range, but the
device itself is extremely cheap and sensitive and has no apparent
hysteresis. Its only defect is its tendency to go out of range and the
fact that it might need frequent adjustment for this reason and might be
temperature sensitive to some degree.
--Yours, Roger baker
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Brian Chesire <BCChesire@................>
Subject: Re: Microbarographs and HETs
Date: Thu, 15 May 1997 17:00:42 -0700
A recent article in 'Design News' mentioned the use of microbarographs
to count meteorite entrys in the atmosphere. I can't find the reference
now but will post it when I do. I beleive it was an NOAA project.
Brian
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Re: [Fwd: PSN info]
Date: 15 May 97 21:11:24 EDT
John,
Thanks for this URL--fascinating stuff!
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: PMD seismometers
Date: 15 May 97 21:11:20 EDT
Hi gang,
Bill Scolnik sent me a copy of data sheets on the PMD seismometers. These are
one of the sensors which the Princeton Earth Physics Project (PEPP) is using.
'Grams published by PEPP using the PMD look very good for teleseismic events.
The company is:PMD Scientific, Inc., 105F W. Dudleytown Rd., Bloomfield, CT
06002, 860-242-8177, pmdsci@................
PMD stands for Precision Measurement Devices. Their basic translational
model, Model 2023, is a 3-axis device in a round package 7" dia. X 4.6" hi
weighing 10 lbs. Freq. response is 0.033-5 Hz. The sensitivity is 1500Vsec/m
and need 12V at 12ma (that much I can afford). Their price is $2,800 but you
(if not an educational institution) have to buy them from Sprengnether Instr. ,
4150 Laclede Av., St. Louis, MO. I don't know what their price is.
PMD's 4-chan 22 bit (4.2 million counts !) PC plug-in board with software is
$1,100 but my guess is that any A/D will work because the output is +/- 5V.
Now it gets mysterious--"They are based on a pioneering 'molecular electronic
technology' and have no moving mechanical components." PEPP has described these
as 'electrolytic'. ???
I sent e-mail asking for a technical explanation of how it works. I'll pass
this along if it comes.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Tobin Fricke" <tobin@............>
Subject: Re: AURORA ALERT!!!!!!!
Date: Thu, 15 May 1997 18:59:52 -0700
> HI all,
>
> for all of you who also look up there is a bright
green
> aurora visible
What areas of the United States is this visible from, what area of the sky
is it in, and is it still visible?
Tobin Fricke
tobin@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert Avakian <ravakian@............>
Subject: Re: Seismographs
Date: Thu, 15 May 1997 16:21:18 -0700
Kenneth.DeNault@....... wrote:
>
> Greetings all,
>
> I am looking for any information on commercially available, inexpensive,
> refraction seismographs that would be sutibale for use in a Physical Geology
> (General Education Course) and Structural Geology course. Any information
> would be greatly appreciated.
>
> Thanks,
>
> Ken De Nault
> DENAULT@.......
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
If you can afford to rent a system for a few days, try Geometeics in
Sunnyvale, CA. They were very helpful in helping me when I wanteed that
and a magnetic system for my class this year. If you E-mail me directly
I can provide you with a contact name.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: shansen@........ (shansen)
Subject: Microbarographs
Date: Fri, 16 May 1997 19:51:06 -0400 (EDT)
It's nice to see the interest in microbarographs. For those new to the list,
you might check the archives starting about last June when I started a string
on the subject. A complete article on my instrument, based on a differential
capacitance manometer, may be found listed at
http://www.tiac.net/users/shansen/belljar/articles/htm. From that directory
click on the last article. There are also a number of good references concerning
infrasound generated by bolides, volcanos, nuclear weapons, etc.
Steve Hansen
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Toward a jellybean seismometer
Date: Mon, 19 May 1997 21:47:56 -0600
Wayne-
Sorry it's taken me so long to reply, but with respect to your idea
about the 150' well casing acting as an antenna, as a general rule, the
less crap you have between your sensor and the Earth, the better. The
"antenna" might pick up a bunch of seismic noise in addition to your
source, and/or it also might distort the source signal. Putting the
sensor 150' downhole is one of the best ways to get your sensor close to
the Earth and reduce noise from surface sources (but that's not feasible
for a long-period Lehman, though many borehole seismometers have been
manufactured for that purpose).
-Edward
Wayne H. Francis wrote:
>
> Edward Cranswick wrote:
> >
> > Roger-
> > That is a very interesting summary of modern seismic sensor design that
> > you presented. I have never been very involved with the nitty-gritty of
> > sensor hardware design, so it illuminated some issues, such as the
> > relationship between sensitivity and Q, about which I had previously
> > heard but passed over without much thought. I discussed some of my
> > larger concerns in the "Recording Ground Motions Where People Live"
> > article that I posted this morning, but I will comment about a few
> > specific issues in your summary below:
> >
> > roger baker wrote:
> >
> > > The most favored locations for seismometers
> > > are on concrete piers or inside mines or in concrete enclosures, or best
> > > of all in deep bore holes (5; p 724-5).
> >
> > The depends upon whether you want to study the seismic source
> > (earthquake or explosion, chemical or nuclear) or the hazardous effects
> > of ground shaking. Only the PSN is recording ground motions in the
> > Santa Clara Valley where over a million people of the San Francisco Bay
> > Area live; the USGS seismographs in the area are at "favored locations"
> > (according to the above) in the hills where few people live.
>
> > <snip>
>
> > --
> > Edward Cranswick Tel: 303-273-8609
> > US Geological Survey, MS 966 Fax: 303-273-8600
> > 1711 Illinois St cranswick@........
> > Golden, CO 80401 USA E.M. Forster said, "Only connect".
>
> <snip>
>
> This brings me back to a question I posed to the group back during
> the Christmas holidays and to which I never got an answer:
>
> When I finally get a seismometer built (thanks to the wealth of
> info in this group) I had intended to install it in my pumphouse -
> concrete slab, 150 foot well with 11 inch steel casing down through the
> middle. As a novice to seismo stuff, I don't know whether this is a
> very good idea (with a 150 foot earth antenna, so to speak), or a very
> bad idea because of whatever noise at whatever frequencies may be
> occurring (the well is running artesian right now). The pump would run
> very infrequently...haven't operated it for a coupla years.
> (Interestingly, the well is part of my EQ preparedness program...guess
> I'll turn the well on and the seismometer off after the big one hits).
> If it's an unknown, I'm willing to experiment to see what the effect is,
> but if somebody already knows I'd appreciate the wisdom of the list so I
> can plan the relocation. Thanks in advance. Wayne
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: R7Giovanni@....... (by way of Larry Cochrane <cochrane@..............>)
Subject: seismograph
Date: Mon, 19 May 1997 22:53:00 -0700
I received this today. If anyone is interested please contact Robert
directly since he is not on the list.
-Larry
Hello.
I buy lots of computer and electronic test equipment at government
auctions. I just brought home a bunch of equipment today and found to my
surprise that I have purchased a (Ground water geophysical survey system)
Terraloc Mk 3 24 channel Seismograph. I guess ABEM (sweeden) makes it.
I also have an ABEM Terrameter SAS 300B resistivity meter. Also, power
supplies, cables, printer, all in heavy duty (typical military) weatherproof
cases, two to be exact, (rather large) When I plugged in the 24 ch
seismograph, it works, and has current date and time, and says it's been in
use 56 hours. Just about enough to burn it in at the factory, I'm guessing.
All the cables are still in bags, software disks are in their cases, tools
and instruction books there, everything. If you know how I might go about
trying to find a buyer for this equipment, I'd be glad to pay a reasonable
finders fee. I don't need it. I will do some checking around on the net and
elsewhere, but I'd like to move it pretty soon, as I'm moving out of Florida
to Nebraska soon.
Please call me at 904-763-5930 if you would like any further info on it, or
if you or someone you know would be interested in it. Thanks. Robert
Goering
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Benjamin Boozer <bbb3@..............>
Subject: Microbarographs
Date: Tue, 20 May 1997 13:32:20 -0400
Many thanks for the feedback on microbarographs. While monitoring some
remarkably periodic infrasonic waves the other day (approx. 25sec. period,
cause unknown), I wondered how someone might determine how sensitive a
homebrew microbarograph was. Running thru my house swinging doors and
pushing on walls is one thing, but I would rather have a rough estimate of
the pressure difference caused by moving a door. The seismograph calibrator
discussed here was brilliant, anybody know of a microbarograph calibrator?
Ben Boozer
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: roger baker <rcbaker@........>
Subject: Re: Microbarographs
Date: Tue, 20 May 1997 14:33:03 -0500 (CDT)
Friends,
I have been neglecting seismometer design to try to explore
microbarometry a little more thoroughly. I don't have a web page. Here
is a more complete description than my last post, since there seems to be
interest in the topic and since sensors are so easily constructed.
Forgive the length and my occasional digressions.
--Yours, Roger Baker
An Inexpensive Microbarograph and Micromanometer
There are many reasons that one might want to accurately measure the
volume of a gas. One might choose to buy a silicon diaphragm pressure
sensor, but these have the disadvantage of being rather insensitive and
expensive. One might choose to buy or build a capacitor micrometer or
microphone. These are even more expensive or rather tricky to build,
although they can be quite stable and sensitive.
Or one can do it the easy way. Here is a relatively cheap easy way to
build a simple differential micromanometer for between $10 and $20 that
can be made sensitive to nanoliter changes in volume in a gas or liquid.
This allows one to build a variety of scientific instruments. Some
examples might be a tiltmeter, a carbon dioxide measuring device, a
microbarovariometer or microbarograph (essentially a detector for
subsonic air pressure fluctuations that can be used to detect nuclear and
chemical explosions as well as nearby weather disturbances). Other uses
for such a device might be an infrared thermometer, a flowmeter, a
micropipette calibrator, a tactile pressure sensor for a robot hand, as
well as many other kinds of instruments. Due to the easy compressibility
of gases, measuring either very slight pressure changes in the volume or
the pressure of a gas near atmospheric pressure amount to much the same
thing. Experience building such a sensor develops easily transferrable
skills useful for building many other types of sensitive instruments and
detectors requiring optical detection and electronic amplification.
In principle my instrument is easy to understand. In practice it is
equally simple and inexpensive to build. One simply creates a short
column of liquid in a glass tube about one millimeter in diameter and
then uses an optical detector made from an LED and photodiode clamped
around the tube to measure the movement of a drop of the colored liquid
due to differential gas pressure.
(Another similar option is to use the tube and a clear liquid as a fluid
filled prism to refract light into a detector. The most sensitive option
is probably to use the fluid meniscus at the end of a small tube as a
reflective mirror. Any slight movement of the fluid column in relation to
the rim of the tube would alter the curvature of the meniscus and thus
the focal point of a collimated beam of light reflected into a nearby
detector. A $25 red laser pointer could be used to test this idea. It is
probable that infrasound detectors based on such principles could be used
up into the bottom of the audio sound range. Here the engineering would
get more complicated. It might pay to review the literature on elephant
infrasound communication and their ear design to see to what degree their
ears function as exponential horns to match the impedance of infrasounds
to their ear canals.)
If one wants to build a micromanometer, one simply compares the gas
pressure at either end of the capillary tube. If one wants to construct a
microbarograph, one simply connects a gallon glass jug kept at a
reasonably constant temperature to one end of the tube. Since there are
constant changes in barometric pressure throughout the day much greater
than the one that one might want to detect, a microbarograph may be made
relatively insensitive to slow changes by connecting the reservoir to a
slow and adjustable bypass leak.
It is easy to calculate that since a gallon is about four liters, a
contraction in volume of one microbar or one part per million in
atmospheric pressure should cause a reduction in volume of about four
cubic millimeters, assuming no leak. Most microbarographs are sensitive
to one microbar with some said to be as sensitive as one one tenth of a
microbar. If we use a glass capillary tube with an internal cross section
of one millimeter, then it should be very easy to detect even a tenth of
a microbar diplacement of the fluid column by optical means according to
the following principles.
In fact, the resistance to motion of a column of liquid that wets a
uniform diameter tube is very nearly zero. (If the tube is non-uniform in
diameter, however, the surface tension of the liquid will tend to draw
the liquid toward the smaller end). This may be easily seen by very
slightly tilting a small tube such as a melting point capillary
containing a drop of water or alcohol and watching the motion under a
microscope. A variation of this principle is used in the spirit level.
Likewise gravity will tend to bring a column to rest in the lowest
portion of a tube. In a U-Tube of classic manometer configuration, both
branches of the column are vertical. If the tube is slightly curved or
bent at a slight angle, the small amount of work needed to raise the
column of liquid can be magnified along a much greater distance. The
effective sensitivity of the device to a differential pressure change may
thus be increased, in a fashion analogous to the effect of using a very
gently curved tube in a bubble level. (It should be noted that surface
tension tends to strongly compress a circular band of liquid at the edge
of the meniscus where the contact angle changes abruptly and the wetting
dynamics of this zone determines the speed of movement of the fluid
column. Pure water is much more sluggish than alcohol. Careful
investigation is bound to uncover some interesting physics.)
A sensitive barograph is said to be able to detect a pressure change
equal to about a .7 micron column of mercury equivalent. In practice, a
very simple optical arrangement can probably detect a movement in the
column of liquid of ten microns or less. Since the density of mercury is
about 13.5 times that of water, this would be equal to about a 10 micron
displacement of a vertical water column, but this could easily be
increased by using a gently sloping column as noted above. In this way it
may easily be made too sensitive to be very practical unless some sort of
feedback is used to keep it from drifting out of range; it may be
adjusted so that it is constantly drifting over a period of a few
seconds; practical experience will soon demand that the sensitivity be
reduced below that which can be rather easily achieved.
The upper frequency response of the instrument will also tend to be
limited in practice by the viscosity of the liquid. A long column or a
glycerine column will tend to give a slow response while a short column
of water, or better, alcohol will give a fast response, perhaps extending
into the audio range.
One measures the variation in light absorption caused by a slight
movement of the column in response to any slight change in external gas
pressure, causing it to intercept to a variable degree an optical light
beam transversing the tube. This is very small and cheap to set up and
the use of solid state optics makes it very sensitive. One can zero the
column in relation to the optical detectors by tilting the glass tube
very slightly so that one edge of the nearly horizontal fluid column
shifts position slightly due to the combination of the forces of surface
tension and gravity until it is properly positioned to partially
intersect the light beam. This principle may be understood by visualizing
a U-tube manometer slowly tilted onto its side. When the tube becomes
horizontal, the restoration force of gravity will become zero and the
sensitivity of the column to differential pressure will approach infinity.
I use two super-bright red LEDs from Radio Shack for less than $2 apiece
as both the detector and the emitter. These LEDs make wonderful emitter
and detector combinations since the red light is very bright and all
adjustments are easily made with the bright red light. The second LED
being used as a detector is operated in the zero bias voltage mode. In
other words, it is allowed to function like a tiny solar battery
short-circuited with an external resistor. A one meg resistor loads it
enough to make its output linear without reducing the output voltage too
much. Under these conditions, the second LED becomes a very linear red
light detector in its voltage output, which can be easily measured with
any of a number of high impedence voltmeter or op amp circuits.
A scrap of glass tubing, a little silicone rubber, a little glycerine or
water and blue food coloring and a few scraps of aluminum and a nut and
bolt comprise the sensor. A Pyrex melting point tube makes an excellent
uniform capillary of a suitable diameter for the fluid column. I make a
right angle bend and then mount this with sloping portion of the tube to
balance the column. The sensor looks at the change in position of the
sloping portion of the column. Two small aluminum plates holding the LED
and photodiode are clamped around the tube to hold it in place.
Everything may be tilted slightly to center the column.
Each LED has its focusing lens ground off flat and is then glued with
clear silicone rubber behind a small hole in the aluminum plate. The two
plates are bolted together so they grip the glass tube from opposite
sides. Silicone is used to make little indented pads on the aluminum
plates that cradle the small glass tube in the proper adjustable position
so that the light beam from the LEDs just intersects the edge of the blue
column of glycerine. The glass tube can be slid back and forth into just
the right position to halfway intercept the light beam.
The associated electronics can be nothing much more than a 324 op amp and
6-12VDC battery power supply. The output voltage of such a sensor can
easily be made to have a range of 100 to one up to tenths of a volt with
a slight movement of the blue liquid column past the hole in the aluminum
plate. This output is probably responsive to tens of nanoliters of
volumetric change at near atmospheric pressure.
One leg of the photodiode is attached to an artificial ground made from
two 10K resistors that split the battery power supply and a voltage
follower to buffer it. The other leg is buffered with a voltage follower.
A variable potentiometer and voltage follower is used to balance this
signal produced by the photodiode. After the photodiode and potentiometer
signals are buffered by voltage followers, the difference is multiplied
by a factor of a thousand with the fourth op amp on the 324 chip. This is
done by putting a 1 K resistor on the noninverting input and a 1 meg
resistor in the feedback loop, and about a .01 microfarad cap across the
latter for stability.
This output is fed into a voltage controlled oscillator to give an
audible signal of variable pitch. A voltage controlled oscillator from a
one dollar 4066 CMOS phase locked loop chip and small piezo speaker are
useful to give the experimenter an audible indication of small changes.
When I first built such a device, I found it interesting to use such a
setup to audibly monitor the frequent barometric pressure swings
associated with a passing storm front. I believe such a device could
probably be modified to total the number and intensity of changes in
atmospheric pressure to warn of nearby weather disturbances
I use a very slow air leak in parallel with my micromanometer and
attached them both to a large reservoir of air in the form of a one
gallon glass jug kept in an insulated Igloo cooler. In this way the
instrument responds to rapid external atmospheric pressure changes acting
on the air in the jug rather than on temperature changes that cause the
air in the jug to expand or contract. Roughly speaking, the device might
respond to pressure changes ranging from perhaps several fluctuations per
second to 10 minutes, whereas very gradual changes in absolute barometric
pressure are automatically eliminated by the slow bypass air leak.
Not having a two hole stopper handy, I drilled two holes in a small
aluminum plate and sealed this plate directly to the mouth of the jug
with silicone rubber. Then I sealed two short lengths of vinyl aquarium
tubing into two snug holes in the plate the plate with more silicone. One
of the tubes is attached to the micromanometer, which is clamped in an
adjustable tilt position nearby. Its vinyl tubing is heated carefully
above a small flame until it is soft enough to stretch and reduce its
diameter enough that when cut, it will fit snugly over the end of the
small Pyrex melting point capillary.
The other vinyl leak tube has a little piece of cotton or strip of paper
inserted in the end. It is then clamped shut with a bulldog paper clip so
that the cotton or paper prevents it from closing completely. This
generates the slow leak that allows the manometer to accomodate slow
changes in atmospheric pressure while retaining high sensitivity to rapid
fluctuations. Usually, one will probably want to remove the clip to
equalize the air pressure while the position of the fluid column is
adjusted so that it halfway intercepts the light beam for best
sensitivity. Then the potentiometer is adjusted to give a midrange audio
signal. Finally the clamp is applied to give the slow leak. This leak
will need to be adjusted so that the instrument is not easily thrown out
of range by pressure fluctuations while remaining sensitive enough to
sense slight changes. If everything is set up properly, the setup should
remain stable and sensitive for some hours. This is easily ascertained by
briefly releasing the bulldog clamp to see if the proper output tone from
the audio output is restored when the atmospheric pressure differential
disappears. It is sensitive enough to detect the slight pressure increase
resulting from someone walking through a doorway into a room containing
the device. The biggest drawback of my device is probably the tendency
for the fluid column to drift to either end of its range when the
instrument is set up for too high sensitivity. Frankly, I have not tried
to refine my device for unattended long term stability.
Another untested variation of the device with a very wide range and
relatively greater long term accuracy could use a feedback arrangement
without any leak. One could use a reversible micropump to pump just
enough air in or out of the reservoir to exactly restore the column to
its central balanced or zeroed position. Another faster feedback option
is to use a stepping motor mechanism from an old hard drive to tilt the
sensing column up or down and restore balance using gravity. It is likely
that the sensor is slightly temperature sensitive, and if so this could
be eliminated by maintaining the sensitive portion slightly above room
temperature with a thermostat and by using glycerine to essentially
eliminate any slow evaporation of the fluid column.
Once the mechanical elements are working properly, a chart recorder or
computer data link can be used for quantitiative work that monitors the
amplified output of the op amp directly. For about $125, one can get a
nice LCD digital multimeter from Radio Shack that includes the software
and a serial port connector to turn a PC into a chart recorder.
Meanwhile, the audio output may remain connected for easy monitoring of
instrument performance.
It is obvious that many sophisticated and sensitive instrument designs
can be based on the conversion of differential pressure on a small fluid
column into mechanical motion of the column. The mammalian ear is only
one example. For another more classical and instrumentally sophisticated
option to microbarometry using a capacitor microphone see Steve Hansens
Bell Jar web page (he has posted his design and comments on PSN).
One interesting application might be to study and locate infrasound
sources in urban areas. Other applications are to locate distant
explosions. Maybe infrasonic communication would be practical for someone
other than elephants. So far as the detection of infrasound is concerned,
it would be very useful to be able to compare the responses of an array
of microbarograph sensors a kilometer apart. Since sound pressure waves
move relatively slowly through air, triangulation of sources should not
take large arrays or very accurate timing. This has already been done
with useful results in determining the locations of large mining
explosions. For interesting discussion and details see: Construction of
Regional Ground Truth Data Bases using Seismic and Infrasound Data; by
Gordon Sorrells. (http:www. geology.smu.edu~bonner/acoustic.html).
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David Josephson <david@...............>
Subject: Re: Microbarographs
Date: Tue, 20 May 1997 13:12:39 -0700 (PDT)
On Tue, 20 May 1997, Benjamin Boozer wrote:
> Many thanks for the feedback on microbarographs. While monitoring some
> remarkably periodic infrasonic waves the other day (approx. 25sec. period,
> cause unknown), I wondered how someone might determine how sensitive a
> homebrew microbarograph was. Running thru my house swinging doors and
> pushing on walls is one thing, but I would rather have a rough estimate of
> the pressure difference caused by moving a door. The seismograph calibrator
> discussed here was brilliant, anybody know of a microbarograph calibrator?
Pistonphones are used for calibration of acoustical transducers,
and you can get excellent accuracy. All you need to do is change your
reference volume by a precise amount, and if you know the total volume you
can calculate the pressure difference. A very simple micropistonphone
can be made by running a metal rod in and out of your reference volume
through a reasonably tight slip fit. If the rod is given a reciprocating
motion by being driven from an off-center point on a wheel, you can
produce a precise and repeatable variation in volume and thus pressure.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: A significant earthquake has occurred..
Date: Wed, 21 May 1997 13:55:06 -0700
If you can read the attached Seismo-Watch E-mail Earthquake Alert
Bulletin, you may want to consider subscribing this fantastic service.
Click here for more information:
http://www.seismo-watch.com/EQSERVICES/AlertBulletins/E-Mail1.html
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:info@................
http://www.seismo-watch.com
From: David A Nelson <dann@........>
Subject: Another good vanuatu event
Date: Thu, 22 May 1997 10:10:13 +1200
hi all here is the info from Caltech
General region : VANUATU ISLANDS
surface waves (3.0,3.5,7,7.5 mHz)
Stations used : CHTO CTAO DAV KIP PAB SNZO
Origin time: 1997 141 14 10 28
Original location (lat,lon,depth) : -20.4000 169.100 80
Moment tensor (x1.e26 dyncm) :
Mrr : 0.085192 Mtt : -0.056808
Mff : -0.028385 Mrt : -0.068503
Mrf : -0.746746 Mtf : 0.869582
T-axis: moment= 1.171 plunge= 30.457 azimuth= 126.831
N-axis: moment= -0.043 plunge= 49.232 azimuth= 353.831
P-axis: moment= -1.129 plunge= 24.310 azimuth= 232.235
best double couple: Mo= 1.150(x1.e26 dyncm) Mw=6.6 tau= 5.8
nodal planes (strike/dip/slip): 271.62/ 49.49/ 5.08 178.32/ 86.14/139.38
Centroid location : -20.125 169.377 65.261
Centroid time : 6.787
Variance reduction (%) : 50
***********
****----o ****
***--------o ***
**---------- o **
**---------- o **
*------- oooooooooooooo *
*-- oooooo o -----oooooo- *
** oooo o-----------oooo--**
*ooo o--------------ooo-*
**o o----------------oo**
** o+-----------------**
** o------------------**
* o------------------*
** o-----------------**
* o----------T------*
* P o---------------*
** o-------------**
** o------------**
*** o---------***
**** o-----****
***********
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie & Terri Thompson <ct@.......>
Subject: Long period borhole seismometers & force feedback
Date: Wed, 21 May 1997 20:29:49 -0500
PSN Readers:
It seems to me that the long period borehole
seismometers must be of the "force feedback" type.
They are small units which fit down a 10" borehole
yet have periods as long as 100 seconds. I can
only assume that the force feedback technique
is exploited to achieve such long periods with
a small unit.
Am I correct in assuming that the small pendulum's
period is effectively "lengthened" by the use
of a high gain force feedback configuration?
If ANY pendulum is held at rest by force feedback
it would appear that the natural period of the
pendulum is insignificant.
This seems like a great way to save space!!
-Charlie Thompson
Buda, Texas
_ ________________________________________________ _
/ ) | | ( \
/ / | Charlie Thompson WB4HVD | \ \
_( (_ | _ e-mail: ct@....... _ | _) )_
(((\ \> |/ ) http://www.onr.com/user/ct/ct.html ( \| </ /)))
(\\\\ \_/ / Latitude 30.112 N \ \_/ ////)
\ / Longitude 97.891 W \ /
\ _/ Seismic Station .BUE \_ /
/ / |________________________________________________| \ \
/ / \ \
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Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Re: Long period borhole seismometers & force feedback
Date: Wed, 21 May 1997 22:19:12 -0700
Charlie --
You wrote:
>If ANY pendulum is held at rest by force feedback
>it would appear that the natural period of the
>pendulum is insignificant.
I'm certainly no expert, but this is my understanding of the matter ...
(if I'm off base, someone please let me know).
I agree that within limits, the natural period of a feedback-restored
pendulum is not significant. Any pendulum or mass-spring system has the
equivalent of a spring constant -- the restoring force for a certain
deflection. The force feedback system can be considered to also have the
equivalent of a spring constant -- the restoring force for a certain
deflection. The object of the design of the force feedback system is to be
sure its "spring constant" is higher (stiffer) than that of the mechanical
system without feedback (preferrably 10:1 or 100:1 higher or more,
depending on the accuracy required).
At frequencies above the natural period of the mechanical system, the
effect of the feedback coil on the deflection of the mass decreases at a
second-order rate, so maintaining the ratio of spring constants becomes
more difficult. At some point you give up, and call that the upper
frequency limit of the instrument.
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: roger baker <rcbaker@........>
Subject: Re: Long period borhole seismometers & force feedback
Date: Thu, 22 May 1997 00:39:13 -0500 (CDT)
Charlie,
yes, I think thats right from my recent review of the
literature. A long period system must either have a very long pendulum or
a very weak spring and large mass combination and neither options fit in
small packages. Force feedback is the way to go and also tends to eliminate
the need for exotic suspensions like the LaCoste.
The tradeoff is the system must have very low frictional losses which means
the system must have a high Q which means that the mass must be 100 g or
more in air because of viscous damping. But 100 g ain't too bad and this
might be reduced further with a vacuum system (or helium) plus careful
design, but nobody has tried. Some of this was in the review I posted a few
weeks back.
--Yours, Roger
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Public Seismic Network Mailing List (PSN-L)
From: Benjamin Boozer <bbb3@..............>
Subject: Re: Microbarographs
Date: Thu, 22 May 1997 09:33:54 -0400
Thanks for the post on pistonphones. As a quick and dirty check I
constructed a small chamber for pvc pipe through which I threaded a 1inch
1/4-20 thumbscrew. A turn of the screw would move it in or out of the
chamber, changing the reference volume. According from the info in the post
from Roger Baker (thanks), a 12 gal. reference has to change by about 48
cubic millimeters to create a one microbar change in air pressure. With the
amp set for a gain of 10x, a 1.5 mm change in the length of the screw
caused a 0.1v swing at the output. With an approx. screw diameter of 5.56mm
and height of 1.5mm, the reference volume changed by 36 cubic millimeters.
That works out to about a 0.75 microbar change, not bad! (If my math is
bad, someone please correct me)
I have a large container (soon to be insulated) which will hold the entire
device and reference. As far as frequency response goes, the upper limit
appears to be around 3-4hz. with the lower end below 0.01hz. I am going to
experiment with porous "soaker" hose on the input to reduce noise.
Benjamin Boozer
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Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Unreported Events
Date: Thu, 22 May 1997 09:08:01 -0700
Hi all --
In addition to the Guerrero event, my FB also recorded five other >3 events
today (5/22) that don't seem to be showing up on any of the published
reports (yet). All events appear to be about the same distance (350 km)
from here (Southern California). They aren't far enough away to be
aftershocks of the Guerrero event.
Anyone else get them and / or know where they were?
Approx.
Time (UT) M
09:51 3.8
10:02 3.3
10:26 4.2
10:54 3.2
11:44 3.0
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Acceleration Calculations
Date: Thu, 22 May 1997 13:15:31 -0700
Greetings --
For those of you who do conversions between acceleration, velocity,
displacement, etc. and have Excel, I came across a spreadsheet for
converting between those properties of waves. See
http://www.endevco.com/endcalc.zip
Intended for vibration, this spreadsheet converts between sine-wave
acceleration, velocity, displacement, %g, frequency, p-p, rms, etc., in
various units of measure. Not that these calcs are difficult to do, but
this is fairly conventient and has it all in one place. I had to change
the cell format to scientific notation, however, to accomodate the small
values used in seismic work.
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Doug Crice <dcrice@............>
Subject: GPR time systems
Date: Thu, 22 May 1997 14:08:30 -0700
Robert Goering (904-763-5930) has a couple of True-Time GPS satelite
time code receivers for sale. He deals in surplus electronics gear and
recently purchased these from the Air Froce.
Besides navigation information, the GPS system broadcasts highly
accurate time codes which can be used as a precise clock. Serious
seismologists use such devices to precisly time earthquake arrivals.
Robert can give you more details, and True-Time in Santa Rosa, CA could
probably tell you more.
Doug Crice
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: JACK HERRON <JHERRON@.........>
Subject: Re: GPR time systems
Date: Thu, 22 May 1997 16:39:52 -0700
At 02:08 PM 5/22/97 -0700, you wrote:
>Robert Goering (904-763-5930) has a couple of True-Time GPS satelite
>time code receivers for sale. He deals in surplus electronics gear and
>recently purchased these from the Air Froce.
>
>Besides navigation information, the GPS system broadcasts highly
>accurate time codes which can be used as a precise clock. Serious
>seismologists use such devices to precisly time earthquake arrivals.
>Robert can give you more details, and True-Time in Santa Rosa, CA could
>probably tell you more.
>
>Doug Crice
>
Doug,
Save us some long distance charges and tell us what he wants for the
units. Price is important to some of us!
Jack
-----------------------------------------
Jack Herron - Editor
Society for Amateur Scientists
8118 E. 20th St.
Tucson, AZ 85710 USA
jherron@.........
520 885-6933
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Bill Scolnik <wls@.........>
Subject: Re: GPR time systems
Date: Thu, 22 May 1997 22:05:47 -0400 (EDT)
What At 02:08 PM 5/22/97 -0700, Doug Crice wrote:
>Robert Goering (904-763-5930) has a couple of True-Time GPS satelite
>time code receivers for sale. He deals in surplus electronics gear and
>recently purchased these from the Air Froce.
>
>Besides navigation information, the GPS system broadcasts highly
>accurate time codes which can be used as a precise clock. Serious
>seismologists use such devices to precisly time earthquake arrivals.
>Robert can give you more details, and True-Time in Santa Rosa, CA could
>probably tell you more.
>
>Doug Crice
>
What Robert has for sale are GOES receivers, not GPS. They are capable of
receiving timing signals from one of two GOES satellites (GOES East and
GOES West). The timing signals received are not as precise as what the GPS
satellites provide, but are accurate to a few hundred ms.
Bill Scolnik
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Public Seismic Network Mailing List (PSN-L)
From: Doug Crice <dcrice@............>
Subject: Re: GPR time systems
Date: Thu, 22 May 1997 18:17:41 -0700
Robert and I didn't discuss prices for the GPS time code receivers. I
was actually talking to Robert to buy the ABEM seismographs seen in an
earlier post. He asked me what these things were and I told him and
also said I would spread the word a little. I am quite happy with the
price I paid for the exploration seismographs.
Doug Crice
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Stephen Caruso <scaruso@......................>
Subject: Re: GPR time systems
Date: Thu, 22 May 1997 22:35:43 -0400 (EDT)
HI I'm new hear! as anybody had any experience w/DataQ acqusition
modules/software? I "acquired" :-0 one recently and planned to use it in
conjunction with a dedicated compaq 386. Would it be possible to use this
other software that is available (i.e. alarm, event only recording etc.).
I built a lehman and have his specified chart recorder available if there
is any one interested.
In Italy, a caruso is a little boy that works in the sulphur mine.
(*)(*)(*)(*)(*)(*)(*)(*))*()(*)*()*()(*)(*)*)(*)(*)(*)(*)(*)(*)*()(*)(*)(*)*)
STEPHEN CARUSO
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Public Seismic Network Mailing List (PSN-L)
From: "Stephen Emert" <semert@........>
Subject: EMON V6.1h
Date: Fri, 23 May 1997 01:21:37 -0400
Does anyone know where I can find this version of EMON avail. for download?
It is said to support several more A/D cards than the version at PSN. I
have a newly constructed sensor just begging to be hooked up!
Stephen Emert
semert@........
http://www.public.usit.net/semert/
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Public Seismic Network Mailing List (PSN-L)
From: R7Giovanni@.......
Subject: Re: GPR time systems
Date: Fri, 23 May 1997 07:41:59 -0400 (EDT)
I have set the antenna outside, and both of them are working. They are model
number 468-dc, and serial numbers 222 and 2184. Thanks...
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Doug Crice <dcrice@............>
Subject: Re: GPS time systems
Date: Fri, 23 May 1997 06:41:05 -0700
Bill Scolink corrected my message about the satelite time code radios.
Thanks Bill, I would feel really bad if I misled somebody about these
things. But, if they are only good to a few hundred milliseconds, what
good are they? There are plenty of clocks that acurate with a lot less
hassle.
Doug Crice
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: bob@................. (Bob Hammond (USGS-AVO Geophysicist))
Subject: Re: EMON V6.1h
Date: Fri, 23 May 1997 08:57:28 -0800
I take your message to mean that you were unable to read the emon6.1h file I sent to you?
Bob
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: GPS time systems
Date: Fri, 23 May 1997 18:43:23 -0800
"But, if they are only good to a few hundred milliseconds, what
good are they? There are plenty of clocks that acurate with a lot less
hassle.
Doug Crice"
******************************
The accuracy of these clocks is + - 1 ms, according to the manual.
JCLahr
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Bill Scolnik <wls@.........>
Subject: Re: GPS time systems
Date: Sat, 24 May 1997 00:40:13 -0400 (EDT)
At 06:41 AM 5/23/97 -0700, Doug Crice wrote:
>Bill Scolink corrected my message about the satelite time code radios.
>
>Thanks Bill, I would feel really bad if I misled somebody about these
>things. But, if they are only good to a few hundred milliseconds, what
>good are they? There are plenty of clocks that acurate with a lot less
>hassle.
>
>Doug Crice
>
>_____________________________________________________________________
>Doug,
Although the GOES receivers aren't nearly as accurate as the GPS receivers,
I really was a little glib when I said 200ms. A properly set up GOES
receiver, with the GOES satellites operating correctly is probably capable
of less than 50ms error.(I've occasionally had precision better than 50ms
with my GOES receiver but it is frequently out more than 100ms). The
problem is that the GOES time signals are sent to the satellite from a
station on earth and then retransmitted from the satellite back to earth.
Corrections for the mean path delay have to be applied both at the
transmitting end and the receiving end. In addition, the satellites orbit
is neither perfectly circular nor precisely in the plane of the equator.
The path delay to the receiving station varies because of this and must be
corrected at the receiver. I've been told that a properly corrected signal
is capable of +-100 microseconds but I've never seen anything near this
with my receivers nor has anyone else that I've spoken to that have used
the GOES time code. They're decent receivers though and a heck of a lot
better than WWV. Today though, even a cheap GPS receiver will give you a
1pps output to within a mucrosecond. Sorry if I misled anyone.
Bill Scolnik
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie & Terri Thompson <ct@.......>
Subject: Re: GPS time systems
Date: Sat, 24 May 1997 10:54:56 -0500
What receiver frequency is the GOES time code receiver using?
Is it 1691 or some 400 MHz range? I see stream monitors
near my house with little crossed yagi antenna arrays pointing
at the Clark belt. My estimate is that they are on something
other than 1691MHz. Anybody know?
thanks,
Charlie
At 12:40 AM 5/24/97 -0400, you wrote:
>At 06:41 AM 5/23/97 -0700, Doug Crice wrote:
>>Bill Scolink corrected my message about the satelite time code radios.
>>
>>Thanks Bill, I would feel really bad if I misled somebody about these
>>things. But, if they are only good to a few hundred milliseconds, what
>>good are they? There are plenty of clocks that acurate with a lot less
>>hassle.
>>
>>Doug Crice
>>
>>_____________________________________________________________________
>>Doug,
>Although the GOES receivers aren't nearly as accurate as the GPS receivers,
>I really was a little glib when I said 200ms. A properly set up GOES
>receiver, with the GOES satellites operating correctly is probably capable
>of less than 50ms error.(I've occasionally had precision better than 50ms
>with my GOES receiver but it is frequently out more than 100ms). The
>problem is that the GOES time signals are sent to the satellite from a
>station on earth and then retransmitted from the satellite back to earth.
>Corrections for the mean path delay have to be applied both at the
>transmitting end and the receiving end. In addition, the satellites orbit
>is neither perfectly circular nor precisely in the plane of the equator.
>The path delay to the receiving station varies because of this and must be
>corrected at the receiver. I've been told that a properly corrected signal
>is capable of +-100 microseconds but I've never seen anything near this
>with my receivers nor has anyone else that I've spoken to that have used
>the GOES time code. They're decent receivers though and a heck of a lot
>better than WWV. Today though, even a cheap GPS receiver will give you a
>1pps output to within a mucrosecond. Sorry if I misled anyone.
>Bill Scolnik
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
_ ________________________________________________ _
/ ) | | ( \
/ / | Charlie Thompson WB4HVD | \ \
_( (_ | _ e-mail: ct@....... _ | _) )_
(((\ \> |/ ) http://www.onr.com/user/ct/ct.html ( \| </ /)))
(\\\\ \_/ / Latitude 30.112 N \ \_/ ////)
\ / Longitude 97.891 W \ /
\ _/ Seismic Station .BUE \_ /
/ / |________________________________________________| \ \
/ / \ \
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ralvarez@........ (Raul Alvarez)
Subject: Re: GPS time systems
Date: Sat, 24 May 1997 21:32:33 -0600 (MDT)
>What receiver frequency is the GOES time code receiver using?
>Is it 1691 or some 400 MHz range? I see stream monitors
>near my house with little crossed yagi antenna arrays pointing
>at the Clark belt. My estimate is that they are on something
>other than 1691MHz. Anybody know?
>
>thanks,
>Charlie
>
>
Charlie,
The time codes are on 468.825 and 468.875 mhz
the river monitors uplink to GOES on 400 - 406 mhz approx.
The time codes are uplinked from Boulder CO.
Raul
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~ ~
~"My dreams are the seeds of my reality, ~
~ nurtured in the womb of my soul" ~
~ RJA, 1985 ~
~ ~
~ ~
~ Raul J. Alvarez ~
~ e-mail ralvarez@........ ~
~ homepage www.frii.com/~ralvarez ~
~ "The Renaissance Experimenter" ~
~ experimenter in: ~
~ Radio and Optical Astronomy, Seismology, Weather, ~
~ Computers, Instrumentation and Neat Stuff! ~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ralvarez@........ (Raul Alvarez)
Subject: Microbarographs
Date: Sat, 24 May 1997 21:43:28 -0600 (MDT)
Interesting reading for you microbarograph builders.
"Transactions of the american geophysical union" nineteenth annual meeting
April 27 to 30, 1938
Page 125-128
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~ ~
~"My dreams are the seeds of my reality, ~
~ nurtured in the womb of my soul" ~
~ RJA, 1985 ~
~ ~
~ ~
~ Raul J. Alvarez ~
~ e-mail ralvarez@........ ~
~ homepage www.frii.com/~ralvarez ~
~ "The Renaissance Experimenter" ~
~ experimenter in: ~
~ Radio and Optical Astronomy, Seismology, Weather, ~
~ Computers, Instrumentation and Neat Stuff! ~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: GPS time systems
Date: Sun, 25 May 1997 01:18:20 -0700
At 12:40 AM 5/24/97 -0400, you wrote:
Bill Scolnik,
>Although the GOES receivers aren't nearly as accurate as the GPS receivers,
>I really was a little glib when I said 200ms. A properly set up GOES
>receiver, with the GOES satellites operating correctly is probably capable
>of less than 50ms error.(I've occasionally had precision better than 50ms
>with my GOES receiver but it is frequently out more than 100ms). The
>problem is that the GOES time signals are sent to the satellite from a
>station on earth and then retransmitted from the satellite back to earth.
>Corrections for the mean path delay have to be applied both at the
>transmitting end and the receiving end. In addition, the satellites orbit
>is neither perfectly circular nor precisely in the plane of the equator.
>The path delay to the receiving station varies because of this and must be
>corrected at the receiver. I've been told that a properly corrected signal
>is capable of +-100 microseconds but I've never seen anything near this
>with my receivers nor has anyone else that I've spoken to that have used
>the GOES time code. They're decent receivers though and a heck of a lot
>better than WWV.
Well I'm not sure about that. If The GOES time system is no better then
50MS then WWV can be better, if you live somewhere here in the states
(excluding Hawaii and Alaska). My SDR software, and the tone decoder on my
A/D card, can keep it's internal time within a few MS if you can get fair
reception to one
of the WWV frequencies. Obviously the farther away from the WWV stations
you are the more propagational errors will occur.
-Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Paranoia Runs Deep...
Date: Sun, 25 May 1997 02:07:35 -0700
Hi,
I thought everyone would get kick out of this. I mailed one of my
Amp/Filter cards (with a wired power supply) and A/D board to a College in
Arizona about two weeks ago. I got this from the person who ordered the
boards the other day:
>Hi Larry,
> I have to tell you this story:
> I received your package today. I was getting worried it was lost in
>the system, but I talked to our chief of public safety today and he told
>me an interesting story. Since the package bore no specific name somebody
>else looked inside and freaked out at all the wrapping and electronics.
>They told the police about it and said it must be a bomb. Since our city
>bomb squad was busy, the state police bomb squad had to come down from
>Phoenix. They had a dog check it out and evacuated the entire building.
>They then sent a robot in, X-rayed it, and decided it was safe. I asked
>him if this package had a return address in Redwood City and he said yes!
>I got quite a laugh out of it, and was glad to get it...
Apparently someone was sending a lot of strange theories to the various
departments of the school and got angry when they told him it was hogwash.
Since then the guy has threatened to bomb various parts of the campus. I'm
just glad they didn't blowup the box like you see on the news now and then!
I'm not sure if the postal insurance covers this<G>.
Have a good one...
-Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: new listing
Date: Sun, 25 May 1997 22:26:16 +1200
Hi all,
there is a new station on the map and list...... Please
welcome Clark Wockner from
Watseka, Illinois, USA to the group.
Clark we look forward to seeing event files from you in the future.
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: MAJ Kermadec quake
Date: Mon, 26 May 1997 11:57:58 +1200
hi all,
well my seismograph needle was really rocking and SDR hit the stops
Prelim. Mag from The NZ Seismo Obs. is M7.5 in the southern Kermadecs
felt all over Nth Is of NZ and areas in the top half of the Sth Is.
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: MAJ Kermadec quake
Date: Sun, 25 May 1997 16:26:38 -0700
At 11:57 AM 5/26/97 +1200, you wrote:
>hi all,
>
> well my seismograph needle was really rocking and SDR hit the stops
>
>
> Prelim. Mag from The NZ Seismo Obs. is M7.5 in the southern Kermadecs
>
> felt all over Nth Is of NZ and areas in the top half of the Sth Is.
>
Seems to be a deep event. I'm not getting large surface waves from this
one. I get a distance of about 9500km from me if I use a 470km (just a WAG)
depth JB table.
-Larry Cochrane
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: MAJ Kermadec quake
Date: Mon, 26 May 1997 12:42:07 +1200
OK Larry I'm still waiting for the event to be posted on the USGS latest
event site
Dave
>>
>Seems to be a deep event. I'm not getting large surface waves from this
>one. I get a distance of about 9500km from me if I use a 470km (just a WAG)
>depth JB table.
>
>-Larry Cochrane
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: MAJ Kermadec quake
Date: Sun, 25 May 1997 17:56:37 -0700
Golly, it seems to be awfully big....
M7.5 at Kermedec?
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Kermadec Quake..not yet
Date: Sun, 25 May 1997 18:20:45 -0700
It hasn't shown up on the IDC listing yet either:
http://www.cdidc.org:65120/web-bin/recentevents
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Marnie Gannon <emgannon@.......>
Subject: Re: MAJ Kermadec quake
Date: Sun, 25 May 1997 19:20:04 -0700
Nando News is reporting the EQ a 7.6 with reports of considerable
shaking in New Zealand but no reports of injury or damage. No other
details as yet.
Marnie Gannon
David A Nelson wrote:
>
> OK Larry I'm still waiting for the event to be posted on the USGS latest
> event site
>
> Dave
>
> >>
> >Seems to be a deep event. I'm not getting large surface waves from this
> >one. I get a distance of about 9500km from me if I use a 470km (just a WAG)
> >depth JB table.
> >
> >-Larry Cochrane
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: re kermadec Is.
Date: Mon, 26 May 1997 14:14:38 +1200
Hi all,
STILL no USGS report
but here is the report from the NZ Seis Obs. in Wellington city
U.T.: 1997 May 25 2322
NZST: 1997 May 26 11.22 a.m.
Lat, Long: 32.72S 178.41W
Location: Southern Kermadec Islands
Focal depth: 518 km
Magnitude: 7.6 Felt widely in the North Island and as far south
as Christchurch.
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Marnie Gannon <emgannon@.......>
Subject: Re: re kermadec Is.
Date: Sun, 25 May 1997 20:32:08 -0700
David A Nelson wrote:
>
> Hi all,
> STILL no USGS report
>
> but here is the report from the NZ Seis Obs. in Wellington city
>
> U.T.: 1997 May 25 2322
> NZST: 1997 May 26 11.22 a.m.
> Lat, Long: 32.72S 178.41W
> Location: Southern Kermadec Islands
> Focal depth: 518 km
> Magnitude: 7.6 Felt widely in the North Island and as far south
> as Christchurch.
>
> Dave
> Dave A. Nelson
Here's an AP news report:
http://wp1.washingtonpost.com/wp-srv/WAPO/19970525/V000436-052597-idx.html
BUT...http://quake.wr.usgs.gov/cgi-bin/quake/gldfs.cr.usgs.gov is
reporting the quake as:
97/05/25 23:22:34 31.99S 179.19E 345.5 6.1Mb B KERMADEC ISLANDS REGION
Marnie Gannon
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: re kermadec Is., USGS numbers
Date: Sun, 25 May 1997 18:39:06 -0700
At 02:14 PM 5/26/97 +1200, Dave wrote:
>Hi all,
> STILL no USGS report
>
> but here is the report from the NZ Seis Obs. in Wellington city
>
>U.T.: 1997 May 25 2322
> NZST: 1997 May 26 11.22 a.m.
> Lat, Long: 32.72S 178.41W
> Location: Southern Kermadec Islands
> Focal depth: 518 km
> Magnitude: 7.6 Felt widely in the North Island and as far south
>as Christchurch.
Here are the NEIS (finger quake@.................. numbers for the event:
97/05/25 23:22:34 31.99S 179.19E 345.5 6.1Mb B KERMADEC ISLANDS REGION
-Larry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: re kermadec Is., USGS numbers
Date: Mon, 26 May 1997 16:24:45 +1200
I find it haed to believe that it is listed at only Mb 6.1 this event
has 10X the amplitude of the Mb6.6 of the 03 May 97 on the drum record
++ that Mb 6.6 wasn't felt over 2/3's of New Zealand as this latest one was
Caltech gave it a Mw of 7.0 I think NEIC/USGS mite be a bit low
the way it goes I suppose esp. when their recorders are a long way
from the epic
Dave
>
>Here are the NEIS (finger quake@.................. numbers for the event:
>
>97/05/25 23:22:34 31.99S 179.19E 345.5 6.1Mb B KERMADEC ISLANDS REGION
>
>-Larry
>
>
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: re kermadec Is., USGS numbers
Date: Sun, 25 May 1997 21:50:04 -0700
Dave,
Where are you getting the Caltech MT reading?
I agree the Mercalli does not fit the NEIC analysis. But remember it is
a National Holiday, it is Saturday night in Golden, and the NEIC has had
there personnel budget slashed. Who ever is on duty is probably not too
pleased to have to come down and process the event.
I'm sure the situation will be rectified on Tuesday.
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: re kermadec Is.
Date: Sun, 25 May 1997 21:53:47 -0700
BTW: the NEIC auto locater map at:
http://wwwneic.cr.usgs.gov/neis/bulletin/970525232234.HTML
Shows a red dot, which translates to a M7+
Orange for M6+ and Yellow for M5s or less.
The Mb 6.1 may be a typo and should be Mb 7.1. What do ya think?
--
---/----
Charlie
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: re kermadec Is.
Date: Mon, 26 May 1997 17:55:54 +1200
Oh ok Charles,
I noticed the red dot, but didn't know if that related to magnitude or
depth
I am on an auto mailer list for the Caltech Mw reports
Return-Path: <autocmtlist-relay@...............>
From: Jascha Polet <polet@...............>
Date: Sun, 25 May 1997 20:03:41 -0700 (PDT)
To: autocmtlist@...............
Subject: CMT Mw=7.0 KERMADEC ISLANDS REGION .............
see if you can make headway with the above info you subscribe to it as
with other listings
I cannot remember the exact wording at it has been almost a year now
You get a full page of data for the event almost identical to the one
on the USGS page under the Moment tensor sub-page..... shows the
beachball etc there is often a 0.2 - 0.5 Magnitude difference between
them and the USGS
the advantage is that the Caltech posting comes out LONG before the USGS one
Dave
At 09:53 PM 5/25/97 -0700, you wrote:
>BTW: the NEIC auto locater map at:
>
>http://wwwneic.cr.usgs.gov/neis/bulletin/970525232234.HTML
>
>Shows a red dot, which translates to a M7+
>
>Orange for M6+ and Yellow for M5s or less.
>
>The Mb 6.1 may be a typo and should be Mb 7.1. What do ya think?
>
>--
>---/----
>Charlie
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Roger Sorensen <Roger.Sorensen@................>
Subject: Lehman period calculation
Date: Mon, 26 May 1997 16:38:28 -0700
Hello all!
I'm trying to calculate the period of a Lehman type
sensor. I poked around the PSN sites but didn't see
the formula.
Would someone be kind enough to take a look at my
calculations?
Here we go...
Divide the Pendulum length (the boom) by the Gravity constant.
Find the square root of the result.
Multiply that by 2 * 3.14159
Then, because of the horizontal boom configuration...
Divide the result, so far, by the Sin of the angle
formed by the boom and support wire.
Example (20" boom w/ 30 degree support wire):
20/32 = 0.625
square root of 0.625 = .79057
..79057 * 2 * 3.14159 = 4.9673
4.9673 / sin(30 degrees) = 10 second period (rounding along the way)
Am I way off base here? Are there other factors I'm forgetting?
If so, please explain what I'm doing wrong.
Thanks!
Roger
Chatsworth, CA
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Lehman period calculation
Date: Mon, 26 May 1997 17:27:13 -0700
Roger Sorensen wrote:
>
> Hello all!
>
> I'm trying to calculate the period of a Lehman type
> sensor. I poked around the PSN sites but didn't see
> the formula.
>
> Would someone be kind enough to take a look at my
> calculations?
>
> Here we go...
>
> Divide the Pendulum length (the boom) by the Gravity constant.
> Find the square root of the result.
> Multiply that by 2 * 3.14159
>
> Then, because of the horizontal boom configuration...
>
> Divide the result, so far, by the Sin of the angle
> formed by the boom and support wire.
>
> Example (20" boom w/ 30 degree support wire):
>
> 20/32 = 0.625
> square root of 0.625 = .79057
> .79057 * 2 * 3.14159 = 4.9673
> 4.9673 / sin(30 degrees) = 10 second period (rounding along the way)
>
> Am I way off base here? Are there other factors I'm forgetting?
> If so, please explain what I'm doing wrong.
>
Hi
The period of the pendulum is a function of the length, as you
indicated , and the inclination of a line between the two piviots from
vertical*.
According to Prof. Bolt "An introduction to the theory of Seismology" p.
204 , the angular freq = sqrt(gi/l) where g=gravity,l=modified pendulum
length (adjusted for the mass distribution), and i is the hinge angle
,which would be :
tan(inclination /dist.between hinges) for small angles.
so let see (for a lumped mass at the end):
if the inclination is 0.05" in a 10" hinge space then i=0.005 radians
then freq=sqrt(0.005*32*12/(20"*2))=0.21 rad/sec (watching units)
then the period=1/freq= 4.6 sec
seems a little fast but I haven't verified it though
I hope this helps a little or generates more comments.
Barry
* decreasing this angle increases the period but the sensor requires
more attention because the pendulum is more sensitive to tilting eg.
drift.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: re kermadec Is., USGS numbers
Date: Mon, 26 May 1997 19:58:26 -0600
Charlie-
That is a pretty complicated seismic source and directivity model you
have proposed below.
-Edward
Charles Watson wrote:
>
> Dave,
>
> Where are you getting the Caltech MT reading?
>
> I agree the Mercalli does not fit the NEIC analysis. But remember it is
> a National Holiday, it is Saturday night in Golden, and the NEIC has had
> there personnel budget slashed. Who ever is on duty is probably not too
> pleased to have to come down and process the event.
>
> I'm sure the situation will be rectified on Tuesday.
>
> --
> ---/----
> Charles P. Watson, Consulting Geologist
> Advanced Geologic Exploration
> Seismo-Watch / Earthquake Information Services
> Voice: 702-852-0992 / Fax: 702-852-3226
> mailto:watson@................
> http://www.seismo-watch.com
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: re kermadec Is., USGS numbers
Date: Mon, 26 May 1997 21:44:52 -0700
Edward Cranswick wrote:
>
> Charlie-
> That is a pretty complicated seismic source and directivity model you
> have proposed below.
> -Edward
>
Would that be Forward or Backward Directivity? ;)
--
---/----
Charlie
> Charles Watson wrote:
> >
> > Dave,
> >
> > Where are you getting the Caltech MT reading?
> >
> > I agree the Mercalli does not fit the NEIC analysis. But remember it is
> > a National Holiday, it is Saturday night in Golden, and the NEIC has had
> > there personnel budget slashed. Who ever is on duty is probably not too
> > pleased to have to come down and process the event.
> >
> > I'm sure the situation will be rectified on Tuesday.
> >
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Jannis, I.H. Lare, van" <JvanLare@..............>
Subject: looking for a seismograph
Date: Tue, 27 May 1997 15:04:51 -0400
Hi all,
Several years ago I tried to build my own seismograph, but it =
wasn't such a success, since I'm not that great in electronics.
Here is my question:
Does anyone on this list know where I might buy a seismograph =
which is able to detect local AND large distant quakes?
Thanks in advance.
Jannis van Lare
Nieuwvliet, The Netherlands
e-mail: JvanLare@..............
=
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Re: Lehman Period Calculation
Date: Tue, 27 May 1997 17:29:09 -0700
Hi Roger --
I went through this about 6 months ago, and here's what I have. Please let
me know if you need further explanation on something, or if I've missed
something.
The equation for the period of a simple pendulum is
t = (2*pi)/sqrt(g/L) (1)
Where t is the period, g is the acceleration due to gravity, and L is the
length of the pendulum. Many introductory physics text books have this
equation, along with its derivation.
In the simple pendulum, the oscillation is due an exchange between
potential and kinetic energy, the same as in the Lehman. Although I
haven't gone through the math, I believe the geometry of the Lehman is
close enough to that of the simple pendulum to be able to use the above
equation for the Lehman, if the excursions of the mass are small.
In both the Lehman and the simple pendulum, any movement of the mass from
its rest position results in its being lifted against gravity. The process
here is to determine the amount of that lift for a small horizontal
displacement for the Lehman (1mm, for instance), then compute the length of
the equivalent simple pendulum, then apply the above formula to find the
period.
Lets assign some variables:
a = boom length from pivot to mass.
b = vertical distance between top and bottom pivot.
d = horizontal offset distance between top and bottom pivot.
Looking at the Lehman from the top, imagine for a moment that the boom can
swing all the way to 90 degrees from its rest position. At the 90-degree
point, the mass will be lifted by
h = d * a / b (2)
At any other boom angle th (still looking from the top), the amount of lift
will be
y = h * (1 - cos(th)) (3)
Suppose the mass is moved from its rest position some small distance x.
The boom angle will be
th = arctan(x/a) which is approximately the same as
th = arcsin(x/a) if the angle is small, which is the case here.
So the mass is lifted by
y = h * (1 - cos(arcsin(x/a)) (4)
but since arcsin(x/a) = arccos(sqrt(1-(x/a)^2)),
y = h * (1 - sqrt(1 - (x/a)^2)) , or
y = d * a / b * (1 - sqrt(1 - (x/a)^2)) (5)
Now, for the simple pendulum, the amount the mass is lifted when it is
moved from its rest position some small distance x is
y = L - sqrt(L^2 - x^2) (6)
where L is the length of the pendulum.
Equations 5 and 6 can be combined and manipulated to solve for L, the
length of the equivalent simple pendulum, but I think it is easier to
construct a hypothetical case and use actual numbers.
Suppose a = 400mm, b = 250mm, d = 1mm, and x = 1mm. I think this is
probably a representative situation. Solving (5), y = 5e-9m . This is the
amount of lift on the Lehman by moving the mass 1mm from its rest position.
Using (6), and 5e-9m for y, 1mm for x, and solving (6) for L, gives about
99 meters. Solving (1) gives a period of about 20 seconds.
Karl Cunningham
La Mesa, CA.
karlc@.........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Stephen Caruso <scaruso@......................>
Subject: DataQ acquisition modules?
Date: Tue, 27 May 1997 22:24:37 -0400 (EDT)
Enuf already about the pendulum you math freaks! :-{0
Actually I'm glad to see the math.
Apparently no one has had any DataQ experience.
I purchased for $100 the D-190, a 12 bit 240hz potential data acq. module.
Haven't hooked it in yet. Was hoping to hear some feedback.
Also glad to see the expertise in timing and so forth.
Perusing some of the old PSN-L files saw no mention of the 1996 April Sci
Am article utilizing a HET for a sensor. Any takers?
Stephen Caruso CET
KB8UGH
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jim Hannon <jmhannon@........>
Subject: Re: DataQ acquisition modules?
Date: Wed, 28 May 1997 06:08:24 -0500
Stephen Caruso wrote:
>
> Enuf already about the pendulum you math freaks! :-{0
> Actually I'm glad to see the math.
> Apparently no one has had any DataQ experience.
> I purchased for $100 the D-190, a 12 bit 240hz potential data acq. module.
> Haven't hooked it in yet. Was hoping to hear some feedback.
> Also glad to see the expertise in timing and so forth.
> Perusing some of the old PSN-L files saw no mention of the 1996 April Sci
> Am article utilizing a HET for a sensor. Any takers?
>
> Stephen Caruso CET
> KB8UGH
>
>It looks like August 1996 SA had an article Detecting micron sized movements using an HET. I think the April article was on t
he acceleromenter seismograph. Which has been discussed. A potential problem with the HET is that it's response is very likely
to be quite nonlinear. And also subject to the earth's magnetic field variations.
--
Jim Hannon
http://soli.inav.net/~jmhannon/
42,11.90N 91,39.26W
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Rond <rond@................>
Subject: Re: DataQ acquisition modules?
Date: Wed, 28 May 1997 06:50:38 -0500
Stephen,
>Enuf already about the pendulum you math freaks! :-{0
>Actually I'm glad to see the math.
>Apparently no one has had any DataQ experience.
>I purchased for $100 the D-190, a 12 bit 240hz potential data acq. module.
>Haven't hooked it in yet. Was hoping to hear some feedback.
>Also glad to see the expertise in timing and so forth.
>Perusing some of the old PSN-L files saw no mention of the 1996 April Sci
>Am article utilizing a HET for a sensor. Any takers?
Re: the 1996 SciAm article, see the "Please Read" link on Larry Cochrane's
PSN web page (http://psn.quake.net).
Charlie Rond -\/\--Public Seismic Network-Memphis
rond@................ (901) 360-0302 [ free BBS ]
http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Lehman period calc.--Cunningham
Date: 28 May 97 14:37:32 EDT
Karl Cunningham,
Very good, lucid analysis of the period of a Lehman. I checked the whole
thing and found one typo--eq. (1) should be t = 2*pi*sqrt(g/L) rather than
div. by sqrt(g/L).
Aki & Richards, 'Quant. Seismology', vol. 1 p 484 give the formula: period =
2*pi*sqrt(L/(g*sin(th))) where L is the boom length and th is the angle between
the vert. and the line connecting the upper and lower pivots. For your example
dimensions, this gives the same 20" period. (Actually, the formula given sez
cos rather than sin but this gives ridiculous answers.)
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.........>
Subject: Re: Lehman period calc.--Cunningham
Date: Wed, 28 May 1997 12:25:44 -0700
Greetings, Bob --
Respectfully, I believe eq. (1) was correct as written. If L increases,
the period should also increase. It could have been written t =
2*pi*sqrt(L/g).
I like the equation in your citation from Aki & Richards -- far more concise.
-- Karl
At 02:37 PM 5/28/97 EDT, you wrote:
>I checked the whole
>thing and found one typo--eq. (1) should be t = 2*pi*sqrt(g/L) rather than
>div. by sqrt(g/L).
> Aki & Richards, 'Quant. Seismology', vol. 1 p 484 give the formula:
period =
>2*pi*sqrt(L/(g*sin(th))) where L is the boom length and th is the angle
between
>the vert. and the line connecting the upper and lower pivots. For your
example
>dimensions, this gives the same 20" period. (Actually, the formula given sez
>cos rather than sin but this gives ridiculous answers.)
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: quake search engine
Date: Thu, 29 May 1997 10:38:03 +1200
hi all,
I have used the Harvard search engine for finding data on quakes
since 1977 for several years now I just received this e-mail from them
yesterday advising of a new search engine layout....
Dave
270597
To: Harvard CMT web search users <larson@...............>
Subject: NEW on-line CMT search
You may be interested in the new on-line Harvard CMT search engine,
and I am looking for people who will test it for me. The new search
engine allows for searches by date range, Mw, mb, Ms, half duration,
and location.
The URL is: http://www.seismology.harvard.edu/CMTsearch.html
If you find bugs in the new search engine (particularly incorrect
results!), please let me know.
I hope the CMT search engine is helpful in your research.
Erik Larson
____________________________________________________________________
Department of Earth and Planetary Sciences
Harvard University
20 Oxford Street, Cambridge, MA 02138
http://www.seismology.harvard.edu/~larson
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Stephen Caruso <scaruso@......................>
Subject: Re: DataQ acquisition modules?
Date: Wed, 28 May 1997 19:10:11 -0400 (EDT)
Thanks for the response on the HETs.
DataQ must be something unheard of.
STEPHEN CARUSO CET
KB8UGH
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: the revised intensity scale
Date: Thu, 29 May 1997 11:45:22 +1200
Hi all,
we have all (hopefully) heard of the Modified Mercalli intensity scale
for measuring the felt effects of quakes, on a more jovial side I present
the Modified McDonald's Scale I just rediscovered it amongst my paper
mountain
Hopefully not too many of you have seen it before ( I'm not sure whether
it originated in NZ of the good ol' US of A.
I Cokes fizz more
II Cokes slosh
III Drive-in window attendant drops fries, Car rocks
IV Arches sway visibly
V Tiles fall, Kids scream, Merry-go-round doesn't
VI Arches fall, Mothers scream, shakes shake
VII Buildings empty (of people)
VIII Buildings collapse, others don't
IX Others do
X More others do, Everything sloshes
XI Cracks, cracks and more cracks
XII Flying fries, what goes up goes down (faster)
XIII Bad luck
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: DataQ acquisition modules?
Date: Wed, 28 May 1997 17:45:10 -0600
Stephen-
Sometime in 1993-1994, I purchased a sample DataQ 12-bit A/D board with
parallel-port output and some software that produced a realtime chart
display on a VGA monitor under DOS, but I do not have any further
details about it. I was thinking of using it for a PSN/USGS school
project that Steve Hammond (San Jose PSN) and I were planning. Tom
Bice, USGS Golden, made a power supply for the A/D board and an
amplifier to connect it to a cheap 4.5 Hz geophone ($50). I
demonstrated the system to Steve in July/August 1994, and it worked
quite nicely as a demo. For various reasons, including the Northridge
Earthquake and the employment situation in the Bay Area then, the school
project never got further under way. As far as I know, Steve still has
the system, not including the geophone; he might be able to help you
<shammond@..........>.
-Edward
Stephen Caruso wrote:
>
> Thanks for the response on the HETs.
> DataQ must be something unheard of.
> STEPHEN CARUSO CET
> KB8UGH
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Should the PSN be affiliated with the CNSS?
Date: Wed, 28 May 1997 19:29:47 -0600
PSN Members-
I recently received a request for some information:
>Subject:
> Telemetry stations
> Date:
> Wed, 28 May 1997 06:26:04 -0700
> From:
> Bob Lewis <r-lewis5@......>
> To:
> "Edward Cranswick, Lakewood, CO "<cranswick@..................>
>
>
>Ed, do you know if there are any telemetered seismic stations in the Dallas,
>TX. area? I know this is not an active area like California but I thought there
>might be some.
>
>Thanks...
>
>
>Bob Lewis WB5FDF
As pointed out to me by Steve Malone, Chairperson of the Council of the
National Seismic System (CNSS), alot of this information is available
from the CNSS website:
> Ed, I suggest that you refer them to the CNSS WEB pages which includes,
> besides lots of other things, maps and detailed descriptions of all
> networks operated by CNSS members. They can be found at:
> http://www.cnss.org
>
> There may or may not be the specific information this person wants in
> these pages, but there are many contact people listed in the area of
> his interest to whom he could direct his question.
(In the Nov/Dec 1996 issue of "Seismological Research Letters", Steve
Malone referred to the Redwood City PSN website in his "Electronic
Seismologist" column entitled "'Near' Real-time Seismology")
I suggest that you all look at the CNSS website <http://www.cnss.org>
because it raises another question. I attended the CNSS Meeting in
Memphis in Feb 1997 as an "unofficial" representative of the PSN. At
that time, I did make an informal presentation of the PSN using the PSN
websites displayed on a monitor, and I did make a formal request that
the PSN be included in future CNSS concerns. However, that has not been
spelled out in the meeting minutes and resolutions displayed at the CNSS
website -- though some of these are in draft form as yet and can be
modified.
Please let us know whether you think that we, the PSN, should apply to
be recognized as a network affiliated with the CNSS.
-Edward
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Should the PSN be affiliated with the CNSS?
Date: Wed, 28 May 1997 20:08:09 -0700
Edward Cranswick wrote:
>
> PSN Members-
>
> I suggest that you all look at the CNSS website <http://www.cnss.org>
> because it raises another question. I attended the CNSS Meeting in
> Memphis in Feb 1997 as an "unofficial" representative of the PSN. At
> that time, I did make an informal presentation of the PSN using the PSN
> websites displayed on a monitor, and I did make a formal request that
> the PSN be included in future CNSS concerns. However, that has not been
> spelled out in the meeting minutes and resolutions displayed at the CNSS
> website -- though some of these are in draft form as yet and can be
> modified.
>
> Please let us know whether you think that we, the PSN, should apply to
> be recognized as a network affiliated with the CNSS.
>
> -Edward
>
My concern involves "accurate" representation of info, specifically time
and amplitude. I seems that we all should have consistent times. Also I
think we are measuring both velocity and accelerations ,depending on
station. How can we get calibrated times and amplitudes for all our
sites when we are spread out so much? Personally, I think our waveforms
look much better in many instances that the "professionals".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: JIM CRISTIANO <weitech@..........>
Subject: Re: DataQ acquisition modules?
Date: Thu, 29 May 1997 07:59:29 -0700
Stephen Caruso wrote:
>
> Thanks for the response on the HETs.
> DataQ must be something unheard of.
> STEPHEN CARUSO CET
> KB8UGH
If you are looking for info on DATAQ instruments, they are at
www.dataq.com.
Are you guys mixing up HALL EFFECT TRANSISTORS (HET) with the Analog
Devices
ADXL50 accelerometer? Maybe I missed something.
Jim Cristiano cristiano@...........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: [Fwd: Re: CNSS meeting]
Date: Thu, 29 May 1997 10:17:00 -0600
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
Bob-
If you have no objection I will forward this to PSN-L because I would
like to see this discussion available to all: I don't have the
authority or mental wherewithal to perform any kind of coordination
other than the informal connection I provide between the USGS and the
PSN.
-Edward
Bob Lewis wrote:
>
> I looked at the CNSS Web site and read their charter. Only "institutions and
> agencies of the U.S. government" seem to be eligible for membership. I would
> take this to mean that they DON'T WANT people like "us", "amateurs". I have
> run across this occasionally in my 33 years as an "amateur" radio operator
> also. Some people take "amateur" to mean: "not really knowing what you're
> doing". This is definitely NOT the case most of the time. While it's true
> that most of us can't afford an STS-2 with a 24-bit data logging system and an
> elaborate vault, we do pretty well with what we've got. As far as timing goes,
> in my case at least, my computer's clock is synched to my GPS clock/frequency
> standard, so my time error is essentially zero. I also what my magnification
> is, trace amplitude vs. ground motion. It's true that not all of us have
> three-component systems and nice quiet sites. I guess they think that we, as
> amateurs, could never possibly contribute anything worthwhile. I wonder if
> the CNSS even looked at what we're doing and what are capabilities and levels
> of expertise are? It looks like the answer to that would be NO.
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
From: roger baker <rcbaker@........>
Subject: Earth Field
Date: Thu, 29 May 1997 15:27:37 -0500 (CDT)
Friends,
I have done a little further work on a cheap and easy
(jellybean) seismometer design and am almost irresistably attracted
to the idea of various magnetic suspension options. So one major design
question is how much the earth's field varies on a day to day basis.
Is it one part in a million on a slow diurnal basis or what? Since the
fields used in an instrument are likely to be hundreds of times the
earth's field, even a variation of a hundred parts per million might not
be serious, especially if slow. A bigger design concern is undoubtedly the
change in magnetic field strengh of ceramic magnets with temperature,
which however can be compensated by temperature controls.
--Yours, Roger
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David Josephson <david@...............>
Subject: Re: Earth Field
Date: Thu, 29 May 1997 13:43:25 -0700 (PDT)
On Thu, 29 May 1997, roger baker wrote:
> Friends,
> I have done a little further work on a cheap and easy
> (jellybean) seismometer design and am almost irresistably attracted
> to the idea of various magnetic suspension options. So one major design
> question is how much the earth's field varies on a day to day basis.
> Is it one part in a million on a slow diurnal basis or what? Since the
In mid latitudes like most of the US, the field varies on a diurnal
basis by 1 to a few tens of nT from a mean of around 50 uT (so, 1 in 5000
to 1 in 50,000 more or less). During ionospheric disturbances there
can be variations of as much as a few hundred nT. There are also
variations with periods from a few seconds to a few milliseconds
called micropulsations, of ionospheric origin, and the magnetic
signature from changing telluric currents which can be a few pT to a
few nT in the band 0.01 to about 50 Hz. Any place where there is
large DC power distribution (electric trains), variations in current
draw can make magnetic field changes of a few tens of nT, much more
when you are close to the source. The magnetic noise at Sunnyvale for
instance changes by 1 to 5 nT when Bay Area Rapid Transit is running
(and the closest BART is about 20 miles away).
Magnetically levitated gravimeters (aka accelerometers, aka seismographs)
exist and work quite well (GWR Inc in San Diego) but they have
very effective shields. I think you would need at least a couple
of layers of soft iron or mu-metal shielding enclosing your sensor but
it should be doable.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Stephen Caruso <scaruso@......................>
Subject: analogue vs.?
Date: Thu, 29 May 1997 22:01:37 -0400 (EDT)
Jim I thought maybe there was something funny going on there as well!
I was talking about hall effect transistors originally.
STEPHEN CARUSO CET
KB8UGH
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Stephen Caruso <scaruso@......................>
Subject: Re: DataQ acquisition modules?
Date: Thu, 29 May 1997 22:03:21 -0400 (EDT)
This newer module the D-190 drws it's power from the computer.
I would
have probably waited to buy it had I known there were "amatuer" seismologists
using specific software!
I like the idea of event actualizing. I don't
think, at least, am not aware of this feature in my software. This module
has an
event marker but I need to work w/it some on my own. I bought a dedicated
computer for it yesterday ( used 386 1meg ram). The software has somegood
aspects like stand alone graphics that can be sent and read by others.
I was glad to find this group. and it was good to see the "Lehman" as a
viable thing still in use!
STEPHEN CARUSO CET
KB8UGH
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Michael Chang <pya_cha@..................>
Subject: Talent On Line
Date: Fri, 30 May 1997 16:40:07 -0700
Might be interesting to make the talent pool at PSN available to
educational needs of teachers and students. See below.
>Return-Path: <owner-discovery-school@...................>
>Approved-By: PATK@....................
>Approved-By: daisy <daisyb@..............>
>Date: Thu, 29 May 1997 11:44:03 -0500
>Reply-To: daisyb@..............
>Sender: Educational activities at Discovery Channel Online
> <DISCOVERY-SCHOOL@...................>
>From: daisy <daisyb@..............>
>Organization: InfiNet
>Subject: Talent On Line
>To: Multiple recipients of list DISCOVERY-SCHOOL
> <DISCOVERY-SCHOOL@...................>
>
>HELLO!
>
> I am writing to tell you about a new project which may be of interest
>to you. This project is called Talent On Line and its purpose is to
>make the skills and expertise of talented individuals available to
>teachers and students. Students from three High Schools in Iowa are
>working to populate the Talent On Line database, which teachers and
>students can access using the Internet. Talent On Line is a free
>service. Anyone can visitthe web site, fill out the electronic form
>(which takes about ten minutes), and be listed in the pool of human
>resources.
>
> Teachers and students can search the database by subject or key
word to
>find someone with expertise in the area they are interested in. (For
>example Brenda Lansdowne could search for an expert in plants for her
>unit on plants.) After a search you'll get a list of names of people
>who match your area of interest and ways to contact that person via
>e-mail, postal mail, telephone, etc.
>
> You can help get this project off the ground by becoming part of the
>database. In so doing, other teachers and students can benefit from
>your skills and expertise.
>
>If you would like more information, I can be reached at
>mailto:daisyb@..............
>Please check out our web site! http://www.uni.edu/talent
>Thank you for considering Talent On Line.
>
>Sincerely,
>
>Daisy Barnes
>
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Clark Wockner <clark@.............>
Subject: Lo pass filter ???
Date: Fri, 30 May 1997 15:45:56 -0700
Hi All
Now that I have my Lehman running I have need for a Lo pass
filter. I think I saw a schematic for one at some url in the past but
now I can/t find it again. Does anyone know where it is hiding??
Thanks for your help.
Clark
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: Talent On Line
Date: Fri, 30 May 1997 12:59:27 -0800
Michael,
The talent pool idea sounds good to me. How would it be
to have the PSN list be the point of contact for students
or teachers who want to build seismograph stations? That
way we could all see the questions and answer them as time
and knowledge allows.
It might be a good idea to post the more common questions
and answers in a FAQ area on the web. That way some
questions could be answered quickly by giving the web
URL.
Larry, what do you think?
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Michael Chang <pya_cha@..................>
Subject: Re: Talent On Line
Date: Fri, 30 May 1997 17:21:46 -0700
John,
We can enlist a PSN representitive as a point of contact at the Iowa
University talent pool site, and use the PSN address for any Q&A. Although
I haven't communicated with them, I'm sure Iowa-U would have a means to
accomodate news groups as a talent resource.
At 12:59 PM 5/30/97 -0800, you wrote:
>
>Michael,
>
>The talent pool idea sounds good to me. How would it be
>to have the PSN list be the point of contact for students
>or teachers who want to build seismograph stations? That
>way we could all see the questions and answer them as time
>and knowledge allows.
>
>It might be a good idea to post the more common questions
>and answers in a FAQ area on the web. That way some
>questions could be answered quickly by giving the web
>URL.
>
>Larry, what do you think?
>
>JCLahr
>################################## John C. Lahr
>################################# Seismologist
>################################ U.S. Geological Survey
>############################### c/o Geophysical Institute
>############################## 903 Koyukuk Drive
>~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
>###########################################################
> P.O. Box 757320 ################################
> Fairbanks, AK 99775 #################################
> Phone: (907) 474-7997 ##################################
> Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
> lahr@........ ####################################
> http://www.aeic.alaska.edu/Input/lahr/
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ct@....... (Charlie Thompson)
Subject: Re: Lo pass filter ???
Date: Fri, 30 May 1997 17:52:00 -0500
Clark,
Don't forget to try out the nifty post-processing features
of WinQuake. WinQuake can FFT filter the data any way you like.
This is a useful feature for 'cleaning up' weak teleseismic
events.
-Charlie Thompson
Buda, Texas
>Hi All
> Now that I have my Lehman running I have need for a Lo pass
>filter. I think I saw a schematic for one at some url in the past but
>now I can/t find it again. Does anyone know where it is hiding??
>Thanks for your help.
> Clark
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
-------------------------------------------------------------------------
Charlie Thompson
WB4HVD 30.112N 97.891W
800 Elliott Ranch Rd.
Buda, TX 78610
http://www.onr.com/user/ct/ct.html
Seismic Station .BUE
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: JIM CRISTIANO <weitech@..........>
Subject: Re: Lo pass filter ???
Date: Fri, 30 May 1997 16:00:14 -0700
Clark Wockner wrote:
>
> Hi All
> Now that I have my Lehman running I have need for a Lo pass
> filter. I think I saw a schematic for one at some url in the past but
> now I can/t find it again. Does anyone know where it is hiding??
> Thanks for your help.
> Clark
If Larry doesn't mind (:~O> , you can lift the low pass filter from
his
schematic @ psn.quake.net/eqamp.html.
Jim cristiano@...........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Re: Lehman period calc.--Cunningham
Date: 30 May 97 20:55:36 EDT
Karl,
Oops! When I pass algebra 101, I'll do better.
Bob
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Talent On Line
Date: Fri, 30 May 1997 19:38:03 -0700
At 12:59 PM 5/30/97 -0800, John Lahr wrote:
>
>Michael,
>
>The talent pool idea sounds good to me. How would it be
>to have the PSN list be the point of contact for students
>or teachers who want to build seismograph stations? That
>way we could all see the questions and answer them as time
>and knowledge allows.
>
>It might be a good idea to post the more common questions
>and answers in a FAQ area on the web. That way some
>questions could be answered quickly by giving the web
>URL.
>
>Larry, what do you think?
Fine with me...
-Larry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Rond <rond@................>
Subject: Re: Talent On Line
Date: Sat, 31 May 1997 09:07:12 -0500
With usual enthusiasm, I responded to the first message by registering.
Of course, I intended to refer most questions to you experts. I actually
prefer having a "central" contact person for the PSN. If you agree, let
me know and I will remove my name from their list.
>
>We can enlist a PSN representitive as a point of contact at the Iowa
>University talent pool site, and use the PSN address for any Q&A. Although
>I haven't communicated with them, I'm sure Iowa-U would have a means to
>accomodate news groups as a talent resource.
>
>At 12:59 PM 5/30/97 -0800, you wrote:
>>
>>Michael,
>>
>>The talent pool idea sounds good to me. How would it be
>>to have the PSN list be the point of contact for students
>>or teachers who want to build seismograph stations? That
>>way we could all see the questions and answer them as time
>>and knowledge allows.
>>
>>It might be a good idea to post the more common questions
>>and answers in a FAQ area on the web. That way some
>>questions could be answered quickly by giving the web
>>URL.
>>
>>Larry, what do you think?
>>
>>JCLahr
Charlie Rond -\/\--Public Seismic Network-Memphis
rond@................ (901) 360-0302 [ free BBS ]
http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Norman Davis WB6SHI <normd@.............>
Subject: Re: Lo pass filter ???
Date: Sat, 31 May 1997 07:38:04
At 03:45 PM 5/30/97 -0700, you wrote:
>Hi All
> Now that I have my Lehman running I have need for a Lo pass
>filter. I think I saw a schematic for one at some url in the past but
>now I can/t find it again. Does anyone know where it is hiding??
>Thanks for your help.
> Clark
I would like that info also
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Norman Davis WB6SHI <normd@.............>
Subject: Hall effect sensor.
Date: Sat, 31 May 1997 07:39:29
I would like to hear from someone that is using a hall effect system of
output on there
seismograph. Also schematic would be nice.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Hall effect sensor.
Date: Sat, 31 May 1997 08:38:17 -0700
Norman Davis WB6SHI wrote:
>
> I would like to hear from someone that is using a hall effect system of
> output on there
> seismograph. Also schematic would be nice.
>
Hi Norman
I have also been interested in Hall Effect sensors. I originally
thought they were only used for on/off or switch conditions rather than
variable output apps.I believe concrete trucks use them to count drum
revolutions. I however read a note to this site from Benjamin Boozer on
5/17/97 who talked about Hall Effect sensors. I haven't followed up on
it.
Any input Ben?
Are the sensors linear? subject to more noise than coils? are there
crossover errors? where does one get data sheets or info on the sensors?
Barry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Mark Wilson mark@.............." <wilsonm@............>
Subject: Re: Hall effect sensor.
Date: Sat, 31 May 1997 09:55:19 -0700 (PDT)
On Sat, 31 May 1997, Barry Lotz wrote:
I messed around with a hall effect transducer a few years ago on my
leahman.
Hall effect Switches are just that, switches.
Hall effect Transducers are linear devices. You can get them from
many sources. I got mine from Newarks Electronics.
The one that I was using was a 0 - 5vdc output device that was
linear and temperature compensated.(which was nice) I believe they are
in the neighborhood of 12 - 20 dollars.
Instead of mounting the coil, I used the HET, centered the magnet at 2.5 vdc.
The problem of course is that with the coil you are generating output
from acceleration. With the Hall effect you are getting a linear output.
(True ground movement). What you have to do on the input side is use a
comparator to "null" with an offset voltage. (difference) You are also
working in a positive only environment. (No negative voltage).
I was using a chart recorder for the output with a homebuilt amp/filter.
Since I got my PS1 recorder I went back to a coil/magnet on the garden gate.
Basically the same amplifier will work for both, you just have to build
the front end to null the voltage.
What I really likeed about the HET was that it was clean DC out. It did not
ingress the noise like a coil would. This cuts down on the amount of
filtering you have to do. The bad thing was running the 5VDC to the device.
It is 3 wire, +5VDC, Gnd and output.
I am sure that there are plenty of people on the list that can get you a
schematic of a comparator using a simple circuit. I used a standard opamp
(LM 741 I do believe) If you need a circuit diagram I can post one up.
After you get this built, then the output will feed any filter/amp system.
Hope that helps...
> Norman Davis WB6SHI wrote:
> >
> > I would like to hear from someone that is using a hall effect system of
> > output on there
> > seismograph. Also schematic would be nice.
> >
> Hi Norman
> I have also been interested in Hall Effect sensors. I originally
> thought they were only used for on/off or switch conditions rather than
> variable output apps.I believe concrete trucks use them to count drum
> revolutions. I however read a note to this site from Benjamin Boozer on
> 5/17/97 who talked about Hall Effect sensors. I haven't followed up on
> it.
> Any input Ben?
> Are the sensors linear? subject to more noise than coils? are there
> crossover errors? where does one get data sheets or info on the sensors?
> Barry
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
>
***********************************************************************
--- mark@..............
--- http://www.markwilson.com
--- wilsonm@............
---==== DiscoverNet Network Operations http://www.discover.net ====---
D i s c o v e r Y o u r W o r l d!
***********************************************************************
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Hall effect sensor.
Date: Sat, 31 May 1997 09:36:14 -0700
Mark Wilson mark@.............. wrote:
>
> On Sat, 31 May 1997, Barry Lotz wrote:
> I messed around with a hall effect transducer a few years ago on my
> leahman.
>
> Hall effect Switches are just that, switches.
> Hall effect Transducers are linear devices. You can get them from
> many sources. I got mine from Newarks Electronics.
>
> Hope that helps...
>
> > Norman Davis WB6SHI wrote:
> > >
Thanks Mark
I'll check some sources. It seems the unit would be smaller than
variable air caps and coils if they have reasonable sensitivity. The
only disadvantage to me is measuring acceleration via displacement is
not as "nice" as velocity via a coil.
Barry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: This is a test please ignore
Date: Sat, 31 May 1997 20:34:24 -0700
Sorry about that... Dave Nelson was having problems posting to the list.
-Larry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: hi re test
Date: Sun, 01 Jun 1997 17:04:26 +1200
Gidday,
That message from you came through ok...... Did the system
actually receive the message posted to Charlie and Co in Texas re their
event it got sent twice ?? if not I will try again
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: hi re test
Date: Sat, 31 May 1997 21:07:23 -0700
Hi,
No it never went out. Try sending it again.
-Larry
At 05:04 PM 6/1/97 +1200, you wrote:
>Gidday,
> That message from you came through ok...... Did the system
>actually receive the message posted to Charlie and Co in Texas re their
>event it got sent twice ?? if not I will try again
>
> Dave
> Dave A. Nelson
>
> 24 Jensen St.,
> Green Is., Dunedin,
> South Is.. New Zealand.
>
>http://psn.quake.net/dave/home.htm
>
>
>Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
>Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
> THE DIRECTION OF THE MOST DAMAGE
>Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Lo pass filter ???
Date: Sun, 01 Jun 1997 17:11:26 +1200
Clark,
been having a lot of fun this afternoon cleaning up my
seismograms with the filtering processing in Winquake it works extremely
well...... virtually eliminates the need for electronic filtering assoc.
with the preamp cct
In fact it is benificial to do broadband recording so as not to loose
any info. Then later on apply selective filtering to aquire the wanted info.
Larry C's, Winquake is capable of hi, lo, notch and band pass filtering
very versatile.
Dave
At 03:45 PM 5/30/97 -0700, you wrote:
>Hi All
> Now that I have my Lehman running I have need for a Lo pass
>filter. I think I saw a schematic for one at some url in the past but
>now I can/t find it again. Does anyone know where it is hiding??
>Thanks for your help.
> Clark
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Texan event
Date: Sun, 01 Jun 1997 17:23:28 +1200
Charlie and Co,
Haven't heard from any of you.... Did any of you guys
record the M3.4 Near Dallas a day ago ???
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Lo pass filter ???
Date: Sun, 01 Jun 1997 00:53:34 -0700
At 05:11 PM 6/1/97 +1200, you wrote:
>Clark,
> been having a lot of fun this afternoon cleaning up my
>seismograms with the filtering processing in Winquake it works extremely
>well...... virtually eliminates the need for electronic filtering assoc.
>with the preamp cct
>
> In fact it is benificial to do broadband recording so as not to loose
>any info. Then later on apply selective filtering to aquire the wanted
info.
You still need a low-pass filter before the A/D converter unless you are
over sampling the data with a very high sample rate. Any sampling system
(like a A/D converter system) has a nyqust (sp) frequency point. This is
1/2 the sample rate. Any signal above the nyqust frequency causes errors in
the frequency domain of the input signal. So if you are sampling at 50
samples per second then you need to attenuate any information above 25 hz.
Ideally you want the signal level to be below the dynamic range of the A/D
convert (~70db for a 12 bit system or ~80 db for a 16 bit system) at the
nyqust frequency. If you don't do this (add low-pass filtering) and you
have signals above the nyqust point, then when you do your FFT's and
digital filtering there will be errors in your data.
For low-pass filtering a 6 or 7 pole low-pass filter with a cutoff
frequency starting at 1/2 the nyqust (1/4 the sampling rate) will do. The
amount of filtering also depends on the type of sensor, if you are going to
receive teleseismic events only (low frequency stuff only), and the amount
of local ground noise (usually high frequency stuff). Also there is a
natural high frequency attenuation from the ground movements from
earthquakes, and the local ground noise, so the higher the sampling rate
the less filtering you need to do.
Regards,
Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Texan event
Date: Sun, 01 Jun 1997 11:50:44 +1200
Charlie and Co,
Haven't heard from any of you.... Did any of you guys
record the M3.4 Near Dallas a day ago ???
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: [Fwd: Re: CNSS meeting]
Date: Sun, 01 Jun 1997 01:45:09 -0700
Greetings,
Heres my .02 cents... I'm not sure if they would have us... What Bob brings
up is some of the problems. Since they are only interested in US
institutions and
agencies I'm not sure how we would fit in. Since we are quickly becoming a
international organization with our own event file format I don't think
they would be to interested.
-Larry Cochrane
Redwood City, PSN
>
>Bob-
> If you have no objection I will forward this to PSN-L because I would
>like to see this discussion available to all: I don't have the
>authority or mental wherewithal to perform any kind of coordination
>other than the informal connection I provide between the USGS and the
>PSN.
>-Edward
>
>Bob Lewis wrote:
>>
>> I looked at the CNSS Web site and read their charter. Only
"institutions and
>> agencies of the U.S. government" seem to be eligible for membership. I
would
>> take this to mean that they DON'T WANT people like "us", "amateurs". I
have
>> run across this occasionally in my 33 years as an "amateur" radio operator
>> also. Some people take "amateur" to mean: "not really knowing what you're
>> doing". This is definitely NOT the case most of the time. While it's
true
>> that most of us can't afford an STS-2 with a 24-bit data logging system
and an
>> elaborate vault, we do pretty well with what we've got. As far as
timing goes,
>> in my case at least, my computer's clock is synched to my GPS
clock/frequency
>> standard, so my time error is essentially zero. I also what my
magnification
>> is, trace amplitude vs. ground motion. It's true that not all of us have
>> three-component systems and nice quiet sites. I guess they think that
we, as
>> amateurs, could never possibly contribute anything worthwhile. I
wonder if
>> the CNSS even looked at what we're doing and what are capabilities and
levels
>> of expertise are? It looks like the answer to that would be NO.
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Clark Wockner <clark@.............>
Subject: Re: Texan event
Date: Sun, 01 Jun 1997 07:53:33 -0700
David & Group
The Texas event didn't show up in Illinois.
Clark
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie & Terri Thompson <ct@.......>
Subject: Re: Texan event
Date: Sun, 01 Jun 1997 08:02:50 -0500
I read about the Texas event in this morning's Sunday paper.
I checked my computer and sure enough I had a beautiful
trace! It is now posted to PSN ....we get excited in
Texas if we get to use our "REGIONAL" tables!
-Charlie
At 11:50 AM 6/1/97 +1200, you wrote:
>Charlie and Co,
>
> Haven't heard from any of you.... Did any of you guys
>record the M3.4 Near Dallas a day ago ???
>
> Dave
> Dave A. Nelson
>
> 24 Jensen St.,
> Green Is., Dunedin,
> South Is.. New Zealand.
>
>http://psn.quake.net/dave/home.htm
>
>
>Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
>Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
> THE DIRECTION OF THE MOST DAMAGE
>Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
_ ________________________________________________ _
/ ) | | ( \
/ / | Charlie Thompson WB4HVD | \ \
_( (_ | _ e-mail: ct@....... _ | _) )_
(((\ \> |/ ) http://www.onr.com/user/ct/ct.html ( \| </ /)))
(\\\\ \_/ / Latitude 30.112 N \ \_/ ////)
\ / Longitude 97.891 W \ /
\ _/ Seismic Station .BUE \_ /
/ / |________________________________________________| \ \
/ / \ \
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Mark Wilson mark@.............." <wilsonm@............>
Subject: Re: Hall effect sensor.
Date: Sun, 1 Jun 1997 11:14:08 -0700 (PDT)
On Sat, 31 May 1997, Barry Lotz wrote:
> Mark Wilson mark@.............. wrote:
> >
> > On Sat, 31 May 1997, Barry Lotz wrote:
> > I messed around with a hall effect transducer a few years ago on my
> > leahman.
> >
> > Hall effect Switches are just that, switches.
> > Hall effect Transducers are linear devices. You can get them from
> > many sources. I got mine from Newarks Electronics.
> >
> > Hope that helps...
> >
> > > Norman Davis WB6SHI wrote:
> > > >
> Thanks Mark
> I'll check some sources. It seems the unit would be smaller than
> variable air caps and coils if they have reasonable sensitivity. The
> only disadvantage to me is measuring acceleration via displacement is
> not as "nice" as velocity via a coil.
> Barry
>
Oh, they are small, about 1/3 the size of a postage stamp and about
1/16" inch thick.
They are VERY senisitive
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Michael Chang <pya_cha@..................>
Subject: Interesting science projects
Date: Sun, 01 Jun 1997 18:10:32 -0700
For those of us interested in scientific DIY projects, here's a site that
might catch your interest.
http://www.best.com/~funsci/texts/index.htm
Michael Chang, Montreal Canada
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: what a blast of activity
Date: Mon, 02 Jun 1997 14:44:19 +1200
Hi all,
The last 7 days have been the busiest in the last 5 months.....
in 7 days I have recorded 14 events it all started with that M7 ++ in the
Kermadecs a week ago it seems to have induced a burst of activity all over
the New Zealand region.
over the last 5 months recording on avg. 1 event / 2-3 weeks this was
somewhat below the normal long term avg. of 1 event / 6 days. This
activity has done a lot to restore the avg recorded event numbers.
I have only posted the more interesting looking events to the PSN EVENTS
list
Cheers Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
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From: TESMECO@.......
Subject: Re: what a blast of activity
Date: Sun, 1 Jun 1997 23:11:00 -0400 (EDT)
does new zealand have a lot of quakes ?
and what kind of a magnitudes ?
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From: Benjamin Boozer <bbb3@..............>
Subject: Re: Hall effect sensor.
Date: Mon, 2 Jun 1997 12:04:23 -0400
On 5-31-97 Barry wrote:
"I however read a note to this site from Benjamin Boozer on
5/17/97 who talked about Hall Effect sensors. I haven't followed up on
it.
Any input Ben? =
Are the sensors linear? subject to more noise than coils? are there
crossover errors? where does one get data sheets or info on the sensors?"=
My Brief experience so far has been with the Honeywell SS94A1F. If anyone=
is interested in Hall Effect Transducers I highly suggest that they call
Honeywell 1-800-537-6495 USA and request their Solid State Sensors guide=
=2E
It has a wealth of info on sensors and how to use them in position sensin=
g
applications. I guess one of the problems in using HETs in seismographs i=
s
that they are position sensitive (might make a good tiltmeter?). =
There are several other things you should note about HETs. They are light=
and temperature sensitive. Avoid wide temp. variations and cover the sens=
or
with electrical tape. The output signal is based on the supply voltage, s=
o =
It should be WELL regulated. The SS94A1F draws about 15ma. of current and=
there is no need for fancy shielded cable in wiring the HET.
The HET is linear over a small range only. The best magnet arrangement I
have found is a bipolar slide-by with one magnet. Orient the magnets pole=
s
in the direction of movement. The magnet should be close (approx 1mm) and=
parallel to the HET. When the HET is centered between the poles, the outp=
ut
voltage will be 1/2 the supply. As the magnet moves, one pole will become=
closer thereby causing the output to go toward gnd. or the supply. The
thickness (?) of the magnet determines the sensitivity. I am using some
rare earth magnets from Radio Shack which are 1/16" thick. Using a 10v
supply, the output will swing from about .5v to 9.5v (page 75 of the
Honeywell guide).
As far as amps. go, I have used the AD620 Instrumentation Amplifier.
(Jameco Electronics). It's nice because it only uses one external resisto=
r
to set the gain from one to 1000. Leaving the resistor off will give a ga=
in
of one. To get a bipolar output, I create a voltage divider out of two
4.53K .1% resistors and a 10 turn 500 ohm pot (Mouser Electronics). One
resistor is attached to +v and the other to -v. The pot is connected
between them with the wiper going to +in (pin 3) on the AD620. The output=
from the HET goes to pin 2. Turn the pot to about 250 ohms (5 turns).
Physically adjust the magnet till it is as close to center as possible (0=
volts out from the amp). Adjust the pot to fine tune the adjustment. Use =
a
5 volt bipolar supply to power the amp and the HET. Connect +5v to the +v=
on the HET and -5v to gnd. on the HET. This will give a nice +/- output
from the amp.
I have not yet built a seismograph, but I have used the HET to make a
microbarograph sensitive to microbar changes in air pressure.
I hope the info is helpful.
Ben Boozer
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From: roger baker <rcbaker@........>
Subject: Re: Hall effect sensor.
Date: Mon, 2 Jun 1997 12:47:27 -0500 (CDT)
Friends,
I too have had experience with the little Hall effect
transducers that I think Benjamin is talking about. These are the ones
that the Scientific American article used to study insect respiration a
year or so ago, right? If so, they are indeed light sensitive and are
also little current hogs at 5 volts, which means that they may become
unstable due to slight thermal convection. I decided it would be nice to
use a pair of them in a bridge to detect field differentials and this worked
and will
detect a ceramic magnet a foot or so away, but the best arrangement might
be to mount two of them on some good heat sink like an aluminum bar. The
British electronics Mag (is it Electronics World?) had a few articles
within the last year on what sound like very similar devices but without
much thermal drift at all, which seems to be the chief source of noise, so
the latter sound better.
But my own experience has been that the problem with magnetic fields is
that they tend to be quite nonlinear and tend to interact as the cube of
the distance far apart and linear very near. I prefer optical and
capacitative sensors except when you can't control the axis of movement
very well, such as when measuring the respiration rate of a small insect.
I am using an interesting optical sensor to detect the small displacement
of a seismometer beam. All it is is a red laser pointer beam bouncing
back and forth between two dime store back surface mirrors giving a hall of
mirrors effect with five bounces between two coplanar mirrors before the
beam emerges into the displacement detector, which is a phototransistor
bridge. I use a little shiny aluminum wedge as a beam splitter. Of course
the multiple bounces greatly magnify any angular displacement of one of the
mirrors relative to the other.If you want the very best displacement
sensitivity, go to capacitative sensing which will be a little more work
to implement.
To give a very brief progress report, I have a nice little seismometer
project underway using the optical detector described above and with a
magnetic suspension, which apparently needs to be shielded for stability,
which means it needs to be enclosed in iron. Thus I am thinking in terms
of burying the seismometer in a sealed soft iron box as a typical field
application.
On the topic of microbarometers, my glycerine column device works quite
well and is reasonably stable. I have it all mounted with batteries inside a
camping-type plastic ice chest. The microphone is on the outside so it
gives of a low whine all the time, and all I have to do if it goes out of
range is to tilt the ice chest slightly with a little wedge under one side.
Many times the tone is quite stable, indicating a lack of strong weather
activity nearby, but in the case of storms like we have had in the Austin
area recently, the pitch constantly shifts like an irregular siren. The
sensitivity of the device is such that it shifts in tone when you
compress air slightly by walking down a hallway leading into the room
where the device is situated. I know thats a pretty dumb way to judge
sensitivity, but there it is for whats its worth. Obviously these devices
beg to be tied together in arrays so that the sound sources can be located.
--Yours, Roger
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From: ACole65464@.......
Subject: Microseismometers
Date: Tue, 3 Jun 1997 01:06:00 -0400 (EDT)
Greetings PSN,
I recently read an article in the June 97 edition of the Final Frontier, a
magazine for science, though mostly about outer space. In it was an article
describing the array of new minaturised instruments that NASA is developing
for future deployment on other planets, i.e. Mars. They are planning to send
smaller spacecraft, but more of them, to a given planet. Placed on-board will
be some very small seismometers. I managed to find a more in-depth
description, with photos, of the seismometers at the home page of the "Center
for Space Microelectronics Technology", a group at JPL.
Check out how small they really are, I hope that they (more likely a licensed
manufacturer) will mass produce it so we all can afford one. The performance
rivals an STS-2 seismometer. See the comparsion test results on their Web
page. At least this is getting closer in size though not cost to the
"jellybean" seismometer concept. Please follow the directions below to the
description.
Web page:
http://mishkin.jpl.nasa.gov/newcsmt.html. Then select CSMT Technology, then
Microseismometer and Micro acclerometers.
Bye for now,
Allan Coleman, Seattle
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From: Norman Davis WB6SHI <normd@.............>
Subject: Re: Hall effect sensor.
Date: Sun, 01 Jun 1997 08:50:23
At 09:36 AM 5/31/97 -0700, you wrote:
>Mark Wilson mark@.............. wrote:
Thanks guys, will think this over and get the gate working first then maybe
play with het later.
Norman Davis WB6SHI
Email normd@.............
Shingle Springs, Ca, USA
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From: Edward Cranswick <cranswick@........>
Subject: Microseismometer and Microaccelerometers
Date: Tue, 03 Jun 1997 12:13:51 -0600
Thomas-
I am a seismologist for the USGS who chases earthquakes -- investigates
aftershock sequences of destructive earthquakes with portable
seismographs, and I think you website about, "Microseismometer and
Microaccelerometers", is very interesting. We don't have cheap,
reliable mass-produced sensors to record ground motions on Earth, let
alone Mars. I was referred to your site from a mail server of the
Public Seismic Network <http://psn.quake.net/>. I am forwarding an
article we wrote for AGU's Eos five years ago about "Recording Ground
Motions Where People Live". I would like to know what you estimate the
cost of the JPL microseismometer would be if it were mass-produced in
quantities of a hundred thousand a batch?
-Edward
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
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From: Edward Cranswick <cranswick@........>
Subject: Re: PSN Donations
Date: Tue, 03 Jun 1997 15:42:06 -0600
Roger-
Roger Sorensen wrote:
>
> Do you know if PSN donations are tax deductable?
I don't believe that PSN deductions are tax deductible, but I believe
that Dorothy Darby looked into this a few years ago.
>
> Thanks,
>
> Roger
>
> P.S. I'm the one in Chatsworth that has the ADXL05 sensor. You were
> right (was there any doubt?), it takes a strong quake to get a
> good signal out of it. My sensor runs with the equivalent of about
> 7%g of noise. The 5.0Mb Northridge aftershock a couple months back only
> produced 13%g here (about 8-9 miles away). It's too bad it's so
> noisy and insensitive. I was really looking forward to having all
> three dimensions. I'm working on a single axis short-period Lehman
> now.
I am sorry to hear that you didn't get a good record, but you did get
something. In my experience, it is after one tries to record an actual
earthquake that all the problems become clear. Is there any possibility
that you could reduce the noise of the ADXL05? I think that it is an
important matter to pursue.
>
> P.P.S. Do you have any recommendations on elementary level textbooks
> that discuss the analysis of siesmographs? (or is that too advanced?)
Not having used them myself (though I wish I had when I taught an
introductionary class at the American University of Armenia on the
digital recording/analysis of strong ground motions that acted as a
warm-up for a seismology class that Bolt subsequently there), but
Professor Bruce Bolt has written several introductory texts on the
subject that I understand to be excellent. Others in the PSN should
know.
-Edward
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
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From: Edward Cranswick <cranswick@........>
Subject: Re: Displacement data
Date: Tue, 03 Jun 1997 16:00:54 -0600
Bob-
In general, you should address your questions to the PSN list as a
whole, because on many issues, I am profoundly ignorant.
With respect to the displacement, Larry has a new version of WinQuake
out that allows one to integrate a velocity trace to displacement. You
could use that to make whatever comparisons. Since it is relatively
easy to calculate a displacement record from a velocity record, but
moving the datamass of the original timeseries is the killer, the USGS
generally makes available only one flavor of ground motion. Hovever, in
the case of the traditional strong motion accelerometer (SMA) records
which are recorded on analog 35 mm film, the digitized data are released
as acceleration, velocity, and displacement after suitable processing to
remove artifacts of this old instrumentation.
-Edward
Bob Lewis wrote:
>
> I did some experimenting over the weekend with the mass-position sensor that is
> part of my Geotech 8700C LP horizontal seismometer. I found that, with only a
> small amount of amplification, that DATA is on the mass-position output, from
> the photoelectric sensor inside the unit. There is no noise present, and the
> level is quite high. I plan to amplify this data and experimentally record it
> as another input to my A-D board. I currently have conventional long-period
> velocity data as my main trace. I suspect that I will have to high-pass filter
> the data, or changes in the mass position will eventually put the trace off the
> screen.
>
> This brought up a question in my mind: What will displacement data look like
> compared to velocity data? Are there any USGS Web sites that might have
> velocity and displacement data available for viewing side-by-side, for the same
> event?
>
> This little experiment was to look into different possibilities to sense mass
> position that will be needed for a force-balance conversion. I have a Geotech
> 4681A "Baby Benioff" short-period vertical that I think would be a good
> candidate for conversion. I have a linear hall-effect sensor on order, inspired
> by an Amateur Scientist article where one was used to sense micron-level
> motion. I just thought I would also look at an optical method, and I was very
> surprised to see that data was present on the very simple mass-position sensor.
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
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From: David Wolny <dwolny@.......................>
Subject: Re: PSN Donations
Date: Wed, 4 Jun 1997 09:26:04 -0600 (MDT)
On Tue, 3 Jun 1997, Edward Cranswick wrote:
> Roger Sorensen wrote:
snip> >
> >
> > P.P.S. Do you have any recommendations on elementary level textbooks
> > that discuss the analysis of siesmographs? (or is that too advanced?)
>
> Not having used them myself (though I wish I had when I taught an
> introductionary class at the American University of Armenia on the
> digital recording/analysis of strong ground motions that acted as a
> warm-up for a seismology class that Bolt subsequently there), but
> Professor Bruce Bolt has written several introductory texts on the
> subject that I understand to be excellent. Others in the PSN should
> know.
> -Edward
>
> --
> Edward Cranswick Tel: 303-273-8609
> US Geological Survey, MS 966 Fax: 303-273-8600
> 1711 Illinois St cranswick@........
> Golden, CO 80401 USA E.M. Forster said, "Only connect".
>
> __
Roger
Besides Bolt's books, you might also try; "Earthquake Interpretations; A
Manual For Reading Seismograms". Author; Ruth B Simon, Woodward-Clyde
Consultants, pub. William Kaufmann, Inc., Los Altos, Calif, 1981.
I'm not sure how hard it will be to find, but it offers a good basic
analysis of seismograms.
Dave Wolny
Mesa State College
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From: roger baker <rcbaker@........>
Subject: Jellybean report
Date: Wed, 4 Jun 1997 12:25:26 -0500 (CDT)
Friends,
I got a little cheap easy to build force balance
vertical axis seismometer working, although Im in the early stages of
figuring out all the design tradeoffs. Since a text byte is worth a
thousand bytes of graphic file, so I will describe a few details as a
little progress report that might give useful ideas to others.
(I would like very much, incidently, to know whether the Jet Propulsion
Lab miniature seismometer uses a high vacuum to increase the Q of its
beam and thus get its good performance in a small package. Anybody
know?).
About all my seismometer is in its current incarnation is a razor blade
resting on a sheet of soft metal that has magnets on the other side to
hold the edge against the metal like aluminum or brass and make a nearly
frictionless pivot. Then you attach a mirror and ceramic magnet to the
razor blade and put a largeish opposing ceramic magnet under the now
horizontal blade to push it up horizontal against the force of gravity.
I use a cheap laser pointer and five or six light bounces between two
coplanar
mirrors, one being the one mounted on the pivoting blade, and the other
just over it to detect deflection of the little beam. Multiple bounces
gives very high deflection detection sensitivity. A single radio Shack
phototransistor in series with about 100 k ohms is enough to detect the
exact position of the emerging beam well enough. The photodiode is glued
against a piece of ground glass that slides along a plane and can be
positioned easily under a spring clamp to get it in optimum position
while watching my scope.
The beam is not much bigger than the razor blade, since it not much else
than a razor blade. The goal is to make the beam physically small but
give the beam a very high Q. Once disturbed, magnetically suspended beams
will continue to swing for as much as ten minutes before coming to a
rest, equaling several thousand oscillations, meaning that the system has
a very high Q. Who knows how much more this could be increased by
surrounding the beam with a high vacuum?
One can adjust the magnetic suspension to give nearly any stiffness or
restoration force, and thus the period of the beam may be easily varied
between perhaps 20 hertz down to one second or so, the latter when the
magnetic field is made very linear and equal in its force to gravity.
When the magnetic force is very nearly equal and opposite to the force of
gravity, you are getting a lot of beam deflection per unit of kinetic
energy added into the system, which is generally good.
Longer periods are hard to achieve, but short periods with good stability
are achieved by mounting strong magnets that repel the magnet on the beam
from either side. Anyone who has hung a nail from a magnet by its point
and watched it swing a long time will understand that these little
magnetic suspension oscillating systems with a mass of few grams have low
loss and high Q. In fact the most sensitive detector might be an array of
little tuned beams spanning the frequency spectrum like the channels of a
sound spectrograph. But since the system has a period of a fraction
of a second, we need to use force balancing to lengthen it. Force
balancing is easy to achieve, but hard to optimize, with a flat copper
coil mounted near the little ceramic magnet on the beam. The coil is
wound wet with epoxy so that after the epoxy cures, it can be positioned
easily.
The circuit is very simple at present, being entirely made of four 324 op
amps with paralleled outputs to get a few hundred milliwatts of power.
When the feedback loop is working properly, the beam appears to be quite
stationary (you can see any minute movement in the speckle pattern
produced by the beam in the area where the beam hits the ground glass.
Despite the fact that the beam now LOOKS stationary, the oscilloscope
reveals that there is a low level DC restoration current feeding back
magnetic force to keep it that way. This resoration force may be seen to
extend to DC by bring a magnet near to the instrument, thus changing the
constant force on the beam.
The power supply is a six volt lead acid battery right now. My feedback
is operated to either side of a virtual ground at three volts. In other
words the can attract or repel by swing its supply a few volts to either
side or a virtual ground. The coil is a few cm in diameter has a DC
resistance of ten ohms, and is probably a few hundred turns of #30 wire.
At this early stage of design, I have not tamed back the feedback loop (I
flunked servo design 101). Thus the system is only stable with the
feedback voltage into the coil greatly weakened by putting a resistor in
series. Im not very good at Bode plots and Nyquist diagrams, which is
whats needed to really optimize the system design so it stays steady as a
rock when the biggie hits.
Part of the personality of the current system is that the characteristic
period of the beam is considerably damped by feedback but still dominates
as noise. I live near a freeway with a lot of truck traffic, and Im
seeing a constant background of such noise at the five hertz resonant
frequency of the beam. I understand that one way to help tame feedback
oscillations is to put in a notch filter tuned to the resonant frequency
of the system in the feedback loop.
One design goal has been to mininimize the size of the instrument so that
temperature control and magnetic shielding will be easier. Right now, the
biggest dimension of the instrument is the vertical pencil-like laser
pointer.
--Yours, Roger Baker; Science Hacker
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From: Edward Cranswick <cranswick@........>
Subject: [Fwd: Re: CNSS meeting]
Date: Wed, 04 Jun 1997 16:43:07 -0600
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
I was looking at Article 1, Section 4, "Eligibility". I read "although membership is
restricted to institutions and agencies of the United States engaged in seismic
operations therein, all individuals and groups engaged in relevant efforts are welcome
and encouraged to participate in the work of the Council. Affiliate memberships may be
considered for domestic and foreign organizations."
I took "institutions and agencies of the United States" to mean U.S. Government
Agencies. "Affiliate memberships may be considered for domestic and foreign
organizations." What is the difference between an "institution and agency" and an
"organization"? Which category, if either, would we fit in? This paragraph, to me,
seems to have such nebulous wording that it could be interpreted in several ways,
depending on who's reading. "Individuals and groups" are "encouraged to participate in
the work of the Council", but these "individuals and groups" do not seem to eligible for
membership, unless it is under the "domestic and foreign organizations" category. See
what I mean? It looks like, unless you are a "member", your efforts would not be
officially recognized, and you would not have a "voting representative".
I certainly think that we ARE "engaged in sustained operation of networks of
instruments that record ground motion". The membership list has 23 state universities,
plus National labs and State organizations, and the Geological Surveys. The USGS, quite
properly, will serve as the "Steward" and "Secretariat". Is the Deleware Geological
Survey, for example, a state agency and a member of USGS, or are they just a state
agency?
From: Jim Hannon <jmhannon@........>
Subject: Re: Microseismometers
Date: Wed, 04 Jun 1997 17:56:40 -0500
ACole65464@....... wrote:
>
> Greetings PSN,
> I recently read an article in the June 97 edition of the Final Frontier, a
> magazine for science, though mostly about outer space. In it was an article
> describing the array of new minaturised instruments that NASA is developing
> for future deployment on other planets, i.e. Mars. They are planning to send
> smaller spacecraft, but more of them, to a given planet. Placed on-board will
> be some very small seismometers. I managed to find a more in-depth
> description, with photos, of the seismometers at the home page of the "Center
> for Space Microelectronics Technology", a group at JPL.
> Check out how small they really are, I hope that they (more likely a licensed
> manufacturer) will mass produce it so we all can afford one. The performance
> rivals an STS-2 seismometer. See the comparsion test results on their Web
> page. At least this is getting closer in size though not cost to the
> "jellybean" seismometer concept. Please follow the directions below to the
> description.
> Web page:
> http://mishkin.jpl.nasa.gov/newcsmt.html. Then select CSMT Technology, then
> Microseismometer and Micro acclerometers.
> Bye for now,
> Allan Coleman, Seattle
>
> The most recent issue of Electronic Design Mag. May 27, 1997 has an article on this and other similar sensors. It seems to h
ave a little more detail on how it works. There is also an ad in the same Mag. for Variable Capacitance Accelerometer by Endev
co. I am not sure I believe the price quoted, $3.50 each in production quantities.
--
Jim Hannon
http://soli.inav.net/~jmhannon/
42,11.90N 91,39.26W
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From: "Charles R. Patton" <patton@..........>
Subject: Re: Microseismometers
Date: Wed, 04 Jun 1997 17:10:29 -0700
As a follow on to the "jellybean seismometer", you can also look at the
Northeastern University (who helped JPL make the micro-accelerometers)
site in the engineering dept:
http://www.ece.neu.edu/edsnu/zavracky/mfl/programs/acc/acc.html
This contains a very detailed description of the design along with
references.
With regard to Roger's(?) question, "..do they vacuum enclose the
mass?" It doesn't appear that they do, as it is a force balance style
device with a tunneling electron tip sense of the mass position.
Anyway, check out the URL above for more information, if you're
interested.
Charles R. Patton <patton@.........>
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From: ACole65464@.......
Subject: Background Seismic Noise, How Much is TOO Much
Date: Wed, 4 Jun 1997 22:55:43 -0400 (EDT)
Dear PSN member,
Do you know what the typical background noise levels are for where your
seismometers are sited? I am curious in knowing how many of you have gone
through this exercise to calculate what the average levels that you record.
Using the Bob Barnes seismo calibrator (description posted on the PSN Sept
12th 1996), but with slight design tweaks, it was possible for me to
determine the sensitivity of my home-made force-feedback accelerometer and so
with that known, I calculated what the noise levels were at my site in a
surburb north of Seattle. The normal quiet day saw ground accelerations of
<20 nanometers and when trains go by (1 mile away) every couple of hours then
the accelerations jump up to 400 - 600 nanometers for a couple of minutes,
then drop to normal levels again. On really quiet days I have seen <10
nanometers as the norm. During stormy windy days the levels are >40
nanometers. To prevent the recorder being overworked I have a 2nd order high
pass filter with a corner frequency of .03 Hz to limit the seismometer's
output.
I contacted a seismologist at the University of Washington some time ago,
asking him as to what the "average" levels would be acceptable for an urban
site. He told me the following:
No more than 10**-5 g (peak to peak) for the average suburban site.
10**-4 g is considered too noisy.
10**-3 g is the range for small felt earthquakes.
The Princeton PEPP program says 100 nanometers max for there sites. I would
like to hear from others regarding these numbers. Do they sound reasonable?
Allan Coleman, Seattle
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From: "Charles R. Patton" <patton@..........>
Subject: Re: Microseismometers
Date: Thu, 05 Jun 1997 09:34:11 -0700
Jim Hannon wrote:
>...Electronic Design Mag. May 27, 1997...
>There is also an ad in the same Mag. for Variable Capacitance Accelerometer
>by Endevco. I am not sure I believe the price quoted, $3.50 each in production >quantities.
I saw the same article, got excited and went to their (Endevco's) web
site and pulled down the specs for the parts mentioned - the 7591 and
7592. The excitement was quickly quenched. Unfortunately the quoted
"threshold resolution" is 0.0005 equivalent g's for the +-2 g units
where the definition is:
threshold = (max.residual noise from 0.5 to 100 Hz) / sensitivity
So, so far the Humphrey unit is still the winner, unless we can get our
hands on some of the JPL/Northwestern University microseismometers whose
quoted sensitivities are in the range of 10^-8 g's. Unfortunately, even
as much as I think they're neat, my practical experience says that it
will be years before any commercial quanitities might be available.
Charles R. Patton <patton@.........>
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From: Robert L Barns <75612.2635@..............>
Subject: Snowballs from space
Date: Thu, 5 Jun 1997 13:56:22 -0400
Hi gang,
The confirmation (reported last week) about the snowballs from space
which strike the very top of earth's atmosphere is fascinating. For thos=
e
who have not seen this report--a satellite UV camera seems to have detect=
ed
objects (perhaps 20,000/day) weighing perhaps 20 tons each which
disintegrate at very high altitude (say 300 miles). These objects are
thought to be mostly water ice. If this has been going on since early in=
the earth's life, it could account for all the water on the earth.
One of the objections to this finding which I find most persuasive is
that the seismometer still operating on the moon does not seem to detect
collisions between the moon and these objects.
I'm curious about the characteristics of the seismometer on the moon. =
Can anyone suggest where to find some info on this?
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Lloyd Verhage" <verhage@.............>
Subject: Re: Snowballs from space
Date: Thu, 5 Jun 1997 14:18:17 CST6CDT
> Hi gang,
> The confirmation (reported last week) about the snowballs from space
> which strike the very top of earth's atmosphere is fascinating. For those
> who have not seen this report--a satellite UV camera seems to have detected
> objects (perhaps 20,000/day) weighing perhaps 20 tons each which
> disintegrate at very high altitude (say 300 miles). These objects are
> thought to be mostly water ice. If this has been going on since early in
> the earth's life, it could account for all the water on the earth.
> One of the objections to this finding which I find most persuasive is
> that the seismometer still operating on the moon does not seem to detect
> collisions between the moon and these objects.
> I'm curious about the characteristics of the seismometer on the moon.
> Can anyone suggest where to find some info on this?
> Bob Barns
Just a comment (nothing personal), NASA shut off the ALSEPs (which
included the lunar seismometers) back in the late 70's for budget
reasons. There have been no working seismos on the Moon since then
(to our loss).
But in the past, no icy impacts of that magnitude were detected. It
may be that they break up before striking the Moon (perhaps when they
pass within the Roche limit). I'm curious to see the resolution of
this question myself.
Lloyd
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Microseismometer and Microaccelerometers
Date: Thu, 5 Jun 1997 13:56:26 -0400
Ed,
I will be most interested to see the reply to your query about a
mass-produced seismometer.
Is it likely that a rig for Mars will be suitable for a 'peoples'
seismometer? I would think that a 'peoples' seismometer would be a shor=
t
period high acceleration device while the one for Mars would be a long
period device with maximum sensitivity. =
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Winquake
Date: Thu, 05 Jun 1997 13:03:09 -0700
Hi Bob and others,
I have been working on a new version but have not had the time to make a
official release. I did send a beta release (both 16 and 32 bit) to the
guys at the PEPP.
Bob Clouser placed the two zip files on their system at:
http://lasker.princeton.edu/Programs/pc.html
If you want to play around with it you can download it from there or from:
ftp://www.drnet.com/users/psn/software/wq16beta.zip for the 16 bit
version or ftp://www.drnet.com/users/psn/software/wq32bets.zip for the 32
bit version.
The zip files only contain the new exe and some updated dat files. You will
need to copy the files from your temp directory over to your working
WinQuake directory because I don't have a install/setup program ready yet.
Also missing are any doc files, so heres what's new:
WinQuake will now do the intergration of the data. You will see a new Tool
Bar icon with a "I" in it or you can use the View/Intergate menu.
I also added Md (coda) magnitude calculation. This uses the duration rather
then max amplitude to calc magnitude. It works on the fact that the bigger
the event the longer the event will last or show up on the seismogram. This
is ONLY useful for local events that are recorded on short period sensors.
The last new feature is a list of directories under the File menu. As you
change to other directories using the File Open/Directory dialog box a list
of used (max of 8) directories will show up under the File menu. This way
you can move to other directories where event files are stored more easily.
That's it, enjoy...
Regards,
Larry Cochrane
Redwood City, PSN
At 07:37 AM 6/4/97 -0700, Bob Lewis wrote:
>I understand that you have a new version of Winquake that allows you to
convert
>(integrate?) acceleration/displacement to velocity and/or vice versa. Or
does
>the Version 2.3 that I'm using now do this and I just don't know it?
>
>I have two machines running Windows 3.1, one running Windows for Workgroups,
>and one running Windows 95. I don't know if this new version is 32 or 16
bit.
>
>Please let me know where I can download this.
>
>Thanks...
>
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Snowballs from space
Date: Fri, 06 Jun 1997 11:51:36 +1200
Lloyd
the seismometers that were placed and operating on the moon
between Nov. 1969 qnd Sept. 1977, detected moonquakes attributed to 3
causes. Impacts, Shallow ... 0-60km depth, and deep 600-900 km depth.
the deep ones seemed to come from a limited number of foci ~50 that are
on the infered mantle - core boundary. The seismograms of different
events from the same foci are almost identical with each other and each foci
becomes active at some definite time each month. This tidal forces are the
cause. There are peaks of activity 14 days apart and secondary peaks at 206
day intervals which would coincide with the Sun's contribution to the tidal
forces.
the shallow events are thought to result from the release of crustal
stresses. Only about a dozen of these events were recorded and no obvious
patterns were seen.
Moonquake seismograms are quite different from terresterial ones. The
movements are much higher in freq., and reveberation continues for a very
long time .... for the shallow and deep events up to 50 minutes and for
impacts... well in excess of an hour for the larger ones.
It was hard to pick phases and there were no clear surface waves, the very
dry lunar surface is thought to be responsible.
The crust was found to have an avg. P - velocity of ~6.7km/s and the
mantle has a fairly uniform p vel. of ~ 8 km/s
Who knows whether the impacts on the moon that were recorded were solid or
icy objects!!!
BTW a seismograph was landed on Mars in Nov. 1976 on the Plains of Utopia,
by the Viking spacecraft and only one undisputable event was recorded in the
546 days of operation and it was an event of about M6.
when I get time I will add some graphics to my web page to show some
seismograms and the infered internal structure of the moon..
Must get away and do some more exam study...
DAve N.
>
>But in the past, no icy impacts of that magnitude were detected. It
>may be that they break up before striking the Moon (perhaps when they
>pass within the Roche limit). I'm curious to see the resolution of
>this question myself.
>
>Lloyd
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Clark Wockner <clark@.............>
Subject: quake???
Date: Thu, 05 Jun 1997 19:17:07 -0700
Hi Guys:
Did any one record a good trace around 22:51 utc???
Just a beginner here. But, It looks like I have a good trace here in
Illinois.
Clark
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: [Fwd: Re: PSN Donations]
Date: Thu, 05 Jun 1997 21:39:17 -0600
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
From: Charlie Rond <rond@................>
Subject: St. Agnes High School seismo works!
Date: Fri, 06 Jun 1997 05:12:18 -0500
Larry,
Got everything hooked up today at St. Agnes High School and it all works!
It's an amazing experience to hook up your electronics (A/D card;
amp/filter; power supply; coil) and have them work the first time! Mighty
good work you do.
The unknown, of course, will be how it responds in a classroom building,
with student activity, and major streets a hundred yards away on two sides.
But after an initial period of "pegging" - and after adding a large
compression factor - the trace flattened out and gave a nice little "quake"
with a carefully calibrated foot stomp :-)
Hopefully, will be completing Ridgeway High School's system within the next
few days.
School is ending - we won't really get to see student monitoring until the fall.
And Biology prof, Toni Brautigan, who has provided wonderful support during
the long assembly process, is moving to Arizona :-(
I wonder if you - or Steve Hammond - or Ken may have assembled documentation
which could form a core handbook/manual for St. Agnes and Ridgeway High Schools?
Thanks for your help! And thanks, also, to Edward Cranswick for launching
us, and Steve Hammond, for building our foundation.
Charlie Rond -\/\--Public Seismic Network-Memphis
rond@................ (901) 360-0302 [ free BBS ]
http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Background Seismic Noise, How Much is TOO Much
Date: Fri, 06 Jun 1997 09:40:12 -0600
Allan-
I think your post about seismic noise levels is very interesting. I am
confused by your giving noise estimates from your accelerometer in
nanometers, i.e., in units of displacement rather than acceleration.
The values cited by the UW seismologist seem reasonable to me. However,
sometimes strong motion instruments must be run in noisy environments,
greater than 10**-4 g, because it is important to monitor strong ground
motions at these sites for the same reason that they are noisy: there
is a very strong site response caused by low-velocity unconsolidated
surficial sediments that amplify the vibration produced by critical
facilities or high population densities in the area.
We, the USGS, have a large body of noise information from urban areas
but our database situation is out of control; one of these days we
might be able to put some statistics together.
-Edward
ACole65464@....... wrote:
>
> Dear PSN member,
> Do you know what the typical background noise levels are for where your
> seismometers are sited? I am curious in knowing how many of you have gone
> through this exercise to calculate what the average levels that you record.
> Using the Bob Barnes seismo calibrator (description posted on the PSN Sept
> 12th 1996), but with slight design tweaks, it was possible for me to
> determine the sensitivity of my home-made force-feedback accelerometer and so
> with that known, I calculated what the noise levels were at my site in a
> surburb north of Seattle. The normal quiet day saw ground accelerations of
> <20 nanometers and when trains go by (1 mile away) every couple of hours then
> the accelerations jump up to 400 - 600 nanometers for a couple of minutes,
> then drop to normal levels again. On really quiet days I have seen <10
> nanometers as the norm. During stormy windy days the levels are >40
> nanometers. To prevent the recorder being overworked I have a 2nd order high
> pass filter with a corner frequency of .03 Hz to limit the seismometer's
> output.
> I contacted a seismologist at the University of Washington some time ago,
> asking him as to what the "average" levels would be acceptable for an urban
> site. He told me the following:
> No more than 10**-5 g (peak to peak) for the average suburban site.
> 10**-4 g is considered too noisy.
> 10**-3 g is the range for small felt earthquakes.
> The Princeton PEPP program says 100 nanometers max for there sites. I would
> like to hear from others regarding these numbers. Do they sound reasonable?
> Allan Coleman, Seattle
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Microseismometer and Microaccelerometers
Date: Fri, 06 Jun 1997 09:59:42 -0600
Bob-
Not knowing the details of the design and manufacturing process, I
simply assume that the developments in technology will produce a sensor
for a "peoples seismic array" with strong motion capability (recording
acceleration from +/- 10**-5 to 2.0 g) to record large local earthquakes
on-scale but which can also effectively record nanometer-level
displacements from teleseisms to keep people interested in between the
significant local events. Perhaps this will require two distinct
sensors which could nonetheless be packaged together.
-Edward
Robert L Barns wrote:
>
> Ed,
> I will be most interested to see the reply to your query about a
> mass-produced seismometer.
> Is it likely that a rig for Mars will be suitable for a 'peoples'
> seismometer? I would think that a 'peoples' seismometer would be a short
> period high acceleration device while the one for Mars would be a long
> period device with maximum sensitivity.
> Bob Barns
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.......>
Subject: Re: Background Seismic Noise, How Much is TOO Much
Date: Fri, 06 Jun 1997 09:15:16 -0700
On Wed, 4 June 1997 22:55:43 Allan Coleman wrote:
>Do you know what the typical background noise levels are for where your
>seismometers are sited? I am curious in knowing how many of you have gone
>through this exercise to calculate what the average levels that you record.
Allan --
I am curious about people's experience with this too. I'm not sure what
units of measure you want, but since the predominant background noise has a
period of about 6 seconds (approx. 2*pi), the magnitude of displacement,
velocity, and acceleration are about the same. I'll give it to you in
meters/second, since my output is a velocity output.
Given that, my noise level on a quiet day is about 500 nanometers/sec
peak-to-peak, rising to about 2000 nanometers/sec peak-to-peak on a noisy
day. There is a model of minimum earth noise that I've seen published (I
can't remember where right now), and my notes indicate these numbers are
reasonably consistent with that model.
As you can see, the noise level varies over a 4:1 range (sometimes more).
I live about 15 miles from the Pacific Coast, about 1 mile from light-rail
transit system tracks, and about 1 mile from a major freeway. I've never
seen any strong correlation with the rail or freeway traffic, but I've not
really studied it.
My soil type is listed on the geological map as granite rocks, and there
are numerous large outcroppings in the immediate area but none suitable for
seismometer mounting on this property :(
The noise level seems to be most related to storms and my guess is that it
is due to upper-level winds, although surf noise could be a factor. One
could try correlations using one of the microbarographs discussed here --
that would be interesting.
Karl Cunningham
La Mesa, CA.
karlc@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.......>
Subject: Unknown Long-period signal
Date: Fri, 06 Jun 1997 09:15:29 -0700
Greetings --
I've been experimenting with the long-period output of my force-balance
seismometer and saw an unusual very-long-period sine wave starting at about
2200 UT yesterday (6/5), that lasted for about a half hour.
It was fairly large -- acceleration about 700 nanometers/sec^2 (velocity
about 2e-5 meters/sec) -- with a period of about 200 seconds. This is at
least 20:1 above my instrument's noise level at this frequency, so I think
it was real.
Anybody know what this might be?
Karl Cunningham
La Mesa, CA.
karlc@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Greg Lyzenga <lyzenga@.................>
Subject: Re: Background Seismic Noise, How Much is TOO Much
Date: Fri, 06 Jun 1997 09:34:05 -0700
>I am curious about people's experience with this too. I'm not sure what
>units of measure you want, but since the predominant background noise has a
>period of about 6 seconds (approx. 2*pi), the magnitude of displacement,
>velocity, and acceleration are about the same. I'll give it to you in
>meters/second, since my output is a velocity output.
>
....
>As you can see, the noise level varies over a 4:1 range (sometimes more).
>I live about 15 miles from the Pacific Coast, about 1 mile from light-rail
>transit system tracks, and about 1 mile from a major freeway. I've never
>seen any strong correlation with the rail or freeway traffic, but I've not
>really studied it.
>
....
>The noise level seems to be most related to storms and my guess is that it
>is due to upper-level winds, although surf noise could be a factor. One
>could try correlations using one of the microbarographs discussed here --
>that would be interesting.
>
The 6-second microseisms that you mention here have been investigated for
many years, and it is pretty well established that they are caused by ocean
waves which exert pressure fluctuations of this frequency on the near-coast
ocean floor. I've got a couple of journal papers which contain the
analysis of this problem, although I haven't got the references handy at
this moment. If anyone's interested, I can look them up in the next day or
two. The topic is also probably discussed in Aki and Richards, come to
think of it...
- Greg Lyzenga
|Gregory A. Lyzenga <lyzenga@.................> *** (909) 621-8378
|Dept. of Physics, Harvey Mudd College *** fax (909) 621-8887
|Claremont, CA 91711-5990
http://www.physics.hmc.edu/profs/lyzenga.html
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Steve Hammond <shammond@..........>
Subject: Re: St. Agnes High School seismo works!
Date: Fri, 6 Jun 1997 09:35:54 -0700 (PDT)
Why to go, Charlie. That's great. I still have some old hardware; old XT
and AT class stuff, a few mono, color, and EGA displays, a couple of dot
printers, and a few 2400 baud modems sitting around. Need anything before
I give it away?
Regards, Steve Hammond PSN San Jose, California
On Fri, 6 Jun 1997, Charlie Rond wrote:
> Larry,
>
> Got everything hooked up today at St. Agnes High School and it all works!
>
> It's an amazing experience to hook up your electronics (A/D card;
> amp/filter; power supply; coil) and have them work the first time! Mighty
> good work you do.
>
> The unknown, of course, will be how it responds in a classroom building,
> with student activity, and major streets a hundred yards away on two sides.
> But after an initial period of "pegging" - and after adding a large
> compression factor - the trace flattened out and gave a nice little "quake"
> with a carefully calibrated foot stomp :-)
>
> Hopefully, will be completing Ridgeway High School's system within the next
> few days.
>
> School is ending - we won't really get to see student monitoring until the fall.
> And Biology prof, Toni Brautigan, who has provided wonderful support during
> the long assembly process, is moving to Arizona :-(
>
> I wonder if you - or Steve Hammond - or Ken may have assembled documentation
> which could form a core handbook/manual for St. Agnes and Ridgeway High Schools?
>
> Thanks for your help! And thanks, also, to Edward Cranswick for launching
> us, and Steve Hammond, for building our foundation.
>
>
>
>
>
>
> Charlie Rond -\/\--Public Seismic Network-Memphis
> rond@................ (901) 360-0302 [ free BBS ]
> http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
>
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Background Seismic Noise, How Much is TOO Much
Date: Fri, 06 Jun 1997 10:53:35 -0600
Karl-
You have made an excellent point about the importance of specifying the
frequency range of the noise. Because I have worked almost exclusively
with data recorded by portable autonomous digital seismographs, most of
my experience has been with seismic signals, including noise, at
frequencies greater than 1.0 Hz, i.e., periods less than 1 s.
-Edward
Karl Cunningham wrote:
>
> On Wed, 4 June 1997 22:55:43 Allan Coleman wrote:
>
> >Do you know what the typical background noise levels are for where your
> >seismometers are sited? I am curious in knowing how many of you have gone
> >through this exercise to calculate what the average levels that you record.
>
> Allan --
>
> I am curious about people's experience with this too. I'm not sure what
> units of measure you want, but since the predominant background noise has a
> period of about 6 seconds (approx. 2*pi), the magnitude of displacement,
> velocity, and acceleration are about the same. I'll give it to you in
> meters/second, since my output is a velocity output.
>
> Given that, my noise level on a quiet day is about 500 nanometers/sec
> peak-to-peak, rising to about 2000 nanometers/sec peak-to-peak on a noisy
> day. There is a model of minimum earth noise that I've seen published (I
> can't remember where right now), and my notes indicate these numbers are
> reasonably consistent with that model.
>
> As you can see, the noise level varies over a 4:1 range (sometimes more).
> I live about 15 miles from the Pacific Coast, about 1 mile from light-rail
> transit system tracks, and about 1 mile from a major freeway. I've never
> seen any strong correlation with the rail or freeway traffic, but I've not
> really studied it.
>
> My soil type is listed on the geological map as granite rocks, and there
> are numerous large outcroppings in the immediate area but none suitable for
> seismometer mounting on this property :(
>
> The noise level seems to be most related to storms and my guess is that it
> is due to upper-level winds, although surf noise could be a factor. One
> could try correlations using one of the microbarographs discussed here --
> that would be interesting.
>
> Karl Cunningham
> La Mesa, CA.
> karlc@.......
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: St. Agnes High School seismo works!
Date: Fri, 06 Jun 1997 11:48:06 -0600
Charlie-
Congratulations! The best thing that I could send you would be an
earthquake, but I haven't worked out how to do that yet.
-Edward
PS. Ted Blank deserves a great deal of credit for the PSN because if he
hadn't put together the software to turn a PC into a waveform
acquisition device, we'd never have gotten off the ground. I realized
the other day that I have been remiss in not referring to his critical
contribution.
Steve Hammond wrote:
>
> Why to go, Charlie. That's great. I still have some old hardware; old XT
> and AT class stuff, a few mono, color, and EGA displays, a couple of dot
> printers, and a few 2400 baud modems sitting around. Need anything before
> I give it away?
>
> Regards, Steve Hammond PSN San Jose, California
>
> On Fri, 6 Jun 1997, Charlie Rond wrote:
>
> > Larry,
> >
> > Got everything hooked up today at St. Agnes High School and it all works!
> >
> > It's an amazing experience to hook up your electronics (A/D card;
> > amp/filter; power supply; coil) and have them work the first time! Mighty
> > good work you do.
> >
> > The unknown, of course, will be how it responds in a classroom building,
> > with student activity, and major streets a hundred yards away on two sides.
> > But after an initial period of "pegging" - and after adding a large
> > compression factor - the trace flattened out and gave a nice little "quake"
> > with a carefully calibrated foot stomp :-)
> >
> > Hopefully, will be completing Ridgeway High School's system within the next
> > few days.
> >
> > School is ending - we won't really get to see student monitoring until the fall.
> > And Biology prof, Toni Brautigan, who has provided wonderful support during
> > the long assembly process, is moving to Arizona :-(
> >
> > I wonder if you - or Steve Hammond - or Ken may have assembled documentation
> > which could form a core handbook/manual for St. Agnes and Ridgeway High Schools?
> >
> > Thanks for your help! And thanks, also, to Edward Cranswick for launching
> > us, and Steve Hammond, for building our foundation.
> >
> >
> >
> >
> >
> >
> > Charlie Rond -\/\--Public Seismic Network-Memphis
> > rond@................ (901) 360-0302 [ free BBS ]
> > http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
> >
> >
> > _____________________________________________________________________
> >
> > Public Seismic Network Mailing List (PSN-L)
> >
> > To leave this list email listserver@............. with the body of the
> > message: leave PSN-L
> >
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: St. Agnes High School seismo works!
Date: Fri, 6 Jun 1997 14:00:24 -0400
Charlie,
Two atta boys on your high school installations. Is this associated wi=
th
PEPP? A few other questions:how many axes, what seismometers, where
installed (basement?) , running SDR, etc.?
Keep us posted on how it all works.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: quake???
Date: Fri, 6 Jun 1997 14:00:15 -0400
Clark,
Glad to know about another station in the great seismic wasteland! I g=
ot
a good quake here in NJ but the first stuff above bg was at 6/5 21:56:00.=
=
It looked abnormal--no big peak (surface waves) and it went on and on at
relatively constant amplitude as if it were a deep 'quake. My sig/noise
ratio was 32. I could still see it above bg for > 4.5 hrs.!
I'll check with Bill Skolnic in Oakland, NJ to see if he got it.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Rond <rond@................>
Subject: Re: St. Agnes High School seismo works!
Date: Fri, 06 Jun 1997 14:17:21 -0500
Bob,
> Two atta boys on your high school installations.
Thanks, I can always use 'em!
> Is this associated with PEPP?
No, strictly PSN.
>A few other questions:how many axes, what seismometers, where
>installed (basement?) , running SDR, etc.?
Only one axis each. Using home-built Lehman's. Teacher-husband built at
Ridgeway and Rond-built at St. Agnes. St. Agnes is installed on concrete
slab in a nifty spot-under a closed cabinet in a classroom-anteroom.
Ridgeway's, so far, is on 2nd floor in classroom-anteroom. St. Agnes
running SDR, Ridgeway running EMON.
Charlie Rond -\/\--Public Seismic Network-Memphis
rond@................ (901) 360-0302 [ free BBS ]
http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Rond <rond@................>
Subject: Re: St. Agnes High School seismo works!
Date: Fri, 06 Jun 1997 14:23:11 -0500
Steve,
>Way to go, Charlie. That's great. I still have some old hardware; old XT
>and AT class stuff, a few mono, color, and EGA displays, a couple of dot
>printers, and a few 2400 baud modems sitting around. Need anything before
>I give it away?
Really need an XT hard drive. Ridgeway needs a color monitor and color
card, and could use a 2400 baud modem. Let me know what the shipping would
cost.
Thanks again for all your help! We could not have done it without you.
Charlie Rond -\/\--Public Seismic Network-Memphis
rond@................ (901) 360-0302 [ free BBS ]
http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: St. Agnes High School seismo works!
Date: Fri, 06 Jun 1997 13:48:36 -0600
Charlie-
I am very impressed that you have got all the instrumentation installed
and working in the school, but ultimately the most important element of
the PSN is the "Public". Connecting the kids to the Earth via the
school and the PSN is your big achievement!
-Edward
Charlie Rond wrote:
>
> Larry,
>
> Got everything hooked up today at St. Agnes High School and it all works!
>
> It's an amazing experience to hook up your electronics (A/D card;
> amp/filter; power supply; coil) and have them work the first time! Mighty
> good work you do.
>
> The unknown, of course, will be how it responds in a classroom building,
> with student activity, and major streets a hundred yards away on two sides.
> But after an initial period of "pegging" - and after adding a large
> compression factor - the trace flattened out and gave a nice little "quake"
> with a carefully calibrated foot stomp :-)
>
> Hopefully, will be completing Ridgeway High School's system within the next
> few days.
>
> School is ending - we won't really get to see student monitoring until the fall.
> And Biology prof, Toni Brautigan, who has provided wonderful support during
> the long assembly process, is moving to Arizona :-(
>
> I wonder if you - or Steve Hammond - or Ken may have assembled documentation
> which could form a core handbook/manual for St. Agnes and Ridgeway High Schools?
>
> Thanks for your help! And thanks, also, to Edward Cranswick for launching
> us, and Steve Hammond, for building our foundation.
>
> Charlie Rond -\/\--Public Seismic Network-Memphis
> rond@................ (901) 360-0302 [ free BBS ]
> http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Rond <rond@................>
Subject: Re: St. Agnes High School seismo works!
Date: Fri, 06 Jun 1997 14:57:19 -0500
Edward,
> Congratulations! The best thing that I could send you would be an
>earthquake, but I haven't worked out how to do that yet.
>-Edward
>
>PS. Ted Blank deserves a great deal of credit for the PSN because if he
>hadn't put together the software to turn a PC into a waveform
>acquisition device, we'd never have gotten off the ground. I realized
>the other day that I have been remiss in not referring to his critical
>contribution.
Thanks for the congrats...and especially, thanks for the reminder about Ted
Blank. I realized the same thing after I signed off my earlier message.
We are always inclined to think about the hardware and take the software for
granted.
TED BLANK is the author of the software which replaced our stumbling
attempts, let us take off and all begin to fly in formation. It was surely
the single most important element in the creation of the PSN and the
coordinated amateur seismology effort world-wide.
He also is the principle in the story I love to tell to illustrate the
"miracle" of the Internet. Ted sent E-mail from Tokyo asking about any
suggestions for his latest EMON update. Within a couple of hours, he had
incorporated my suggestions, FTP'd the new version to California, I'd FTP'd
it, downloaded it, and had it installed, tested and operating on my system
in Memphis!
And while we thank those deserving, special thanks go to TED SMITH for the
GeoInfo Network which kept us linked together and communicating before we
were spun up into the World Wide Web. And to Pete Rowe for his Amp design.
Dorothy Darby also earned her wings over several years, administrating the
PSN network, taking care of us all (not to mention husband, Jerry) and
relaying so that our nodes were current, etc....all the while with a radio
mike in one hand talking to the Ham net in Pasadena.
Whatever we accomplish has been on the shoulders of a number of stalwarts.
Charlie Rond -\/\--Public Seismic Network-Memphis
rond@................ (901) 360-0302 [ free BBS ]
http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ct@....... (Charlie Thompson)
Subject: URL Problem w/USGS
Date: Fri, 06 Jun 1997 15:16:34 -0500
Out of nowhere the following URL doesn't work from my ISP:
http://wwwneic.cr.usgs.gov/neis/finger/quake
Can anyone else get this link to work? I'm always suspicious of
my ISP's DNS.
Thanks in advance,
Charlie Thompson
-------------------------------------------------------------------------
Charlie Thompson
WB4HVD 30.112N 97.891W
800 Elliott Ranch Rd.
Buda, TX 78610
http://www.onr.com/user/ct/ct.html
Seismic Station .BUE
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: URL Problem w/USGS
Date: Fri, 06 Jun 1997 12:20:54 -0700
Also not working here... and I run my own DNS.
-Larry
At 03:16 PM 6/6/97 -0500, you wrote:
>Out of nowhere the following URL doesn't work from my ISP:
>
> http://wwwneic.cr.usgs.gov/neis/finger/quake
>
>
>Can anyone else get this link to work? I'm always suspicious of
>my ISP's DNS.
>
>Thanks in advance,
>
>Charlie Thompson
>
>
>
>
>
>-------------------------------------------------------------------------
>Charlie Thompson
>WB4HVD 30.112N 97.891W
>800 Elliott Ranch Rd.
>Buda, TX 78610
>http://www.onr.com/user/ct/ct.html
>Seismic Station .BUE
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: URL Problem w/USGS
Date: Fri, 06 Jun 1997 14:25:53 -0600
Charlie-
I just tested it, and it just worked for me, but I'm local, i.e., in
the building.
-Edward
Charlie Thompson wrote:
>
> Out of nowhere the following URL doesn't work from my ISP:
>
> http://wwwneic.cr.usgs.gov/neis/finger/quake
>
> Can anyone else get this link to work? I'm always suspicious of
> my ISP's DNS.
>
> Thanks in advance,
>
> Charlie Thompson
>
> -------------------------------------------------------------------------
> Charlie Thompson
> WB4HVD 30.112N 97.891W
> 800 Elliott Ranch Rd.
> Buda, TX 78610
> http://www.onr.com/user/ct/ct.html
> Seismic Station .BUE
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Ray Gallagher <rayban1@.............>
Subject: Re: URL Problem w/USGS
Date: Fri, 06 Jun 1997 13:29:16 -0700
Charlie,
I just tried it and it worked for me, but maybe it was down when you
tried? You can also use this for the same info...
http://quake.wr.usgs.gov/cgi-bin/finger?quake@.................
Take care & stay safe! Ray
Charlie Thompson wrote:
> Out of nowhere the following URL doesn't work from my ISP:
>
> http://wwwneic.cr.usgs.gov/neis/finger/quake
>
> Can anyone else get this link to work? I'm always suspicious of
> my ISP's DNS.
>
> Thanks in advance,
>
> Charlie Thompson
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Joan Chesleigh-Blaine <jcblaine@...........>
Subject: Re: URL Problem w/USGS
Date: Fri, 06 Jun 1997 13:31:28 -0700
Try this.... it's working. Incidentally, your link did not work for me
either.
http://quake.wr.usgs.gov/cgi-bin/finger?quake@.................
Joan Blaine
Charlie Thompson wrote:
> Out of nowhere the following URL doesn't work from my ISP:
>
> http://wwwneic.cr.usgs.gov/neis/finger/quake
>
> Can anyone else get this link to work? I'm always suspicious of
> my ISP's DNS.
>
> Thanks in advance,
>
> Charlie Thompson
>
> ----------------
> --------------------------------------------------------
> Charlie Thompson
> WB4HVD 30.112N 97.891W
> 800 Elliott Ranch Rd.
> Buda, TX 78610
> http://www.onr.com/user/ct/ct.html
> Seismic Station .BUE
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
>
> message: leave PSN-L
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Rond <rond@................>
Subject: Re: URL Problem w/USGS
Date: Fri, 06 Jun 1997 16:27:37 -0500
Charlie,
>Charlie-
> I just tested it, and it just worked for me, but I'm local, i.e., in
>the building.
>-Edward
>
>Charlie Thompson wrote:
>>
>> Out of nowhere the following URL doesn't work from my ISP:
>>
>> http://wwwneic.cr.usgs.gov/neis/finger/quake
>>
>> Can anyone else get this link to work? I'm always suspicious of
>> my ISP's DNS.
It does NOT work from here.
Charlie Rond -\/\--Public Seismic Network-Memphis
rond@................ (901) 360-0302 [ free BBS ]
http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Rond <rond@................>
Subject: Re: St. Agnes High School seismo works!
Date: Fri, 06 Jun 1997 16:43:54 -0500
Edward,
> I am very impressed that you have got all the instrumentation installed
>and working in the school, but ultimately the most important element of
>the PSN is the "Public". Connecting the kids to the Earth via the
>school and the PSN is your big achievement!
Thanks very much. Come back and see us. We need another shot at converting
you from veggie to Memphis barbecue :-)
Charlie Rond -\/\--Public Seismic Network-Memphis
rond@................ (901) 360-0302 [ free BBS ]
http://gandlf.ceri.memphis.edu/~rond http://gandlf.ceri.memphis.edu/~rond/psn
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Ron Westfall <westfall@...............>
Subject: Re: URL Problem w/USGS
Date: Fri, 06 Jun 1997 17:25:54 -0700
That URL does not work for me either, however after some experimenting
I found the following URL works:
http://gldss7.cr.usgs.gov/neis/finger/quake
I don't remember whether
http://wwwneic.cr.usgs.gov/
had anything interesting, but
http://gldss7.cr.usgs.gov/
sure does.
Ron Westfall
Charlie Thompson wrote:
>
> Out of nowhere the following URL doesn't work from my ISP:
>
> http://wwwneic.cr.usgs.gov/neis/finger/quake
>
> Can anyone else get this link to work? I'm always suspicious of
> my ISP's DNS.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: URL Problem w/USGS
Date: Fri, 06 Jun 1997 17:19:15 -0700
Larry Cochrane wrote:
>
> Also not working here... and I run my own DNS.
> -Larry
>
> At 03:16 PM 6/6/97 -0500, you wrote:
> >Out of nowhere the following URL doesn't work from my ISP:
> >
> > http://wwwneic.cr.usgs.gov/neis/finger/quake
> >
> >
> >Can anyone else get this link to work? I'm always suspicious of
> >my ISP's DNS.
> >
> >Thanks in advance,
> >
> >Charlie Thompson
> >
> >
> >
> >
> >
> >-------------------------------------------------------------------------
> >Charlie Thompson
> >WB4HVD 30.112N 97.891W
> >800 Elliott Ranch Rd.
> >Buda, TX 78610
> >http://www.onr.com/user/ct/ct.html
> >Seismic Station .BUE
> >
> >
> >_____________________________________________________________________
> >
> >Public Seismic Network Mailing List (PSN-L)
> >
> >To leave this list email listserver@............. with the body of the
> >message: leave PSN-L
> >
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
Hi Larry
Doesn't work here either. That was the problem I mentioned to you last
week.
Barry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Plyler <cplyler@.............>
Subject: Re: quake???
Date: Fri, 06 Jun 1997 21:19:45 -0400
At 14:00 6/6/97 -0400, you wrote:
>Clark,
> Glad to know about another station in the great seismic wasteland! I got
>a good quake here in NJ but the first stuff above bg was at 6/5 21:56:00.
>It looked abnormal--no big peak (surface waves) and it went on and on at
>relatively constant amplitude as if it were a deep 'quake. My sig/noise
>ratio was 32. I could still see it above bg for > 4.5 hrs.!
> I'll check with Bill Skolnic in Oakland, NJ to see if he got it.
>Bob Barns
I received it using direct electrical detection equipment in
North Carolina. Very long period. Also am very curious as to origin.
Charlie
Elfrad Group
35.728N
80.810W
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ACole65464@.......
Subject: Re: Noise Levels
Date: Fri, 6 Jun 1997 22:30:40 -0400 (EDT)
Hello PSN,
Thank you to those who responded to my question concerning seismometer site
acceleration levels. After posting to the PSN I was having second thoughts
about how I calculated the acceleration levels at my seismometer site.
Feed-back from several of you provided me with enough incentive to go back
and recalculate it all again. I found that I had made a MISTAKE. I was a
little hasty doing the calcs the first time around. I am glad to have a peer
group like the PSN to pick up my errors. These are the recalculated numbers
for my site's accelerations:
1.5 microns P-P on a quiet day.
7 microns P-P on very windy day (I have fences near the seismometer
pit).
15 microns P-P when trains roll by a mile away (first class noisy site).
Where I live on Puget Sound there is something like 800 - 2000 feet of
glacial till under foot, so I expect to see slightly higher accelerations
(Jello effect) than if I had the seismometer installed on solid bedrock.
Thanks for the feed-back guys, it helped me to better understand what I was
doing wrong and now I know something about your sites.
Bye for now,
Allan Coleman, Seattle
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: when replying to e-mail messages
Date: Sat, 07 Jun 1997 15:48:11 +1200
hi guys,
please remember when you are replying to e-mail messages If
you are going to leave the comments of the previous sender in you reply
ADD your comments to the top where they are easily read instead of having
to scroll down through heaps of stuff trying to find your reply
most are ok It may be some of the newcomers to the net thatthe teaching
is aimed at..
Cheers Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: seismo history
Date: Sat, 07 Jun 1997 15:57:03 +1200
Hi all
I got this e-mail and wonder if anyone can suggest some read
ing references to the person concerned......
TNX Dave
From: Nicholas Dugbartey <nicholas@...........>
Subject: SEISMOMETERS
Hi Dave,
I was looking for information on seismometers, and I am hoping
you will be able to provide me with information, or direct me to some
reliable sources.
I am interested in finding out about the evolution of the seismometer: how
it has changed from the ancient Chinese seismometer to the current ones
being used.
If u also have material that you can send by fax, my fax number is
(408) 279-7197
Thank you for your time and assistance,
Nicholas Dugbartey
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: URL Problem w/USGS
Date: Sat, 07 Jun 1997 08:16:04 -0700
Ron Westfall wrote:
>
> That URL does not work for me either, however after some experimenting
> I found the following URL works:
>
> http://gldss7.cr.usgs.gov/neis/finger/quake
>
> I don't remember whether
>
> http://wwwneic.cr.usgs.gov/
>
> had anything interesting, but
>
> http://gldss7.cr.usgs.gov/
>
> sure does.
>
> Ron Westfall
>
Ron,
I have never come across the "gldss7" server before.
Where is it and what is it used for?
Seems to duplicate the wwwneic server.
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
mailto:watson@................
http://www.seismo-watch.com
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Snowballs from space
Date: Sat, 07 Jun 1997 12:13:44 -0700
Hi Dave and PSN'ers
Interesting stuff Dave, thanks for the post. Do you (or anyone else) know
how many seismic stations we had going at the peek of your moon exploration?
-Larry Cochrane
Redwood City, PSN
At 11:51 AM 6/6/97 +1200, Dave Nelson wrote:
>Lloyd
>
> the seismometers that were placed and operating on the moon
>between Nov. 1969 qnd Sept. 1977, detected moonquakes attributed to 3
>causes. Impacts, Shallow ... 0-60km depth, and deep 600-900 km depth.
> the deep ones seemed to come from a limited number of foci ~50 that are
>on the infered mantle - core boundary. The seismograms of different
>events from the same foci are almost identical with each other and each foci
>becomes active at some definite time each month. This tidal forces are the
>cause. There are peaks of activity 14 days apart and secondary peaks at 206
>day intervals which would coincide with the Sun's contribution to the tidal
>forces.
>
> the shallow events are thought to result from the release of crustal
>stresses. Only about a dozen of these events were recorded and no obvious
>patterns were seen.
>
> Moonquake seismograms are quite different from terresterial ones. The
>movements are much higher in freq., and reveberation continues for a very
>long time .... for the shallow and deep events up to 50 minutes and for
>impacts... well in excess of an hour for the larger ones.
>It was hard to pick phases and there were no clear surface waves, the very
>dry lunar surface is thought to be responsible.
>
> The crust was found to have an avg. P - velocity of ~6.7km/s and the
>mantle has a fairly uniform p vel. of ~ 8 km/s
>
>Who knows whether the impacts on the moon that were recorded were solid or
>icy objects!!!
>
>BTW a seismograph was landed on Mars in Nov. 1976 on the Plains of Utopia,
>by the Viking spacecraft and only one undisputable event was recorded in the
>546 days of operation and it was an event of about M6.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Noise Levels
Date: Sat, 07 Jun 1997 16:25:43 -0600
Allan-
I still do not understand how to interpret microns, 10**-6 m, i.e., a
measure of displacement, in terms of acceleration, i.e., m/s**2 or
displacement per second squared.
Where are you located on the Puget Sound? I don't see you on the PSN
map.
-Edward
ACole65464@....... wrote:
>
> Hello PSN,
> Thank you to those who responded to my question concerning seismometer site
> acceleration levels. After posting to the PSN I was having second thoughts
> about how I calculated the acceleration levels at my seismometer site.
> Feed-back from several of you provided me with enough incentive to go back
> and recalculate it all again. I found that I had made a MISTAKE. I was a
> little hasty doing the calcs the first time around. I am glad to have a peer
> group like the PSN to pick up my errors. These are the recalculated numbers
> for my site's accelerations:
> 1.5 microns P-P on a quiet day.
> 7 microns P-P on very windy day (I have fences near the seismometer
> pit).
> 15 microns P-P when trains roll by a mile away (first class noisy site).
> Where I live on Puget Sound there is something like 800 - 2000 feet of
> glacial till under foot, so I expect to see slightly higher accelerations
> (Jello effect) than if I had the seismometer installed on solid bedrock.
> Thanks for the feed-back guys, it helped me to better understand what I was
> doing wrong and now I know something about your sites.
> Bye for now,
> Allan Coleman, Seattle
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Seismo's on moon
Date: Sun, 08 Jun 1997 13:56:41 +1200
Hi all,
The rough map I have access to shows that there were 5
seismometers sited ( Ah... but the text says 6 units were operated for
varing lengths of time. The number of events recorded by each station
per year varied between 600 - 2000 depending on the site. A major portion
of these were very small and total energy released over a year was barely
sufficient to produce a M2 quake.
The text goes on to say that these numbers did not include the very small
thermally induced events that accompanied abrupt temp change at lunar
sunrise and sunset. It is thought that these events resulted from small
scale cracking and slumping of the surface.
Dave
( all comments from "Earthquakes " by G. A. Eiby the retired
superintendant of the Seismological Obs. in Wellington, NZ. )
At 12:13 PM 6/7/97 -0700, you wrote:
>Hi Dave and PSN'ers
>Interesting stuff Dave, thanks for the post. Do you (or anyone else) know
>how many seismic stations we had going at the peek of your moon exploration?
>-Larry Cochrane
>Redwood City, PSN
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "John Hernlund" <69277@..................>
Subject: moon thermal expansion
Date: Sat, 7 Jun 1997 21:07:20 -0700 (MST)
> The text goes on to say that these numbers did not include the very small
> thermally induced events that accompanied abrupt temp change at lunar
> sunrise and sunset. It is thought that these events resulted from small
> scale cracking and slumping of the surface.
This is an interesting thought. Does anyone know:
- What is the net change in temperature on the surface of the moon
throughout a lunar day?
John Hernlund
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Nthrn Calif. event
Date: Sun, 08 Jun 1997 16:10:00 +1200
Phil and Barry,
putting your seismograms above one another in
winquake and it is amazing how similar they look even some of the peaka
in the "P" waves coincide. also both seismograms showed the long train of
LP waves have seen that a few times now on Calif. events.... first noticed
on one of Larry's records of some 6 mths to a year ago.
Phil I noticed that you added the info presum. from the USGS to your one
and it was around a M2.2 Barry's mag corr. factor was extremely high
giving the quakle a M5.5 he may have to lower it somewhat to give more
realistic readings of events,
and Phil your mag corr. factor not so far out.
I find on my sys. that the mag corr. has to be altered depending on
whether it is a regional or distant event
It was good to see that your origin times were within a second or two of
each other
Keep up the good work
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Al Allworth <aallworth@........>
Subject: Move to Oregon
Date: Sat, 7 Jun 1997 21:41:42 -0700
Hello to all from Oregon,
Well, the worst is over. Everything except my pickup is now in Oregon. Will
be getting a seismometer connected soon. I can expect a lot of wave noise,
and am anxious to see how bad it will be. I think it should be in the higher
frequencies and should be filterable. Has anyone operated a seismograph 1/2
mile from the beach? What am I in for?
____________________________________________________________________________
Al Allworth, Gold Beach, OR aallworth@........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Nthrn Calif. event
Date: Sat, 07 Jun 1997 21:07:35 -0700
Hi Gang,
This event has not been reported yet by the USGS, or any other agency, and
it happened over 9 hours ago! I believe it to be an event up north, maybe
around Fort Bragg or Cape Mendocino. These events are usually out in the
ocean, just off of the coast. I get a magnitude of around ML5.0 and a
distance of ~400km.
> Phil I noticed that you added the info presum. from the USGS to your one
>and it was around a M2.2 Barry's mag corr. factor was extremely high
>giving the quakle a M5.5 he may have to lower it somewhat to give more
>realistic readings of events,
> and Phil your mag corr. factor not so far out.
This can't be a 2.2ML, one would not get a 2.2 over 300km away. Also the
arrival of the P wave on the USGS sensors I monitor place the event up
north, not down south.
For those of you who monitor the ca.earthquakes news group you may have
seen a prediction made by one of the list members, Bob Shannon. Below is
his prediction:
EARTHQUAKE WARNING!
June 6, 1997
15:00 hours PCT
A tremendous build-up of internal mental pressure! This goes beyond
classic into the probability realm.....Therefore..after my wife
mentioned this looks like quake mentality, I am issuing the following
warning:
A quake ranging from moderate to severe (>4.8 yet maybe as high as
7.0+). Because the symptoms are so severe, I am figuring that the
further away from me (Spokane), the larger the quake. This is normally
the case however due to the severity of the symptoms, the ratio will
be higher.
Because I still hold the magnetite hypothesis to be very likely, I
will use an arbitrary but central Northern California point as the
radius...I am thinking here as I write, that although Fort Bragg on
the Mendocino Coast is not prone to direct quakes, it is in between
the area of highest likelihood and the second-most such. Therefore
Fort Bragg, CA will be the radius center.
Due to the type of symptoms, the time frame will be longer than
usual. I am looking at 2 weeks here for a M>5 within 350 miles. Also I
am using the alto-concentric circles, which is a self cancelling,
Schroedingers Cat type of wave hypothesis. Unfortunately we cannot use
a priori in this case:<
The location of the second radius of alto-concentric circles is
Portland Oregon.
Our series of 3 warnings (this being #4) is 0 for 3, as opposed our
onging hits at 75-78%, but considering the lack of movement in N Cal
and within radius, I think we are closer to target this time.
Date as above
Bob Shannon
Pinpoint News
--------------------------------------------------------------------------
Well, if the event is near Fort Bragg then it looks like Bob has a hit...
Hopefully we will have some numbers soon.
PLEASE lets not get into any long discussion on EQ prediction, I don't
think this is the place for that. I included, some what reluctantly, the
above info as a point of interest only and because Bob is a member of the
list.
Bob, do you think this is the event you where "feeling"?
Regards,
Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Nthrn Calif. event
Date: Sat, 07 Jun 1997 21:55:41 -0700
Hi Dave
I have noticed there is a coorelation between the magnitude and the
measuring of long period waves;or maybe it's just measuring a larger
event from a distance ( m=4+ ). I maybe a little high but at that
distance I would still say over 4. BTW I was also amazed by the
similarity between our two records. If I knew how to read my first
arrival it should be possible to tell whether it came from north or
south.
Barry
David A Nelson wrote:
>
> Phil and Barry,
> putting your seismograms above one another in
> winquake and it is amazing how similar they look even some of the peaka
> in the "P" waves coincide. also both seismograms showed the long train of
> LP waves have seen that a few times now on Calif. events.... first noticed
> on one of Larry's records of some 6 mths to a year ago.
>
> Phil I noticed that you added the info presum. from the USGS to your one
> and it was around a M2.2 Barry's mag corr. factor was extremely high
> giving the quakle a M5.5 he may have to lower it somewhat to give more
> realistic readings of events,
> and Phil your mag corr. factor not so far out.
>
> I find on my sys. that the mag corr. has to be altered depending on
> whether it is a regional or distant event
>
> It was good to see that your origin times were within a second or two of
> each other
>
> Keep up the good work
>
> Dave
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Nthrn Calif. event
Date: Sun, 08 Jun 1997 18:54:11 +1200
Ok Barry,
wonder where Phil got his M2.2 report from ??? maybe
your reading is closer to the truth, Phil's reading off winquake was ~M4.7
not far from yours ??? I may owe you a humble apology.
Larry yes I agree the chances of recording a M2.2 at 400 km + also
went through my mind as being a wee bit far fetched. I can just record a
M3.5 at about 320 km maximum or the same as the distance between Dunedin
and Christchurch.
Dave
At 09:55 PM 6/7/97 -0700, you wrote:
>Hi Dave
> I have noticed there is a coorelation between the magnitude and the
>measuring of long period waves;or maybe it's just measuring a larger
>event from a distance ( m=4+ ). I maybe a little high but at that
>distance I would still say over 4. BTW I was also amazed by the
>similarity between our two records. If I knew how to read my first
>arrival it should be possible to tell whether it came from north or
>south.
> Barry
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: George Bush <gbush@.......>
Subject: Re: Move to Oregon
Date: Sat, 07 Jun 1997 23:45:23 -0700
Al-
At 09:41 PM 6/7/97 -0700, you wrote:
>Hello to all from Oregon,
>Well, the worst is over. Everything except my pickup is now in Oregon. Will
>be getting a seismometer connected soon. I can expect a lot of wave noise,
>and am anxious to see how bad it will be. I think it should be in the higher
>frequencies and should be filterable. Has anyone operated a seismograph 1/2
>mile from the beach? What am I in for?
I live about a block from the ocean at Sea Ranch CA. I am just starting
out and so can not quantify the noise, but I can easily receive any M7
quake from anywhere in the world, M6 quakes from Mexico, M4 from Punta
Gorda CA, and M3 from the Geisers (about 30 mi away). I see quiet times
when I could probably set my dead band threshold much smaller, but when the
winter storms are pounding on our cliffs, it is impossible to see anything
else. I also see daily noise that correlates with the wind picking up, but
I do not know if this is primarily caused by the wind flexing the garage
and mounting slab, or secondarily by the wind whipping up the waves.
So all-in-all I am very pleased with what and when I can monitor seismic
events from near the beach and think that you probably will do very well.
George
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Numbers for the northern cal quake
Date: Sun, 08 Jun 1997 03:09:40 -0700
Hi,
The quake finger server at dmc.iris.washington.edu has the following for the
event that happened yesterday.
DATE-TIME SEC LAT LON DEPTH MAG REGION NUMBER VBB LP
9706071940 00. 40.41 N 126.23 W 10 4.8 OFF COAST OF NORTHERN CALI 15 07
-Larry Cochrane
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: moon seismology
Date: Mon, 09 Jun 1997 00:26:35 +1200
OK you lot,
I have spent a couple of hours tonite adding a subpage
off my quake page to give some info on Lunar seismology. there are images
of ~45 kB each
1) face of moon showing seismo sites
2) crossection of the moon
3) seismograms of different types of events
I will keep this page active unless some one cries murder over copywrite
infringement etc.
I have ackn. the source and so take no credit myself !!!!
PS. thanks Larry for the data on the Nthrn Calif. event M4.8 that puts
Phil's Winquake estimate smack on.
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Quant. Seismic noise
Date: Sun, 8 Jun 1997 09:55:06 -0400
Allan Coleman,
Re:your letter about seismic noise levels. Good for you! I think that=
we all would learn faster if more effort was spent on being more
quantitative. =
I measure and record my noise daily by simply hitting the C key in SDR.=
=
This resets the max and min display. I record the max and min after 1 mi=
n.
This gives a measure proportional to the p-p noise (over 1 min.) and the=
se
are converted to velocities using the calibration by the meter-movement
calibrator (like you used). The numbers below are for a 16 to 30 sec (I
change it from time to time) horizontal Lehman with nearly critical dampi=
ng
and a 6-pole low-pass filter which is 3db down at 0.08Hz.
For 40 daily readings between Mar 12 and Apr 12 '97, I got a median
velocity of 771 nm/sec (nanometers/sec), a mean of 914 nm/sec. A
probability plot showed that the distribution is highly skewed with low
values predominating. The avg. of the lowest 10 (of the 40) was 394 nm/s=
ec
and the highest was 2560. The highest was 6.7 times the avg. of the 10
lowest.
Your revised numbers, 1.5 microns for quiet and 7 microns for windy sti=
ll
look peculiar--are these <really> dispalcements or do you mean velocities=
(microns/sec)? If these are velocities they would be 1500 nm/sec and 7,0=
00
nm/sec. and are higher than my values but not unreasonable. Cunningham
reported 500 nm/sec p-p for quiet and 2,000 nm/sec p-p for noisy which is=
very comparable to my figures. =
I find a fairly good correlation with wind velocity--wind makes the tre=
es
sway and we have a lot of trees. This even though the only wind data I
have is the peak vel. over each 24 hr. period. Also, I'm only 30 miles
from the Atlantic ocean and the books say that wave action creates a lot =
of
long period noise.
Aki & Richards, 'Quantitative Seismology', 1980, vol. 1, p 497...
discusses ambient seismic noise esp. Fig. 10.11. This fig. shows 2
curves--noisy and quiet locations. These curves are for a "station on ha=
rd
basement rock remote from cultural activities when there is no strong
wind." Both curves show a fairly sharp peak at 0.15Hz(7 sec.) (I often
see this in the FFT of my 'grams in spite of the low-pass filter. The pe=
ak
is much suppressed when my free period is 30 secs. compared to 16 secs). =
There is a minimum in the curves of Fig. 10.11at about 0.013Hz (77 sec.).=
=
Getting numbers from Fig. 10.11 is uncertain since the plot is small an=
d
the values are varying rapidly in the range of interest. I think that I
understand how to convert these numbers to nm/sec but I'm not sure. For
what it's worth, at 0.06 Hz (appropriate for a 16 sec. pendulum period) I=
get:
Power spectral density velocity
Noisy 8e-10(cm/sec)^2/Hz 5000 nm/sec
Quiet 1e-12 2 =
A range of 2 to 5000 is wide enough to fit almost anyone, I suppose. =
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: History
Date: Sun, 8 Jun 1997 09:55:13 -0400
Nicholas Dugbartey & Dave Nelson,
There is a good history in "Earthquakes and Geological Discovery" by
Bruce Bolt, W. H. Freeman & Co. , 1993. This is in print.
This book is a really magnificent introduction to seismology! It was
written by a master of both the subject matter and clear exposition. The=
photos and figures are very well done. It gives both general information=
and information at a deeper technical level. You can get it from your
local library on inter-library loan, but I'll bet you will want to buy it=
after the first glance.
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Re: quake???
Date: Sun, 8 Jun 1997 09:55:16 -0400
Charlie Plyler,
You have me stumped--what is 'direct electrical detection equipment'?
Bob Barns
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Charlie Plyler <cplyler@.............>
Subject: Re: quake???
Date: Sun, 08 Jun 1997 10:56:49 -0400
Bob Barns and All,
For the past several years I have been experimenting with the
possibilities of global ULF and ELF signal detection through the
earth. Along with using seismic detection devices we directly
interface with the earth and measure electrical transients between
probes.
Larry's A/D card along with the Winquake program are very useful
when used with suitable low pass filters. Using this method the
propagation factor is quite different and much faster. Near real
time. One draw back however is determining quickly the distance,
magnitude, and depth. Currently we are working on that problem
by linking widely separated sites.
Later,
Charlie
>Charlie Plyler,
> You have me stumped--what is 'direct electrical detection equipment'?
>Bob Barns
>
Elfrad Group
35.728N
80.810W
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Rev. Bob Shannon" <rshannon@.......>
Subject: Re: Nthrn Calif. event
Date: Sun, 8 Jun 1997 08:21:50 -0700 (PDT)
On Sat, 7 Jun 1997, Larry Cochrane wrote:
>
> Bob, do you think this is the event you where "feeling"?
>
Depending on the concensus it may be. I understand that Q's which are far
out in the water are less likely to be measured 'correctly'. Until a
better location and M come in, I think I'll hold out. I also must contact
friends in Fort Bragg, Mendo and Petrolia to inquire if any felt this
event....I did recieve a message from Olga at the Geysers with some
corroborating data on my 'feelings'.
I must add that the PSN is a very handy group. When Q's are in locations
without good local instrumentation, you folks seem to have a good handle
on the situation. Thanks for asking.
Bob
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.......>
Subject: Re: Quant. Seismic noise
Date: Sun, 08 Jun 1997 21:25:39 -0700
Bob --
I appreciate your comments on quantifying seismic noise.
I find that using an RMS measurement with a fairly long integration period
(I've been using 30 min) for noise gives pretty repeatable numbers and
filters out almost all cultural noise. It does respond, however, to
teleseismic events.
The RMS noise measurements at my location range from about 50nm/s (quiet)
to about 250nm/s (noisy).
On a related subject, I've been using the ratio of peak-to-peak to RMS
(30min) as an alarm for regional events. The purpose of an alarm is to
detect events, or conversely to not trigger unless there is an event. The
ratio predicts an expected peak-to-peak level of background noise, and is
based on something (the RMS value) that is pretty closely related to the
background noise level. Anything above this ratio is predicted to be other
than background noise (possible event), regardless of what the background
noise level actually is. A ratio threshold of around 10:1 seems to work
well, for a wide range of background noise levels. In order to catch
surface waves of teleseismic events, I also save data if the RMS value is
above a certain threshold. I'd appreciate any comments on this subject too.
Karl Cunningham
La Mesa, CA.
karlc@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: bfryer@............ (Bob Fryer)
Subject: Re: quake???
Date: Mon, 9 Jun 1997 02:32:52 -0700 (PDT)
Hello gang,
I returned recently from the New Energy conference in Denver. This is one
of many interesting items that I picked up.
"E.L.F. Magnetometer for Eathquake Prediction and Nuclear Test Monitoring,"
Proposal to SBIR US DOD, US Air Force Topic No. 245 1989, by Thomas Valone,
P.E., of Integrity Research Institute ( Note: Small Business Inovation
Research)
Before I first met him in 1983 at a USPA conference, Tom Valone had already
been involved in practical applications for the newly emerging views on
physics. At USPA conferences, Valone has had access to Jerry Gallimore,
Tom Beardon (Richard Hoagland's hyperdimensional physics), Dr. Andrija
Puharich, Dr. Elisabeth Rauscher and Bill Bise, and many others. I should
not have been surprised to find this proposal, dated 1989.
One of my contacts, on the San Andreas, has been recording some interesting
magnetic and resistance pre-quake anomalies for more than a year. I will
be visiting her on the 21 & 22 +, then at the Dowser's Conference in Santa
Cruz, from the 27th to 7/1. Will have to head home soon after that, so I
can get ready for USPA in Indiana, July 18-21. Will putter around SoCal
June 24-26, seeing the sights and looking for a place to hang my hat.
Take care,
Bob
It contains some interesting statements:
"....it was found as early as 1799 (!) and 1822 that the magnetic dip
needle could be altered by as much as 48 minutes at a distance of hundreds
of miles from an earthquake.... (includes quote from Von Hoff, 1822)"
"_Seismomagnetometry_
.....several leading researchers sought to take advantage of the plate
stress-induced rock magnetization which decreases in the direction of the
applied compression and increases at right angles to the stress (Breiner
and Kovach, 1968) (Ohnaka & Kinoshita, 1968)...."
"....the creation of ELF waves by the piezomagnetic and tectonomagnetic
effects has all but been ignored in the literature...." Note that this was
before Loma Prieta where Fraser-Smith "discovered" the signals.
"What has not been well documented is the observation that from three to
ten days in advance of an earthquake, each tectonic plate movement produces
characteristic ELF frequency signatures. The plate movement is thus
coupled to the Schumann cavity... There are also indications that longer
lead times are associated with stronger seismic events (Byrd, 1988)."
[This, and the language of other statements, suggests that there are
pre-earthquake tectonic movements. This is in keeping with the views of
Adam Trombly who, with David Farnsworth, apparently predicted the March
1993 Oregon quake. Valone and Trombly had much contact.]
"this method can greatly exceed the current U.S. Geolgical Survey estimated
20 to 30% accuracy in earthquake prediction (Johnston (b), 1988)."
------------------------
>Bob Barns and All,
>For the past several years I have been experimenting with the
>possibilities of global ULF and ELF signal detection through the
>earth. Along with using seismic detection devices we directly
>interface with the earth and measure electrical transients between
>probes.
>
>Larry's A/D card along with the Winquake program are very useful
>when used with suitable low pass filters. Using this method the
>propagation factor is quite different and much faster. Near real
>time. One draw back however is determining quickly the distance,
>magnitude, and depth. Currently we are working on that problem
>by linking widely separated sites.
>
>Later,
>Charlie
>Elfrad Group
> 35.728N
> 80.810W
>
----- earthquake WARNING research -----
--- animals, people, scientific evidence ---
--- http://www.teleport.com/~bfryer ---
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: URL Problem w/USGS
Date: Mon, 09 Jun 1997 08:04:30 -0700
I have found recent some events posted through the IRIS-DMC at this URL:
http://www.iris.washington.edu/cgi-bin/finger?spyder@...................
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
Office Location: 39.43N 119.71W
mailto:watson@................
http://www.seismo-watch.com
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Ron Westfall <westfall@...............>
Subject: Re: URL Problem w/USGS
Date: Mon, 09 Jun 1997 09:02:35 -0700
Charles
I just checked a bit further and found out that wwwneic.cr.usgs.gov
and gldss7.cr.usgs.gov are the same server. It is not uncommon that
servers have aliases. Both of the above names appear to be aliases
while the real name is actually gldwwwneic.cr.usgs.gov <grin>.
I found the gldss7 part of the name by trying out www as the prefix
for the rest of the USGS pattern for server names [wce]r.usgs.gov.
In doing so, I found www.wr.usgs.gov (an interesting site by the
way). On that page there was an "Earthquake data link" that took me
to gldss7.cr.usgs.gov.
Ron Westfall
> I have never come across the "gldss7" server before.
> Where is it and what is it used for?
>
> Seems to duplicate the wwwneic server.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ct@....... (Charlie Thompson)
Subject: Problem w/USGS --FIXED!
Date: Mon, 09 Jun 1997 14:00:45 -0500
As of today the USGS link in question is now working again.
Many thanks to whoever fixed it. (Now I don't have to revise
my web page).
-Charlie Thompson
Buda, TX
>Charles
>
> I just checked a bit further and found out that wwwneic.cr.usgs.gov
> and gldss7.cr.usgs.gov are the same server. It is not uncommon that
> servers have aliases. Both of the above names appear to be aliases
> while the real name is actually gldwwwneic.cr.usgs.gov <grin>.
> ....<stuff deleted>
-------------------------------------------------------------------------
Charlie Thompson
WB4HVD 30.112N 97.891W
800 Elliott Ranch Rd.
Buda, TX 78610
http://www.onr.com/user/ct/ct.html
Seismic Station .BUE
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: NIEC servers are back up!
Date: Mon, 09 Jun 1997 15:07:28 -0700
NIEC servers are back up!
--
---/----
cpw
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Martin Brewer" <mbrewer@......>
Subject: Re: Move to Oregon
Date: Mon, 9 Jun 1997 19:55:41 -0300
----------
>
> Hello to all from Oregon,
> Will be getting a seismometer connected soon. I can expect a lot of wave
noise,
> and am anxious to see how bad it will be. I think it should be in the
higher
> frequencies and should be filterable. Has anyone operated a seismograph
1/2
> mile from the beach? What am I in for?
>
____________________________________________________________________________
>
> Al Allworth, Gold Beach, OR aallworth@........
Hi Al,
I have just switched on my lehman in Bermuda - half a mile from South
Shore. I am picking up a steady 3.8 sec microseismic pattern - the waves
had a period of twice that yesterday! I haven't seen an earthquake yet,
the sensor is uncalibrated until then. I would be interested to know if
you see the same sort of thing.
Regards,
Martin S. Brewer, Bermuda mbrewer@......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Phil Giannini <pgianni@.........>
Subject: Geyserville Telemetery
Date: Mon, 9 Jun 1997 16:36:56 -0700 (PDT)
Hi Gang,
I am planning to spend a few days near Geyserville during my vacation,
and thought I would try to set up a little temporary monitoring station
during my stay there. Seeing how the Geyserville area always seems to find
a spot on the daily event lists I thought I would bring a Kinemetrics SSA-2
recorder, computer and a scanner along with hopes of maybe capturing something.
I know there are some sensors scattered about in that area, but does
anyone know if their signals are telemetered by radio back to a common point
like in the bay area? If so, does any one know what the frequencies are.
Any input will be appreciated.
Thanks, Phil (SFN&Z)
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Robert L. Thomasson" <102073.3346@..............>
Subject: Accellerometer chips
Date: 09 Jun 97 20:02:06 EDT
Hello,
I read Larry Cochranes very timely warning about building a seismograph using
the ADXLO5 chips. Somewhere I read about an EG&G chip, ICS-3052, that is much
more sensitive and used by the USGS in seismographs. Can anyone tell me where I
can find more information on the ICS-3052 and will it really work in a
seismograph, or is there something inherently wrong with accellerometer chips
for use in seismographs? I'm located in Reno, NV and have already started
building the ADXL05 based device. Any advice is appreciated.
Thanks, Bob
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Accellerometer chips - ICS-30xx
Date: Mon, 9 Jun 1997 16:18:57 -0800
In response to Bob Thomasson's question on accelerometers,
this is a reposting of a message from John Evans of the USGS,
Menlo Park, CA.
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
> From null@................... Mon Jan 27 13:25 AKS 1997
> Date: Mon, 27 Jan 1997 13:26:53 -0900
> From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
> To: psn-l@.............
> Subject: Re: My thoughts on the 4/96 SA seismograph article.
>
>
> John Evans has done a lot of testing of the potential use of
> the new accelerometer chips for seismology. I asked him to
> comment on some of his findings to date. He mentions the
> SMA-1 for comparison, which is the film-recording strong-
> motion instrument that was the standard for strong motion
> seismology prior to the introduction of digital instrumentation.
>
> JCLahr
>
> ----- Begin Included Message -----
>
> From evans@.................... Wed Jan 22 11:02 AKS 1997
> To: lahr@.................
> Subject: Re: My thoughts on the 4/96 SA seismograph article.
>
> John L.,
>
> A quick response ...
>
> The ADXL-05 is better than an SMA-1 but by today's standards not very
> good. It has many mg noise (PTP) over the seismic band. It is a fair
> (but robust and temperature compensated and cheap) strong-motion
> sensor. It most certainly was vastly overhyped by the Amateur
> Scientist article. Still, it's possible to do useful and interesting
> things with it.
>
> The ones we're looking at most seriously now are the EG&G ICSensors
> (Milpitas) offerings, which are somewhat more expensive (say $50 versus
> $15 in very large quantities) and need conditioning. Their ICS-3031
> can do about 0.25 mg PTP noise from 0-35 Hz with an OP270 amp and
> LT1019 voltage reference for its Wheatstone bridge. It's pretty tough
> but highly temperature sensitive (but a thermistor and the maker's
> calibration takes that out fine). However, IDS's next-better sensor
> (the ICS-3028) reaches to urban noise levels (10-100 ug PTP). It runs
> about $100 per channel with conditioning in 500 quantities. We may
> work with PEPP to make it available to high schools as a strong-motion
> and general physics sensor, so the amateurs should keep in touch over
> the next year. More difficult to use and more expensive but a much
> more capable sensor.
>
> The next tier up is in the $300 range and not relevant to cheap
> seismology. Also pointless since we can get to the background noise
> level for $100!
>
> --John E.
>
>
> ----- End Included Message -----
>
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: New station and country
Date: Tue, 10 Jun 1997 13:37:38 +1200
Hi ya all,
Please extend a warm welcome to Martin Brewer who hails from
Bremuda.
He is in a great spot to record the Nthrn Mid-Atlantic Ridge events He
is using SDR and Winquake so it will be good to see some seismograms from
him in due course.
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Joshua Flippen <hflippen@........>
Subject: Re: URL Problem w/USGS
Date: Mon, 09 Jun 1997 21:23:49 -0500
Please unsubscribe me from this server.
_____________________________________________________________________
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From: Jean-Yves Trudel <jtrudel@.........>
Subject: Re: Accellerometer chips
Date: Tue, 10 Jun 1997 11:59:42 -0700
Robert L. Thomasson wrote:
>
> Hello,
>
> I read Larry Cochranes very timely warning about building a seismograph using
> the ADXLO5 chips. Somewhere I read about an EG&G chip, ICS-3052, that is much
> more sensitive and used by the USGS in seismographs. Can anyone tell me where I
> can find more information on the ICS-3052 and will it really work in a
> seismograph, or is there something inherently wrong with accellerometer chips
> for use in seismographs? I'm located in Reno, NV and have already started
> building the ADXL05 based device. Any advice is appreciated.
>
> Thanks, Bob
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
Hi Robert!
My name is Jean-Yves Trudel and I'am living in Quebec City Canada.
I'am a new member in the list, and I work in the avionic field.
I am interested to build a small portable seismographe and I have notice
that you found an accellerometer chip as a sensor. Even if it's not the
best, I'll be glad to start with that chip.
For a beginner like me, where can I find technical documentations, data
sheets of the sensors, and/or informations where to buy the sensors ?
Thank you very much and if you find any mistakes in my texte it's
because I'am French Canadian.
Jean-Yves Trudel
3034 rue Ratte
Lac St-Augustin
Quebec Canada
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Charles R. Patton" <patton@..........>
Subject: Re: Accelerometer chips and "jellybean" seismometers
Date: Tue, 10 Jun 1997 10:29:04 -0700
Just 2 items -- JPL accelerometer and Humphrey accelerometer
***********
JPL Accelerometer:
I wrote Dr. Paul M. Zavracky of Northeastern University re the JPL
accelerometer and possible availability of it for the amateur communi-
ty.
He kindly replied in part:
"My accelerometer program with JPL ended about two years ago. I
have since moved on to other things. It's too bad in my opinion,
since we were able to make the accelerometer they were looking for.
These devices, while small, required sophisticated processing and
were expensive to make. It took an engineer about one month to
assemble one unit. To produce one we would have to charge some-
thing on the order of $5000. With a semiconductor type process, if
you shut it down, you essentially lose it. Therefore, our costs to
restart such a process would be high and some time would be needed
to get things working properly again.
All functional units produced at Northeastern were shipped to JPL
(about 20). I believe all have been tested and damaged in one way
or another during testing."
So as I guessed, these are not likely to be available for years to
come.
***************
Humphrey accelerometer seismometer progress:
There have been several emails over the last few days inquiring
about the Analog Devices and EG&G accelerometers. At the risk of
being repetitious, please keep in mind the Humphrey accelerometer.
(see my previous posts for some numbers) Its specs are much better
than the Analog Devices unit and comparable to the best EG&G unit,
while being only $10 per channel in sensor costs. With the approach
I've taken in the Geo-Monitor seismometer project, using the Burr-
Brown ADS1213 A/D, a 20 bit resolution for 3 channels is only going to
cost about $5 a channel in additional parts not counting the power
supply. The prototype is up and limping (I only capture 45 seconds at
a time and I've set the hi-pass at 10 seconds, even though the sensor
is DC capable.) This week I intend to expand the recording time to 10
minutes and lower the cutoff frequency to 100 seconds or so. But data
to date shows approximately +- 30 ug p-p low frequency (.2 to 2 Hz
type noise on a visual plot). So in addition to the modifications
mentioned above, I need to do the mathematical analysis and the A/B
comparison between my unit and the one Erich Kern is building. When
those items are completed (probably sometime in the next two weeks),
some hard numbers will be available.
Charles R. Patton <patton@.........>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: JIM CRISTIANO <weitech@..........>
Subject: Re: Accellerometer chips
Date: Tue, 10 Jun 1997 12:46:33 -0700
Jean-Yves Trudel wrote:
>
> Robert L. Thomasson wrote:
> >
Can anyone tell me where I
> > can find more information on the ICS-3052 and will it really work in a
> > seismograph,
> For a beginner like me, where can I find technical documentations, data
> sheets of the sensors, and/or informations where to buy the sensors ?
Here's EG&G's vitals:
EG&G IC SENSORS
1701 McCarthy Blvd.
Milpitas, Ca 95035-7416
free catalog 1-800-767-1888
phone: 408-432-1800
fax: 408-432-7322
I don't see a web address in the ad.
Asta la Vista,
Jim cristiano@...........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Accelerometer chips and "jellybean" seismometers
Date: Wed, 11 Jun 1997 11:13:53 +1200
Hi you guys,
For the life of me, I cannot understand why on earth
you want to persist with these very poor response accel. chip devices when
for US$20 you can have a top class geophone seismometer and get guaranteed
great results.... Unless you want to exp. with strong motion seismology.
Dave
At 10:29 AM 6/10/97 -0700, you wrote:
>Just 2 items -- JPL accelerometer and Humphrey accelerometer
>***********
>JPL Accelerometer:
> I wrote Dr. Paul M. Zavracky of Northeastern University re the JPL
>accelerometer and possible availability of it for the amateur communi-
>ty.
> He kindly replied in part:
>
> "My accelerometer program with JPL ended about two years ago. I
> have since moved on to other things. It's too bad in my opinion,
> since we were able to make the accelerometer they were looking for.
> These devices, while small, required sophisticated processing and
> were expensive to make. It took an engineer about one month to
> assemble one unit. To produce one we would have to charge some-
> thing on the order of $5000. With a semiconductor type process, if
> you shut it down, you essentially lose it. Therefore, our costs to
> restart such a process would be high and some time would be needed
> to get things working properly again.
> All functional units produced at Northeastern were shipped to JPL
> (about 20). I believe all have been tested and damaged in one way
> or another during testing."
>
> So as I guessed, these are not likely to be available for years to
>come.
>
> ***************
>Humphrey accelerometer seismometer progress:
> There have been several emails over the last few days inquiring
>about the Analog Devices and EG&G accelerometers. At the risk of
>being repetitious, please keep in mind the Humphrey accelerometer.
>(see my previous posts for some numbers) Its specs are much better
>than the Analog Devices unit and comparable to the best EG&G unit,
>while being only $10 per channel in sensor costs. With the approach
>I've taken in the Geo-Monitor seismometer project, using the Burr-
>Brown ADS1213 A/D, a 20 bit resolution for 3 channels is only going to
>cost about $5 a channel in additional parts not counting the power
>supply. The prototype is up and limping (I only capture 45 seconds at
>a time and I've set the hi-pass at 10 seconds, even though the sensor
>is DC capable.) This week I intend to expand the recording time to 10
>minutes and lower the cutoff frequency to 100 seconds or so. But data
>to date shows approximately +- 30 ug p-p low frequency (.2 to 2 Hz
>type noise on a visual plot). So in addition to the modifications
>mentioned above, I need to do the mathematical analysis and the A/B
>comparison between my unit and the one Erich Kern is building. When
>those items are completed (probably sometime in the next two weeks),
>some hard numbers will be available.
>
>Charles R. Patton <patton@.........>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Accellerometer chips
Date: Tue, 10 Jun 1997 17:20:48 -0600
In answer to the question Robert L. Thomasson asked, "is there something
inherently wrong with accellerometer chips", I will re-post this email
on the subject.
Larry-
Last week you posted the following message:
Subject: My thoughts on the 4/96 SA seismograph article.
Date: Tue, 21 Jan 1997 21:16:41 -0700
From: Larry Cochrane <cochrane@..............>
and yesterday John Lahr responded by forwarding a message by John Evans
of the USGS regarding the characteristics of low-cost accelerometers
that he has tested. This are some of my thoughts on the subject.
I completely agree with you that if one only monitors
acceleration in the urban environment, you have to wait until hell
freezes over or a local magnitude 6 earthquake happens before you would
get any high
signal-to-noise accelerograms with nice wiggles worth looking at. Most
of the time, you would be seeing only your washing machine or the
neighbor's car driving in and out of the driveway. So it's not only a
question of sensitivity, but also a question of signal-to-noise.
Signal-to-noise is strongly controlled by the frequency band observed,
and acceleration and velocity, respectively, effectively sample
different parts of frequency band. Acceleration amplifies high
frequencies relative to low frequencies, and the velocity amplifies low
frequencies relative to high frequencies. Mathematically, the
expression for acceleration amplitude in terms of velocity as a function
of frequency is
A(f) = V(f) * 2 * pi * f
where A(f) is the acceleration amplitude (cm/s**2), V is the velocity
amplitude (cm/s), and f is frequency (Hz).
The Lehman seismometers work because there are alot of
teleseismic
events greater than magnitude 5-6 around the world that produce
relatively large ground velocities in the low-frequency band, 0.1 - 1.0
Hz, these frequencies efficiently propagate teleseismic distances (they
suffer little anelastic attenuation going through the asthenosphere),
and there is not alot of cultural noise from the neighbors in this
frequency band. However, the Lehmans will go off-scale when there is an
event large/close enough to cause local damage and be felt. Therefore,
the Lehmans will miss the most important events, the earthquakes that
have the largest impact on the community.
Strong motion seismologists, which we have all become at the
USGS (in
principle, if not in fact), are concerned about those large, relatively
infrequent local earthquakes. We need the on-scale recordings of strong
ground motions that only accelerometers can provide so that we can find
out why buildings fall down during earthquakes. The seismic engineering
rule of thumb is that the natural period of a building is equal to 0.1
seconds times the number of its floors and the fundamental resonant
frequency of the building is the reciprocal of that period, e.g., 1
floor = 0.1 s = 10 Hz, 2 floors = 0.2s = 5 Hz, etc. Buildings, like
other harmonic oscillators, respond most to and are thus most
susceptible to damage from strong ground shaking in the frequency bands
near their resonant frequencies. Most buildings are less than 10 floors
and therefore most sensitive to ground motions in the frequency band 1 -
10 Hz. However, with respect to living downtown and trying to record
weak ground motions produced by earthquakes, this frequency band is
dominated by cultural noise.
So the problem is: to record ground motions useful to study for
the
reduction of earthquake hazards, we have to use accelerometers and be
paid to be patient; but to keep members of the Public Seismic Network
(PSN) interested in operating seismographs at home, they have to record
from long period velocity sensors.
One solution is to record both velocity and acceleration simultaneously
and keep only the record that is on-scale. We do this with the USGS
GEOS 6-channel portable autonomous digital seismograph (PADS); we
record 3 channels of acceleration from an FBA-23 (force balance
accelerometer) and 3 channels of velocity from an L-22 (2 Hz geophone).
This requires twice the recording band-width. Alternatively, using
low-noise accelerometers, one could digitize and record acceleration but
then generate a velocity timeseries by digitally integrating the
acceleration timeseries. The velocity trace would be used most often
because the act of integrating effectively low-passes the original
signal and filters out much cultural noise. When a large/close
earthquake happened that produced strong ground motions, the
acceleration would still be on-scale. However, this scheme requires an
accelerometer with a range of at least 10**-6 at the low end to about
2.0 g at the high end. This corresponds to a dynamic range of about 130
dB or 21-22 bits of resolution. That is alot of umph to get out of a
low-cost accelerometer at present, so perhaps the acceleration/velocity
hybrid is the way to go in the meantime.
Robert L. Thomasson wrote:
>
> Hello,
>
> I read Larry Cochranes very timely warning about building a seismograph using
> the ADXLO5 chips. Somewhere I read about an EG&G chip, ICS-3052, that is much
> more sensitive and used by the USGS in seismographs. Can anyone tell me where I
> can find more information on the ICS-3052 and will it really work in a
> seismograph, or is there something inherently wrong with accellerometer chips
> for use in seismographs? I'm located in Reno, NV and have already started
> building the ADXL05 based device. Any advice is appreciated.
>
> Thanks, Bob
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Robert L. Thomasson" <102073.3346@..............>
Subject: Humphrey Accellerometer Chips
Date: 11 Jun 97 08:58:49 EDT
First; I'm new to this list (I'm not even sure if I spell "Accellerometer"
right) and have already received lots of help from so many people that it would
take too much space to thank everyone individually. Thanks, and I hope it won't
be too long before I can contribute and not just ask questions. I got
interested in seismology through reading the Scientific American article on the
ADXL05 chips, and although the article was somewhat misleading, it did serve to
get a lot of us interested.
Second; Charles Patton mentioned Humphrey chips and recommended reviewing his
prior posts for specifications. I don't know how to access archival posts and
don't have much in the way of archives myself since I'm a new subscriber. Can
someone provide some basic information on Humphrey chips as I'm not familiar
with the company.
Third, and last - Scientific American, as you know, also published an article on
magnetic field monitoring. Does anyone have any comments on this project? I'd
like to build it too, but I'm a little bit gunshy after my experience with
buying the ADXL05's.
Regards, Bob
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Erich Kern <73162.2364@..............>
Subject: Humphrey Accelerometers
Date: 11 Jun 97 11:26:31 EDT
Anyone who would like a data sheet on the Humphrey accelerometers please send me
your snail mail address and I'll put it in the mail. Please don't post to this
list. My e-mail address:
Erich Kern 73162.2364@..............
Anyone wanting info on seismometer application of the Humphrey accelerometer
should e-mail Charles Patton. His e-mail address: patton@.........
Regards,
Erich
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Geophones
Date: Wed, 11 Jun 1997 13:11:28 -0400
Hi gang,
Yesterday, David Nelson suggested that the interest in solid-state
accelerometers is misplaced in that commercial (and very good)
accelerometers are cheap and readliy available. These are commonly calle=
d
geophones.
A catalog of May '96 from Mitcham Industries, PO Box 1175 Huntsville, T=
X
409-291-2277 lists a bunch of used geophones, e.g., 3 Hz L15B for $25. =
Others range up to 28Hz.
RT Clark Companies PO Box 20957 Oklahoma City, OK 405-751-9696 (spring =
of
'96) offered a bunch, e.g., GS-11, 4.5Hz vertical for $40 and GS20D, 8Hz
for $12.50 and SM-4/7 30 Hz for $19.50 (they had 400 of these so don't be=
bashful).
Both these outfits seem happy to send a catalog per a 'phone request.
I have no experience with this sort of thing but they sound good.
Bob Barns
=
=
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Doug Crice <dcrice@............>
Subject: Re: Geophones
Date: Wed, 11 Jun 1997 11:44:11 -0700
Geophones and Seismometers are both "moving-coil and magnet" velocity
transducers. Traditionally, when they are used for recording
earthquakes, they are called seismometers, and when they are used for
seismic exploration (make your own event with dynamite or equivalent),
they are called geophones. As a practical matter, exploration geophones
typically have a higher natural frequency for the pendulum (say 4.5 to
40 Hz) than do seismometers (say 1 Hz).
However, geophones work well and are rugged and sensitive. You will have
no trouble amplifiying the signal until background noise shows. Since
they are velocity transducers, they are less sensitive to cultural noise
than accelerometers, and since they are passive, have virtually no noise
of their own.
The manufacturers of geophones still alive are Geospace, Input/Output
(formerly Sensor) and Mark Products. Input/Output's line is not as
broad, and Mark Products has been bought by a company that understands
accounting better than business and now they have a $1000 minimum
purchase.
An exploration geophone consists of sensing element (say 1" D x 1.5"
long), in a case, with spike base, and leads with clip leads. Mitcham
Industries and R T Clark are dealers in used geophysical equipment.
Their geophones will look like the above description.
For earthquake recording, all you need are the sensing elements, which
don't cost all that much (say $30 to $40 each). Lower frequency
geophones, the kind we care about, come in vertical and horizontal
orientations (with different springs to support and center the coil) and
if operated in the wrong orientation, the coil will bump against the
stops.
There are some 3-component geophones available on the surplus market,
and if you could pick up some of these, they would be excellent. The
lower the frequency the better for earthquakes, 4.5 Hz is probably the
lowest you will find readily, but there are some lower ones out there.
Check with Clark and Mitcham. These people normally work on bigger
sales and operate on small commissions, but they are nice guys.
Geospace has part of their catalog on the web at
http://www.geospacecorp.com/geophys.htm
Some of the folks who make vibration monitors take the 4.5 Hz geophones
and apply frequency compensation to lower the effective natural
frequency down close to earthquake range.
Doug Crice
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David Josephson <david@...............>
Subject: Re: Geophones
Date: Wed, 11 Jun 1997 15:03:04 -0700 (PDT)
On Wed, 11 Jun 1997, Doug Crice wrote:
> Geophones and Seismometers are both "moving-coil and magnet" velocity
> transducers. Traditionally, when they are used for recording
etc.
Since Doug in his typical modesty didn't introduce himself to the
list here, I'll do it for him. Doug Crice was a founder of Nimbus
Instruments in Sacramento, which pioneered the portable exploration
seismograph for refraction, shear-wave and shallow reflection work
(typically, hammer and plate for an energy source and 1 to 12 geophones).
The company was bought, founders and all, by EG&G Geometrics of Sunnyvale
where Doug was basically responsible for seismic product development
and marketing, including expansion into the bigger seismograph
market for oil exploration. Around the time EG&G sold Geometrics to
a group headed by its then general manager, Doug (and I) left. I'm
making microphones, Doug is making roll-along switches and some
other "Geostuff" and ground penetrating radar, see www.georadar.com.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Geophones
Date: Thu, 12 Jun 1997 10:22:16 +1200
WELL DONE Bob,
excellent pricing, and the same units that I am using in New
Zealand thanks for finding another source for them.....
Dave
At 01:11 PM 6/11/97 -0400, you wrote:
>Hi gang,
> Yesterday, David Nelson suggested that the interest in solid-state
>accelerometers is misplaced in that commercial (and very good)
>accelerometers are cheap and readliy available. These are commonly called
>geophones.
> A catalog of May '96 from Mitcham Industries, PO Box 1175 Huntsville, TX
>409-291-2277 lists a bunch of used geophones, e.g., 3 Hz L15B for $25.
>Others range up to 28Hz.
> RT Clark Companies PO Box 20957 Oklahoma City, OK 405-751-9696 (spring of
>'96) offered a bunch, e.g., GS-11, 4.5Hz vertical for $40 and GS20D, 8Hz
>for $12.50 and SM-4/7 30 Hz for $19.50 (they had 400 of these so don't be
>bashful).
> Both these outfits seem happy to send a catalog per a 'phone request.
> I have no experience with this sort of thing but they sound good.
>Bob Barns
>
>
>
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jim Hannon <jmhannon@........>
Subject: 3 axis seismometer
Date: Wed, 11 Jun 1997 20:50:32 -0500
A project that I have been working on for sometime is a 3 axis
seismometer that has the same response for all 3 axes. It would be
interesting to see what the 3 dimensional vector of a seismic wave looks
like. The N-S and E-W axes are no problem but the up-down is different
because of the bias of gravity. Today while staring at an aluminum cube
I keep on my desk at work I had an idea. What if one were to rotate the
coordinate system so that a set of 3 orthogonal SG type force balance
accelerometers were all oriented with the same angle with respect to
gravity? One could then rotate the coordinate system back to the
traditional orientation with some computer crunching on the sampled
data. Any comments on this hair brained idea?
--
Jim Hannon
http://soli.inav.net/~jmhannon/
42,11.90N 91,39.26W
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: 3 axis seismometer
Date: Wed, 11 Jun 1997 20:47:03 -0600
Jim-
I am impressed by your insight into the problem. There are such
3-component configuration geophones commercially available, though I
don't know who the manufacturer is/was. A colleague made some
recordings with one in 1993, and I adapted a program I had then to do
the necessary rotations into Z, N, E components. I think they are very
nifty in principle, but I have had no further experience with them.
-Edward
Jim Hannon wrote:
>
> A project that I have been working on for sometime is a 3 axis
> seismometer that has the same response for all 3 axes. It would be
> interesting to see what the 3 dimensional vector of a seismic wave looks
> like. The N-S and E-W axes are no problem but the up-down is different
> because of the bias of gravity. Today while staring at an aluminum cube
> I keep on my desk at work I had an idea. What if one were to rotate the
> coordinate system so that a set of 3 orthogonal SG type force balance
> accelerometers were all oriented with the same angle with respect to
> gravity? One could then rotate the coordinate system back to the
> traditional orientation with some computer crunching on the sampled
> data. Any comments on this hair brained idea?
> --
> Jim Hannon
> http://soli.inav.net/~jmhannon/
> 42,11.90N 91,39.26W
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
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From: Aart Olsen <aart@........>
Subject: Re: 3 axis seismometer
Date: Wed, 11 Jun 1997 21:49:59 -0500 (CDT)
I tried this arrangement with a bowling ball sitting in a triangular
"socket", using piezo sensors at the contact points. It's kinematically
elegant and and the axis rotation isn't mathematically difficult, and it
worked as a breadboarded rig. I didn't pursue it though, because having
paired piezos N-S, E-W and U-D (with a spring at the bottom to remove the
weight) is nearly as easy to do and provides an opportunity to use
differential amplification which has double the gain and lower noise.
Aart M. Olsen mailto:aart@........ 217-244-4688
Library Systems Office Univ of Illinois at Urbana-Champaign
On Wed, 11 Jun 1997, Jim Hannon wrote:
> A project that I have been working on for sometime is a 3 axis
> seismometer that has the same response for all 3 axes. It would be
> interesting to see what the 3 dimensional vector of a seismic wave looks
> like. The N-S and E-W axes are no problem but the up-down is different
> because of the bias of gravity. Today while staring at an aluminum cube
> I keep on my desk at work I had an idea. What if one were to rotate the
> coordinate system so that a set of 3 orthogonal SG type force balance
> accelerometers were all oriented with the same angle with respect to
> gravity? One could then rotate the coordinate system back to the
> traditional orientation with some computer crunching on the sampled
> data. Any comments on this hair brained idea?
> --
> Jim Hannon
> http://soli.inav.net/~jmhannon/
> 42,11.90N 91,39.26W
>
>
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
>
_____________________________________________________________________
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From: ACole65464@.......
Subject: Accelerometer Calibration, Tilt Test
Date: Wed, 11 Jun 1997 23:02:56 -0400 (EDT)
Hello Gang,
Here I go again, trying to determine the sensitivity of my force feedback
accelerometer so as to ultimately calculate the backgroud noise level at my
home. This time I did a different calibration procedure, a procedure that
some of you may have already done. I wanted to see how results using the
seismo-calibrator, of Bob Barnes' design, would compare to this other
approach. Please don't hesitate to give me some feed back if you see a
mistake along the way.
The accelerometer under test has a 4" long inverted pendulum, with a
natural period of .6 Hz and a mass of .155 Kg. Voltage output is +/- 10
volts.
The test was done by tilting the seismometer slightly either side of its
rest position along its sensitive axis. Accurate determination of the
pendulum's inclination using a machinist's dial indicator was easy to do. The
leveling screw on the instrument's sensitive axis was adjujusted to give a
+/- .005" deflection, the indicator touched the base adjacent to the screw.
As this screw was worked the instrument pivoted on the points of the 2 other
leveling screws, these are on an axis perpendicular the sens axis. The
leveling screw on the sens axis is 4.000" away from the other axis created by
the 2 other screws. Using trig the total angle of tilt (for .010" of total
travel) of the instrument was calculated to be .143239 degrees. The total
voltage range was measured as 5.400 volts (+/- 2.70 volts either side of
rest). The force to deflect the pendulum from rest due to gravity was
calculated to be:
.155 Kg for the pendulum mass X sin .143239 degrees = .00038749 Kg
To determine how much force it took to deflect the pendulum per millivolt at
the output of the seismometer then:
.00038749 Kg divided by 5400 millivolts = .000000071 Kg/Mv
Next to convert this to acceleration the above result was multipied by g. to
give:
.000000071759 Kg X 9.8m/s^2 = .000000703 m/s^2/Mv (this is at the
seismometer output)
After plugging in the chart recorder's gain into other equations to see
what this site is doing noise wise it was shown that on quiet days the
background accelrations are approximately .0000018 m/s^2. This compared
fairly well to the .0000020 m/s^2 result that I had determined earlier. The
seismo-calibrator I had made had a result being off by <5 % (higher) for the
m/s^2/Mv as measured at the seismometer output as compared to this procedure.
There are other ways to guage instrument tilt than using a dial indicator.
Just use shims under the sensitivity adjusting screw for example. This was an
another interesting project and done in an hour.
Like I said before, let me know where I may have messed up.
Bye for now,
Allan Coleman, Seattle
_____________________________________________________________________
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From: Barry Lotz <gbl@.......>
Subject: Re: 3 axis seismometer
Date: Wed, 11 Jun 1997 19:47:06 -0700
Hi Jim
Sorry I didn't understand what you were rotating? I have thought in
the past that one could "focus" the three waves and get an event
direction .I haven't had much luck in that regard though. I believe the
P and S waves are in orthogonal directions.
Barry
>Jim Hannon wrote:
>
> A project that I have been working on for sometime is a 3 axis
> seismometer that has the same response for all 3 axes. It would be
> interesting to see what the 3 dimensional vector of a seismic wave looks
> like. The N-S and E-W axes are no problem but the up-down is different
> because of the bias of gravity. Today while staring at an aluminum cube
> I keep on my desk at work I had an idea. What if one were to rotate the
> coordinate system so that a set of 3 orthogonal SG type force balance
> accelerometers were all oriented with the same angle with respect to
> gravity? One could then rotate the coordinate system back to the
> traditional orientation with some computer crunching on the sampled
> data. Any comments on this hair brained idea?
> --
> Jim Hannon
> http://soli.inav.net/~jmhannon/
> 42,11.90N 91,39.26W
>
_____________________________________________________________________
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From: Doug Crice <dcrice@............>
Subject: Re: 3 axis seismometer
Date: Wed, 11 Jun 1997 22:23:12 -0700
Pretty creative.
A Russian did this many years ago with geophones. He mounted three
geophones each inclined I believe 57.5 degrees from the vertical which
turns out to be an X-Y-Z orientation balanced on its corner. This
arrangement is known worldwide as the "Galperin" orientation. Galperin
is famous for developments in Vertical Seismic Profiling (petroleum
exploration seismic using a geophone down a borehole for improved
imaging) and his book was translated into English and published by the
Society of Exploration Geophysicists.
However, the real advantage of the Galperin array was that the three
geophones could be identical in design, and thus have matched response,
necessary to do a good job on the rotation of the vectors. The
orientation never was very popular in the U.S. because the American
companies were able to make vertical and horizontal geophones with
matched response characteristics and a conventional XYZ orientation is a
lot smaller diameter.
In the case of accelerometers, the vertical one would have a 1 g bias or
offset voltage which could normally be easily filtered out. It does
constrain you to a 0 to 2 g full scale range though, which implies less
than maximum sensitivity. Of course leaning all three over still gives
you most of a g bias.
Doug Crice
Jim Hannon wrote:
>
> A project that I have been working on for sometime is a 3 axis
> seismometer that has the same response for all 3 axes. It would be
> interesting to see what the 3 dimensional vector of a seismic wave looks
> like. The N-S and E-W axes are no problem but the up-down is different
> because of the bias of gravity. Today while staring at an aluminum cube
> I keep on my desk at work I had an idea. What if one were to rotate the
> coordinate system so that a set of 3 orthogonal SG type force balance
> accelerometers were all oriented with the same angle with respect to
> gravity? One could then rotate the coordinate system back to the
> traditional orientation with some computer crunching on the sampled
> data. Any comments on this hair brained idea?
> --
> Jim Hannon
> http://soli.inav.net/~jmhannon/
> 42,11.90N 91,39.26W
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
_____________________________________________________________________
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From: Doug Crice <dcrice@............>
Subject: Geophones
Date: Thu, 12 Jun 1997 12:34:03 -0700
I sorry to keep burdening you guys with geophone discourse, but I just
noticed that Mitcham Industries has a home page with their list of used
geophones for sale:
http://www.mitchamindustries.com/cgi-bin/dbml.exe?template=/mitcham/catalog&cid=11&cart=
If that doesn't work start at www.mitchamindustries.com and work your
way to the used geophone page.
It's not obvious on the list, but the petroleum explorationists
typically use strings of geophones, in other words, there might be 6 or
12 vertical geophones wired together in a long string. So when you see
the note 6/ or 12/ or such, it means a bunch of geophones. When you see
the words "single phone string", or 1/ there is just one geophone. You
will also find some 3-component or triaxial packages which are of course
3 geophones in a single case in X-Y-Z form. When you see "shear wave"
or "horizontal" that means the geophones have the right springs so they
operate in the horizontal orientation. If the orientation is not
listed, they are vertical, the most common by far.
R. T. Clark (phone 405-751-9696, fax 405-751-6711) has just issued a new
catalog with some 8 Hz geophone elements at $8 each. Also some 1 Hz
Mark Products L-4C seismometers @ $375. That's a bit steep for the
hobbyist, but these are real seismometers and everything's negotiable.
He even has a Sprengnether MEQ-800 drum recordering seismograph listed
at $2000.
Doug Crice
_____________________________________________________________________
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From: Edward Cranswick <cranswick@........>
Subject: Re: 3 axis seismometer
Date: Thu, 12 Jun 1997 17:38:01 -0600
Doug-
When I was in the Soviet Union I never saw such geophones, but I
subsequently met a young Russian who used some Russian geophones of that
design for a study in Iceland, but I spaced that out and didn't realize
that they were a Russian invention in the first place.
-Edward
Doug Crice wrote:
>
> Pretty creative.
>
> A Russian did this many years ago with geophones. He mounted three
> geophones each inclined I believe 57.5 degrees from the vertical which
> turns out to be an X-Y-Z orientation balanced on its corner. This
> arrangement is known worldwide as the "Galperin" orientation.
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
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From: "Martin Brewer" <mbrewer@......>
Subject: Unknown 'quake
Date: Thu, 12 Jun 1997 21:35:43 -0300
Hi everyone,
Did anyone record an earthquake with an origin about 02:02 UTC on 12 June
1997? The Bermuda station recorded what appears to be an event about 7.6
degrees from Bermuda (850 km, 530 miles). This is the first probable
seismogram recorded at the station. If it has been recorded elsewhere I
would like to use the magnitude value to calibrate the system.
Regards,
Martin Brewer
_____________________________________________________________________
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From: David A Nelson <dann@........>
Subject: Re: Unknown 'quake
Date: Fri, 13 Jun 1997 13:04:35 +1200
Martin ,
nothing on the USGS world list for that time maybe it was
something out in the Atlantic not noted by the USGS etc.
E-mail me a copy of the SDR file so I view it in winquake
Dave
At 09:35 PM 6/12/97 -0300, you wrote:
>Hi everyone,
>
>Did anyone record an earthquake with an origin about 02:02 UTC on 12 June
>1997? The Bermuda station recorded what appears to be an event about 7.6
>degrees from Bermuda (850 km, 530 miles). This is the first probable
>seismogram recorded at the station. If it has been recorded elsewhere I
>would like to use the magnitude value to calibrate the system.
>Regards,
>Martin Brewer
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
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From: Edward Cranswick <cranswick@........>
Subject: Re: Accelerometer Calibration, Tilt Test
Date: Thu, 12 Jun 1997 19:21:47 -0600
Allan-
I believe that you can simplify your calculation of the sensitivity as
follows:
0.005/4.0 = sin (inclination angle) = 0.00125 = s
The corresponding component of gravitational acceleration, a, that tends
to deflect the the pendulum is:
a = s * g (* = multiply)
a = 0.00125 * 9.8 = 0.01225 m/s^2
This acceleration input corresponds to a voltage output of 2.70 V,
hence, the sensitivity, c, volts per acceleration, is given by:
c = 2.7/0.01225 = 220.4 V/(m/s^2)
or by your convention:
1/c/1000 = 0.000004537 (m/s^2)/mV = acceleration per milliVolt.
The mass, 0.155 Kg, does not enter into the calculation. If you
multiply the value you calculated, 0.000000703, by 0.155 to remove the
inclusion of the mass, the result is the value above, 0.000004537. I
have possibly made some errors, please check it out.
Note: period is the length of time for one cycle and is measured in
seconds (s) and frequency is the number of cycles in one second and is
measured in Hertz (Hz).
-Edward
ACole65464@....... wrote:
>
> Hello Gang,
> Here I go again, trying to determine the sensitivity of my force feedback
> accelerometer so as to ultimately calculate the backgroud noise level at my
> home. This time I did a different calibration procedure, a procedure that
> some of you may have already done. I wanted to see how results using the
> seismo-calibrator, of Bob Barnes' design, would compare to this other
> approach. Please don't hesitate to give me some feed back if you see a
> mistake along the way.
> The accelerometer under test has a 4" long inverted pendulum, with a
> natural period of .6 Hz and a mass of .155 Kg. Voltage output is +/- 10
> volts.
> The test was done by tilting the seismometer slightly either side of its
> rest position along its sensitive axis. Accurate determination of the
> pendulum's inclination using a machinist's dial indicator was easy to do. The
> leveling screw on the instrument's sensitive axis was adjujusted to give a
> +/- .005" deflection, the indicator touched the base adjacent to the screw.
> As this screw was worked the instrument pivoted on the points of the 2 other
> leveling screws, these are on an axis perpendicular the sens axis. The
> leveling screw on the sens axis is 4.000" away from the other axis created by
> the 2 other screws. Using trig the total angle of tilt (for .010" of total
> travel) of the instrument was calculated to be .143239 degrees. The total
> voltage range was measured as 5.400 volts (+/- 2.70 volts either side of
> rest). The force to deflect the pendulum from rest due to gravity was
> calculated to be:
> .155 Kg for the pendulum mass X sin .143239 degrees = .00038749 Kg
> To determine how much force it took to deflect the pendulum per millivolt at
> the output of the seismometer then:
> .00038749 Kg divided by 5400 millivolts = .000000071 Kg/Mv
> Next to convert this to acceleration the above result was multipied by g. to
> give:
> .000000071759 Kg X 9.8m/s^2 = .000000703 m/s^2/Mv (this is at the
> seismometer output)
> After plugging in the chart recorder's gain into other equations to see
> what this site is doing noise wise it was shown that on quiet days the
> background accelrations are approximately .0000018 m/s^2. This compared
> fairly well to the .0000020 m/s^2 result that I had determined earlier. The
> seismo-calibrator I had made had a result being off by <5 % (higher) for the
> m/s^2/Mv as measured at the seismometer output as compared to this procedure.
> There are other ways to guage instrument tilt than using a dial indicator.
> Just use shims under the sensitivity adjusting screw for example. This was an
> another interesting project and done in an hour.
> Like I said before, let me know where I may have messed up.
> Bye for now,
> Allan Coleman, Seattle
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
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From: Jim Hannon <jmhannon@........>
Subject: Re: 3 axis seismometer
Date: Thu, 12 Jun 1997 22:35:56 -0500
I want to thank everyone for there comments on my 3 axis seismometer
idea. It looks like the idea is worth persuing further.
--
Jim Hannon
http://soli.inav.net/~jmhannon/
42,11.90N 91,39.26W
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From: dean sevold <dsevold@..............>
Subject: Re: New Unknown 'quake
Date: Fri, 13 Jun 97 09:42:44 PDT
Hi
We're looking for info on the quake in the Vancouver, B.C. area this morn=
ing at 6:50AM PDT . We heard of it on the radio, but could find nothing =
on the net.
Looking at all the wrong websites????
Thanks,
Terry
dsevold@..............
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Public Seismic Network Mailing List (PSN-L)
From: Mike Stickney <mike@.................>
Subject: Vancouver quake
Date: Fri, 13 Jun 97 12:59:45 MDT
Here is the press release from the Pacific Geoscience Center.
-Mike Stickney
Montana Bureau of Mines and Geology
=============================================================
Department of Natural Ministere des Ressources
Resources Canada Naturelles Canada
EARTHQUAKE REPORT
GEOLOGICAL SURVEY OF CANADA
PACIFIC GEOSCIENCE CENTRE
SIDNEY, B.C.
Tel (250) 363-6500
Fax (250) 363-6565
DATE: Friday, June 13, 1997
TIME: 06:44:37 am PDT (13:44 UTC)
PRELIMINARY MAGNITUDE: 3.4
LOCATION: Strait of Georgia, B.C.
(49.24 N, 123.62 W, depth 3.5 km)
ADDITIONAL INFORMATION:
This earthquake is located in the Strait of Georgia about mid-way between
Nanaimo and Bowen Island. Initial reports indicate the quake was felt
strongly along the Sunshine Coast north of Vancouver. It was also felt
throughout the greater Vancouver area and on eastern Vancouver Island from
Nanaimo to Victoria.
No damage has been reported and none would be expected for an earthquake of
this size.
prepared by: Robert Horner, Seismologist
Canada
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From: Lucas Haag <lhaag@..............>
Subject: Re: Geophones
Date: Fri, 13 Jun 97 16:10:43 CDT
Another Question:
How can you look at and/or record the waveform patterens.
Thanks,
Lucas Haag
At 01:11 PM 6/11/97 -0400, you wrote:
>Hi gang,
> Yesterday, David Nelson suggested that the interest in solid-state
>accelerometers is misplaced in that commercial (and very good)
>accelerometers are cheap and readliy available. These are commonly called
>geophones.
> A catalog of May '96 from Mitcham Industries, PO Box 1175 Huntsville, TX
>409-291-2277 lists a bunch of used geophones, e.g., 3 Hz L15B for $25.
>Others range up to 28Hz.
> RT Clark Companies PO Box 20957 Oklahoma City, OK 405-751-9696 (spring of
>'96) offered a bunch, e.g., GS-11, 4.5Hz vertical for $40 and GS20D, 8Hz
>for $12.50 and SM-4/7 30 Hz for $19.50 (they had 400 of these so don't be
>bashful).
> Both these outfits seem happy to send a catalog per a 'phone request.
> I have no experience with this sort of thing but they sound good.
>Bob Barns
>
>
>
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
************************************************
Lucas Haag
HCR 66 Box 25A
Bartley, Nebraska 69020-9717
Email: lhaag@.............. OR haag_cnslt@...........
World Wide Web: http://www.swnebr.net/~lhaag
************************************************
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From: Seism0man@.......
Subject: Re: Geophones
Date: Fri, 13 Jun 1997 17:41:14 -0400 (EDT)
Thank you for that information on the geophones. I am in the process of
designing a very small and cheap seismograph that fits into a peice of 8 inch
PVC pipe. the geophone and the electronics package all fit inside the pipe
and need to be buried. I was having trouble finding these geophones though
and your info has made my first prototype possible. Thanks Again.
_____________________________________________________________________
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From: Jean-Yves Trudel <jtrudel@.........>
Subject: Richter & Mercalli scale
Date: Fri, 13 Jun 1997 17:46:45 -0700
Hi everybody!
I have read the A/D System Dynamic Range by Larry Cochrane.
After that, I try to find on the net the definition of an ML unit. I
understand that 2 ml to 6 ml would be a 80db or a diff. of 10K. But
where I can find the definition of ML ? Is it a unit of Mercalli if it
is, whats the difference between Richter and Mercalli. What is the
standard because in my search I found that Japan the Europeen, UK have
different interpretation.
In other words I would like to know in a level 2 on Richter this
correspond physically to how high the amplitude of the ground wave if we
monitor the z axis? what will be the time between 2 peaks on the y or x
axis etc..?
Is somebody can help me on that? or informe me where to look for the
information.
Tks!
Jean-Yves Trudel
Quebec City Canada
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From: Edward Cranswick <cranswick@........>
Subject: Re: Geophones
Date: Fri, 13 Jun 1997 16:06:49 -0600
Sounds very interesting. I look forward to hearing more.
-Edward
Seism0man@....... wrote:
>
> Thank you for that information on the geophones. I am in the process of
> designing a very small and cheap seismograph that fits into a peice of 8 inch
> PVC pipe. the geophone and the electronics package all fit inside the pipe
> and need to be buried. I was having trouble finding these geophones though
> and your info has made my first prototype possible. Thanks Again.
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
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From: JIM CRISTIANO <weitech@..........>
Subject: Re: Geophones
Date: Fri, 13 Jun 1997 16:27:25 -0700
Lucas Haag wrote:
>
> Another Question:
> How can you look at and/or record the waveform patterens.
> Thanks,
> Lucas Haag
Lucas,
A geophone is a magnet/coil combo just like the horseshoe
magnet/selinoid coil
combo, only in a nice, neat sealed package. It hooks right up to your
amp
board.
Jim cristiano@...........
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From: "Robert L. Thomasson" <102073.3346@..............>
Subject: Sensors
Date: 13 Jun 97 19:39:20 EDT
I have another entry level question: According to what I understand, mainly
from following this forum, seismic sensors should have a low natural frequency
of about 1 Hz, which I undersand is close to the natural frequency of earthquake
motion.
I have some limited experience with industrial vibration monitoring ( vibration
in turbines, pumps and pipelines) and if I'm not mistaken and I very well could
be, to avoid overexcitation of our sensors we try to use sensors that have
natural frequencies that are much higher than the frequencies we are interested
in measuring.
What am I missing here?
I live in Reno, relatively near to the SF Bay and also Mammoth, so I am
interested in both strong motion and teleseismic monitoring. I'll probably be
building both types of devices, along with a magnetic field sensor. I'll
somehow try and keep up with the house payments too.
Thanks, Bob
Thanks, Bob
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From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: Richter & Mercalli scale
Date: Fri, 13 Jun 1997 15:56:26 -0800
>Jean-Yves writes "where I can find the definition of ML ?"
I have some basic information on the Richter magnitude scale
on my web site, which is noted below.
Hope this is a good starting point for you.
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Doug Crice <dcrice@............>
Subject: Re: Richter & Mercalli scale
Date: Fri, 13 Jun 1997 16:56:30 -0700
Regarding Richter and Mercali scales and Energy:
Since you have all figured out by now that I am an old timer, I will
further embarass myself with the following anecdote that I was told by a
Seismologist back in 1964.
Charles Richter had a seismograph in his bedroom (not unlike many of
you, I suppose). When an earthquake occured, he would get up and read
the seismogram. Then, the reporters would call up and ask him how big
was the earthquake. For a while, he got away with descriptive terms
like big, medium, and small. He soon got tired of such loose terms and
developed the Richter magnitude scale, which was the logrithm of the pen
deflection on his bedroom seismograph, corrected for distance from the
earthquake. Ever since, seismographs have had to be corrected to match
the response of Richter's bedroom seismograph.
Is the anecdote true? I was young when I heard it and gullible. If
anybody can verify this story either way, I would like to know.
The Mercali scale is a measurement of damage. You will find it in any
basic seismology books. I like the terms like "some people run
outdoors" and "everybody runs outdoors" as measurements of local ground
shaking. Damage, of course, depends on building types and soil types,
and the Mercali scale can vary considerably in the same local area.
Neither is related to energy. The Richter scale is a measurement of
"peak particle velocity", whereas energy is proportional to the square
of velocity.
Doug Crice
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Richter & Mercalli scale
Date: Sat, 14 Jun 1997 12:44:51 +1200
Jean-Yves,
you are getting confused between magnitude measurement
and shaking intensity measurement
ML (this is THE ORIGINAL Richter magnitude) is a quake magnitude
measurement devised by Charles Richter in 1935. Richter defined ML "as
the logarithm to base 10 ofthe maximum seismic wave amplitude (in
thousandths of a millimetre) recordedd on a standard seismograph at a
distance of 100 km from the quake epicentre. Using the log. scale, every
time the magnitude goes up by 1 unit, the amplitude of the quake wave
increases by 10 times. ie if a ML 5.0 at 100 km produces 5mm of
amplitude on the seismograph then a ML 6.0 will produce 50mm of amplitude.
The standard seismometer used for this is the Wood Anderson seismometer.
Richter also developer a method for making allowances for attenuation with
epicentral distance when calc. the Richter Mag. of the quake.
Originally the Definition of ML was for Southern California quakes only.
The Type of seismic wave to be used was not specified; the only condition
was, that the wave chosen ---- whether the P, S, or surface wave be the
one with the largest amplitude. Richter wrote.... "I did the work to
provide a purely instrumental scale for ROUGH separation of large, medium
and small shocks.
The Modified Mercalli Scale is a felt intensity scale (from 1 to 12). is was
developed in 1902 by the Itilian seismologist G. Mercalli and was a refined
version of the original scale developed by M.S. de Rossi and Francois Forel
in the 1880's (from I to X). The intensity scale is very subjective to
local conditions, ground conditions, quality of building design etc. It
also gives no idea of the magnitude, as a small local event could give a MM6
just as easily as a larger distant event.
Dave
At 05:46 PM 6/13/97 -0700, you wrote:
>
>
>Hi everybody!
>
>I have read the A/D System Dynamic Range by Larry Cochrane.
>
>After that, I try to find on the net the definition of an ML unit. I
>understand that 2 ml to 6 ml would be a 80db or a diff. of 10K. But
>where I can find the definition of ML ? Is it a unit of Mercalli if it
>is, whats the difference between Richter and Mercalli. What is the
>standard because in my search I found that Japan the Europeen, UK have
>different interpretation.
>
>In other words I would like to know in a level 2 on Richter this
>correspond physically to how high the amplitude of the ground wave if we
>monitor the z axis? what will be the time between 2 peaks on the y or x
>axis etc..?
>
>Is somebody can help me on that? or informe me where to look for the
>information.
>
>Tks!
>
>Jean-Yves Trudel
>Quebec City Canada
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: Richter & Mercalli scale
Date: Fri, 13 Jun 1997 16:49:59 -0800
Hi Doug,
Interesting story about Richter's seismograph. The Wood Anderson units
usually had photographic recording, which would take a while to develop,
but it's possible he had a pen version at his home. Maybe someone from
CalTech can clear this up.
Although the Richter magnitude was not developed with energy in mind, it
does turn out that each increase of one unit on the Richter scale
corresponds to an increase of a factor of ~30 in energy. As I mentioned,
some of this information is on my web page.
JCLahr
################################## John C. Lahr
################################# Seismologist
################################ U.S. Geological Survey
############################### c/o Geophysical Institute
############################## 903 Koyukuk Drive
~~~~~~~~~~~~~~ Get ~~~~~~~~~~ #############################
###########################################################
P.O. Box 757320 ################################
Fairbanks, AK 99775 #################################
Phone: (907) 474-7997 ##################################
Fax: (907) 474-5618 ~~~~~~~~ the thrust? ~~~~~~~~~~~~~~
lahr@........ ####################################
http://www.aeic.alaska.edu/Input/lahr/
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Map alterations
Date: Sat, 14 Jun 1997 12:58:02 +1200
Hi all,
To appease the natives in California I spent many hours last nite
reworking the PSN map.
I now has a much larger California inset so that the Calif. stations are
not so crowded.
the map now fits the full width of the browser page and is only 6kb larger
in size 59kb v's 53kb
If I compress it any more the quality really starts to get compromised.
The original pure 24 bit file is 297kb in size.
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "John Hernlund" <69277@..................>
Subject: displacement or velocity?
Date: Fri, 13 Jun 1997 18:12:06 -0700 (MST)
> Neither is related to energy. The Richter scale is a measurement of
> "peak particle velocity", whereas energy is proportional to the square
> of velocity.
I am sorry (I am new to this stuff) but I always thought (or was told)
the Richter magnitude was a measurement of maximum ground displacement
from rest. The rate of change of the displacement would then give you the
velocity, from which the energy could be calculated using a wave analysis
technique... If I am wrong can somebody please send me a derivation of
whatever it really is that richter magnitude actually measures?
John Hernlund
69277@..................
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Sensors
Date: Fri, 13 Jun 1997 17:31:01 -0700
Hi Bob
I'm from just over the "hill". Just some thoughts-- . Natural
frequency of instrument depends on what you are measuring. For
acceleration(via deflection) you want the sensor to have a natural
frequency higher than any event frequencies.I'm not sure where
Force-Balance sensors fit in. With F-B sensors you measure the force
required to keep the mass in position when an event tries to move it.
For velocity type sensors(lehman-coil/magnet) you want a sensor with a
natural freq lower than any event frequency. I think it is intuitive if
you look at extremes. With a Lehman, in theory, the sensor stays in at
rest and the ground moves. With acceleration you are measuring the force
imposed on the mass. The acceleration spectrum seems to have higher
frequencies than velocity spectrum. Also the earth acts like a filter in
that higher frequencies are attenuated faster than lower ones with
distance from source.Quite a bit can also be done in electronics and
software to get a desired system.
Regards
Barry
Robert L. Thomasson wrote:
>
> I have another entry level question: According to what I understand, mainly
> from following this forum, seismic sensors should have a low natural frequency
> of about 1 Hz, which I undersand is close to the natural frequency of earthquake
> motion.
>
> I have some limited experience with industrial vibration monitoring ( vibration
> in turbines, pumps and pipelines) and if I'm not mistaken and I very well could
> be, to avoid overexcitation of our sensors we try to use sensors that have
> natural frequencies that are much higher than the frequencies we are interested
> in measuring.
>
> What am I missing here?
>
> I live in Reno, relatively near to the SF Bay and also Mammoth, so I am
> interested in both strong motion and teleseismic monitoring. I'll probably be
> building both types of devices, along with a magnetic field sensor. I'll
> somehow try and keep up with the house payments too.
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Barry Lotz <gbl@.......>
Subject: Re: Geophones
Date: Fri, 13 Jun 1997 17:38:12 -0700
Hi Jim
I had an interesting occurance last night. During a lightning storm
one particularily close bolt toasted the instrumentation amp connected
to my Lehman coil. I got sloppy and neglected to include clamping diodes
at the coil. I didn't think the electomagnetic field would would affect
my "shielded" sensor that much.
Barry
JIM CRISTIANO wrote:
>
> Lucas Haag wrote:
> >
> > Another Question:
> > How can you look at and/or record the waveform patterens.
> > Thanks,
> > Lucas Haag
>
> Lucas,
>
> A geophone is a magnet/coil combo just like the horseshoe
> magnet/selinoid coil
> combo, only in a nice, neat sealed package. It hooks right up to your
> amp
> board.
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: watson@................ (Charles Watson)
Subject: Re: Sensors
Date: Fri, 13 Jun 1997 21:12:37 -0700
Hey Bob!
Let me know when you get it built. I am over here in the Virgina
Foothills and would like to see it.
--
---/----
Charles P. Watson, Consulting Geologist
Advanced Geologic Exploration
Seismo-Watch / Earthquake Information Services
Voice: 702-852-0992 / Fax: 702-852-3226
Office Location: 39.43N 119.71W
mailto:watson@................
http://www.seismo-watch.com
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Stephen Caruso <scaruso@......................>
Subject: Clamping diodes?
Date: Sat, 14 Jun 1997 08:40:02 -0400 (EDT)
Bary Lotz suggested the use of clamping diodes. What are these and what
is there equivalent component number?
STEPHEN CARUSO CET
KB8UGH
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: roger baker <rcbaker@........>
Subject: Re: Clamping diodes?
Date: Sat, 14 Jun 1997 08:55:58 -0500 (CDT)
Friends,
Just about any pair of small generic diodes should work when
connected in opposite directions across a sensor output since they do not
conduct in one direction and start conducting exponentially at a few tenths
of a volt in the other direction. A pair will thus chop off any input signal
below one volt in either polarity without affecting small voltage signals.
Back to back zener diodes will simularly protect against higher
voltages--say six volts or whatever their breakdown voltage. A neon bulb
can be used to protect against surges in either direction that exceed
maybe 80 volts, and they used to be used in this way to protect geophone
windings that had maybe a quarter million turns and could generate enough
voltage to break down their own insulation if jolted.
--Yours, Roger
On Sat, 14 Jun 1997, Stephen Caruso wrote:
> Bary Lotz suggested the use of clamping diodes. What are these and what
> is there equivalent component number?
>
> STEPHEN CARUSO CET
> KB8UGH
>
>
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.......>
Subject: Re: Clamping diodes?
Date: Sat, 14 Jun 1997 11:22:02 -0700
Hi Folks --
Roger Baker wrote a good description of how to use clamping diodes.
I'd just like to clarify one point, however: If you are using signal
diodes, put them in parallel (anode of one connected to the cathode of the
other); if you are using zener diodes, put them is series (cathode to
cathode, or anode to anode).
Karl Cunningham
La Mesa, CA.
karlc@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Richter & Mercalli scale
Date: Sat, 14 Jun 1997 20:51:00 -0600
Doug-
Last time I slept next to my seismograph was when I was investigating
aftershocks of the 25 & 27 May 1980 Mammoth Lakes, California,
Earthquakes. It was a smoked drum recorder in my motel room, and I had
the jug (geophone) outside the window.
I believe that the magnitude is calculated from the peak pendulum
displacement of a Wood-Anderson seismograph which is roughly
proportional to the "peak particle displacement" of the ground at
periods lower than the 0.8 s natural period, i.e., frequencies greater
than 1.25 Hz.
I wrote code to display Nimbus data with my software when I was at USGS
Menlo Park in the early 1980s.
-Edward
Doug Crice wrote:
>
> Regarding Richter and Mercali scales and Energy:
>
> Since you have all figured out by now that I am an old timer, I will
> further embarass myself with the following anecdote that I was told by a
> Seismologist back in 1964.
>
> Charles Richter had a seismograph in his bedroom (not unlike many of
> you, I suppose). When an earthquake occured, he would get up and read
> the seismogram. Then, the reporters would call up and ask him how big
> was the earthquake. For a while, he got away with descriptive terms
> like big, medium, and small. He soon got tired of such loose terms and
> developed the Richter magnitude scale, which was the logrithm of the pen
> deflection on his bedroom seismograph, corrected for distance from the
> earthquake. Ever since, seismographs have had to be corrected to match
> the response of Richter's bedroom seismograph.
>
> Is the anecdote true? I was young when I heard it and gullible. If
> anybody can verify this story either way, I would like to know.
>
> The Mercali scale is a measurement of damage. You will find it in any
> basic seismology books. I like the terms like "some people run
> outdoors" and "everybody runs outdoors" as measurements of local ground
> shaking. Damage, of course, depends on building types and soil types,
> and the Mercali scale can vary considerably in the same local area.
>
> Neither is related to energy. The Richter scale is a measurement of
> "peak particle velocity", whereas energy is proportional to the square
> of velocity.
>
> Doug Crice
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Map alterations
Date: Sat, 14 Jun 1997 20:58:25 -0600
Dave-
The map looks good, though the Californian natives are taking over more
and more real estate (they are all over Golden and the rest of
Colorado), perhaps you have to implement zooming (not "zoning")
sometime/somehow.
-Edward
David A Nelson wrote:
>
> Hi all,
> To appease the natives in California I spent many hours last nite
> reworking the PSN map.
> I now has a much larger California inset so that the Calif. stations are
> not so crowded.
>
> the map now fits the full width of the browser page and is only 6kb larger
> in size 59kb v's 53kb
> If I compress it any more the quality really starts to get compromised.
> The original pure 24 bit file is 297kb in size.
>
> Dave
> Dave A. Nelson
>
> 24 Jensen St.,
> Green Is., Dunedin,
> South Is.. New Zealand.
>
> http://psn.quake.net/dave/home.htm
>
> Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
> Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
> THE DIRECTION OF THE MOST DAMAGE
> Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: displacement or velocity?
Date: Sat, 14 Jun 1997 21:04:46 -0600
John-
Local magnitude (ML) is proportional to the peak pendulum displacement,
not the peak ground displacement, i.e., without correction for the
complex response of a damped harmonic oscillator, the Wood-Anderson
seismograph with a 0.8 s natural period.
-Edward
John Hernlund wrote:
>
> > Neither is related to energy. The Richter scale is a measurement of
> > "peak particle velocity", whereas energy is proportional to the square
> > of velocity.
>
> I am sorry (I am new to this stuff) but I always thought (or was told)
> the Richter magnitude was a measurement of maximum ground displacement
> from rest. The rate of change of the displacement would then give you the
> velocity, from which the energy could be calculated using a wave analysis
> technique... If I am wrong can somebody please send me a derivation of
> whatever it really is that richter magnitude actually measures?
>
> John Hernlund
> 69277@..................
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re:california
Date: Sun, 15 Jun 1997 17:40:46 +1200
Ed,
I'm fully convinced that these here jokers from Californ i a have
a secret agenda for world domination (hi hi) but not if I can stop them....
I will probably accept a few ( 2-3 ) more stations onto the USA part of
the map and then seriously look at the probability of clicking anywhere on
Nth America will load up a separate full screen USA map
I will hold off as long as possible as all this activity is slowly but
surely chewing through more and more Kbytes of HDD space on Larry's computer
Dave
At 08:58 PM 6/14/97 -0600, you wrote:
>Dave-
> The map looks good, though the Californian natives are taking over more
>and more real estate (they are all over Golden and the rest of
>Colorado), perhaps you have to implement zooming (not "zoning")
>sometime/somehow.
>-Edward
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "John Hernlund" <69277@..................>
Subject: standards?
Date: Sun, 15 Jun 1997 00:05:26 -0700 (MST)
> John-
> Local magnitude (ML) is proportional to the peak pendulum displacement,
> not the peak ground displacement, i.e., without correction for the
> complex response of a damped harmonic oscillator, the Wood-Anderson
> seismograph with a 0.8 s natural period.
Okay, so is there a standard seismograph somewhere that everyone in the
world calibrates their seismograph with? This seems very strange to me.
How difficult would it be to find the energy released in Joules and the
particle motion everywhere around the focus knowing the elastic properties
of the rocks/material and having a good approximation of ground
displacement as a function of time at the epicenter?
_____________________________________________________________________
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From: lahr@................. (Dr. John Lahr (USGS-GI Seismologist))
Subject: Re: displacement or velocity?
Date: Sat, 14 Jun 1997 23:53:29 -0800
John-
Local magnitude (ML) is proportional to the peak pendulum displacement,
not the peak ground displacement, i.e., without correction for the
complex response of a damped harmonic oscillator, the Wood-Anderson
seismograph with a 0.8 s natural period.
-Edward
True, true. At frequencies above 1.25 Hz, as you mention, this is
the same thing, to the first approximation of course.
JCLahr
_____________________________________________________________________
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From: "Norm L'Heureux" <normlheureux@..............>
Subject: Re: Clamping diodes?
Date: Sun, 15 Jun 1997 16:04:35 -0700
1N914 or 1N4148 should be O.K.
roger baker wrote:
>
> Friends,
> Just about any pair of small generic diodes should work when
> connected in opposite directions across a sensor output since they do not
> conduct in one direction and start conducting exponentially at a few tenths
> of a volt in the other direction. A pair will thus chop off any input signal
> below one volt in either polarity without affecting small voltage signals.
> Back to back zener diodes will simularly protect against higher
> voltages--say six volts or whatever their breakdown voltage. A neon bulb
> can be used to protect against surges in either direction that exceed
> maybe 80 volts, and they used to be used in this way to protect geophone
> windings that had maybe a quarter million turns and could generate enough
> voltage to break down their own insulation if jolted.
> --Yours, Roger
>
> On Sat, 14 Jun 1997, Stephen Caruso wrote:
>
> > Bary Lotz suggested the use of clamping diodes. What are these and what
> > is there equivalent component number?
> >
> > STEPHEN CARUSO CET
> > KB8UGH
> >
> >
> >
> > _____________________________________________________________________
> >
> > Public Seismic Network Mailing List (PSN-L)
> >
> > To leave this list email listserver@............. with the body of the
> > message: leave PSN-L
> >
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
_____________________________________________________________________
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From: Larry Cochrane <cochrane@..............>
Subject: Re: Geophones
Date: Sun, 15 Jun 1997 23:01:38 -0700
At 04:10 PM 6/13/97 CDT, Lucas Haag wrote:
>Another Question:
>How can you look at and/or record the waveform patterens.
>Thanks,
>Lucas Haag
Besides the sensor you will need an amplifier/filter board and then some
sort of display. This can be a chart recorder or computer system with an
Analog to Digital Converter card. If you go the digital way I have a 12 or
16 bit A/D card available (see http://psn.quake.net/atod.html). Many PSN
stations are now using it along with my data logging software SDR. SDR
records the data from your sensor and produces PSN formatted event files
that can then be displayed and analyzed with my WinQuake program.
If you need anymore info please contact me.
Regards,
Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: new station
Date: Mon, 16 Jun 1997 23:02:09 +1200
greetings all,
we have a new member added to the map and listing of
PSN stations
Please extend a warm welcome to Giovanni Rotta of Italy. This is the
second Itilian station.
Dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Robert L. Thomasson" <102073.3346@..............>
Subject: Seismograph Construction
Date: 16 Jun 97 15:38:08 EDT
Greetings,
I sat down at the computer Sunday morning and started reading through all the
psn mailing list archives. It was almost dark when I finally went outside for
a break. Thanks for a very educational and entertaining day.
Based on what I read, I've decided to start building a basic Lehman seismograph
system. I considered a Shackleford-Gundersen because I'm intrigued by the
electronics, but I'm also intimidated by the seeming complexity. At this stage
I'm confident I can get a Lehman working fairly soon, and would rather have
something that works reasonably well right away, than have a superior device
that I finally get to work next year sometime. Once the Lehman is up and
running, and I'm a little smarter, I'll start the S-G.
I read where several builders successfully use an S-G sensor system on a Lehman
boom. I considered building a vertical hanging pendulum using a Lehman type
coil and magnet sensor, since I liked the traditional vertical pendulum and the
fact that it used less floor space. Am I right in concluding that in order to
get a vertical pendulum device with a period equal to a Lehman horizontal boom,
I'd probably have to put the top of the vertical pendulum support through the
roof?
I plan on using cow magnets for the sensor and for damping, since I have
several of them already, and it will help compensate for the $100+ I spent on
ADXL05 sensors I probably won't be using. Scientific American got me
interested in seismology in the first place, so I don't have too many hard
feelings about the misleading article. I don't want to use oil damping unless
I have to, mainly because I already have a garage full of oily motorcycle parts
and I would like to build something that doesn't use oil for a change. Besides,
magnetic damping seems a lot more interesting although I think the oil damping
is more easily adjustable, since you can vary oil level, viscosity and size of
the paddle.
I have a piece of broken kitchen countertop made of some kind of heavy
Corian-like substance that will get used for the base. I have a collection of
broken aluminum hang glider parts that may serve as the boom and support
structure. I haven't figured out the details yet, but I'll be using a lot of
ideas from this forum. I think I also have relay coils on hand, so I might be
able to get this going relatively cheap. With all the money I'm saving I'm
buying a geophone for vertical strong motion detection. I haven't yet decided
what to do for A/D conversion, probably buy one of Larry Cochrane's systems.
For a newcomer, it is really great to have all the acquisition and display
software available. I know how much work and time is involved in developing it.
I do have some questions regardng EMON and SDR. I'm not very computer
literate, so please bear with me if I'm out in left field here and am missing
some fundamental facts. I understand that the recording software runs on DOS
and that the display software (Winquake) runs on Windows; it's necessary to
transfer data from a computer running DOS to one running windows in order to
display it. As I think I understand it, the reason is that running straight
DOS format is much faster for data recording and accesses memory directly rather
than through a two stage process using Windows. Is this extra speed still
significant with the recent faster Pentium processors? What about Windows NT?
Doesn't it operate in real mode without DOS? Also, it seems to me that the
necessary sampling rate for seismic events is fairly slow and that a real time
Windows based acquisition and display program would work fine. I hope it
doesn't sound like I'm second guessing anyone; I'm not smart enough to be doing
that. These are just questions from a novice based on very limited knowledge and
experience. I just don't want to accept that I'll either have to use two
computers or transfer files to a disc before I can plot results.
Thanks to everyone who has contributed to this list.
Bob
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.......>
Subject: Re: Seismograph Construction
Date: Mon, 16 Jun 1997 14:42:46 -0700
Bob --
Glad to hear you are about to undertake construction of a seismometer. You
are correct that freely hanging pendulum would have to be very tall to
match the period of a relatively compact Lehman. Just in case you were
thinking of hanging it from your second-story rafters, I think that
wind-induced movement in any building short of Boulder Dam would add too
much noise.
Although you didn't ask, I have a comment about your base plate. If you
are planning to build a Lehman design, it is rather sensitive to tilt of
the baseplate when adjusted for a fairly long period. My concern is that
small, temperature-induced warping of a plastic baseplate would cause the
thing to lean over enough to be against the stop. Perhaps someone that has
more experience with plastic bases could comment, but I'd recommend metal
-- perhaps aluminum.
Karl Cunningham
La Mesa, CA.
karlc@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jean-Yves Trudel <jtrudel@.........>
Subject: Richter&Mercalli
Date: Mon, 16 Jun 1997 17:49:06 -0700
Hi Dave !
Thank you very much for the information about the original Richter
magnitude scale and the Mercalli Scale.
I'm a newcomer on the list, and right now I have lots of reading to do
concerning the seismic wave information that I have from you and our
group. I found many documents with the address proposed.
I was really confused.
Again thank you very much !
Jean-Yves
_____________________________________________________________________
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From: "Robert L. Thomasson" <102073.3346@..............>
Subject: Re: Seismograph Construction
Date: 16 Jun 97 19:12:23 EDT
<<My concern is that
small, temperature-induced warping of a plastic baseplate would cause the
thing to lean over enough to be against the stop. Perhaps someone that has
more experience with plastic bases could comment, but I'd recommend metal
-- perhaps aluminum.>>
Karl,
You're probably right. I don't know anything about this plastic material I
have, except it's about 25 mm thick and is real heavy. There's a great salvage
yard here in Reno where I can get a piece of aluminum.
Thanks, Bob
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: standards?
Date: Mon, 16 Jun 1997 17:25:12 -0600
John-
I have included comments in the text of your questions second below:
John Hernlund wrote:
>
> > John-
> > Local magnitude (ML) is proportional to the peak pendulum displacement,
> > not the peak ground displacement, i.e., without correction for the
> > complex response of a damped harmonic oscillator, the Wood-Anderson
> > seismograph with a 0.8 s natural period.
>
> Okay, so is there a standard seismograph somewhere that everyone in the
> world calibrates their seismograph with? This seems very strange to me.
There has recently been a shift to use moment magnitude, Mw, which is
based on the seismic moment of an earthquake. The moment is calculated
from the integral of the displacement ground motion and the elastic
properties of the Earth rather than from the peak amplitude on an
standard seismograph.
> How difficult would it be to find the energy released in Joules and the
> particle motion everywhere around the focus knowing the elastic properties
> of the rocks/material and having a good approximation of ground
> displacement as a function of time at the epicenter?
Given the magnitude and depth of an earthquake, one can then estimate
the moment and predict the ground motions produced anywhere on the focal
sphere of an idealized Earth. However, because of the heterogeniety of
the near-surface of the Earth and consequent variation of the elastic
properties, it is common for ground motions to locally vary by a factor
of two or more.
-Edward
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.......>
Subject: Data Exchange
Date: Mon, 16 Jun 1997 17:48:06 -0700
Hi all --
There is something I've been wondering about. Please tell me where I'm off
base.
It seems that PSN seismic information is usually exchanged as velocity
data, probably because this is what comes out of a magnet-in-a-coil
detector arrangement. I get the impression that in the past, much of the
data exchange between professionals in this field was also as velocity,
probably for the same reason. I understand too, that changing between
acceleration, velocity, and displacement is fairly simple calculus, and
handled easily today by most home computers.
It seems that another reason that data has been exchanged (and probably
detected) as velocity is this: The characteristics of the earth and
mechanisms that generate earthquakes are such that, for a given event, the
amplitude of the signal as a function of frequency covers the smallest
dynamic range when it is expressed as velocity. This means that much of
the entire envelope of signals from a given event will be within the range
of simple amplifiers and A/D convertors, if it is velocity data.
Conversely, acceleration and displacement data will require wider dynamic
range, if one wants to convey very much of the information captured from a
given event.
But, I get the impression that with the advent of force-balance
seismometers with acceleration outputs and the development of
very-wide-dynamic-range A/D convertors, this is changing in the direction
of using acceleration data, at least in the professional arena. Am I on
the right track, or do I have a misconception here?
I seems that if you have a force-balance seismometer with an acceleration
output (analog), you stand the best change of capturing the data with
minimum noise and distortion if you digitize right at the analog output,
rather than converting it to velocity with more analog circuitry. This is,
however, provided you have an A/D that is good enough. This requires an
A/D with very good SNR, but these are getting *much* better, and at
incredibly inexpensive prices.
I'm sort of rambling, but my point is this: Should we, as amateurs, be
leaning in the same direction? I'm certain the trend to higher capability
electronic components for less money will continue unabated, and I think
the time is near when amateurs will be able to achieve 24-bit dynamic
range, or something close to it. I'd like to hear comments, if anyone
cares to.
Thanks,
Karl Cunningham
La Mesa, CA.
karlc@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: barry lotz <"gbl@......."@.......>
Subject: Re: Seismograph Construction
Date: Mon, 16 Jun 1997 17:28:34 -0700
Hi
"More input":
I tend to build using truss type construction(triangles). My Lehman main
frame is made of copper water water pipe mitered and soldered at the
ends. My boom is a truss made of brazing rod. Both light and stiff. BTW
you mentioned about damping, Putting a resistor across the coil will
provide energy disipation. You'll have to use a trim pot to get the
degree you want. Works for me.
Barry
Robert L. Thomasson wrote:
>
> <<My concern is that
> small, temperature-induced warping of a plastic baseplate would cause the
> thing to lean over enough to be against the stop. Perhaps someone that has
> more experience with plastic bases could comment, but I'd recommend metal
> -- perhaps aluminum.>>
>
> Karl,
>
> You're probably right. I don't know anything about this plastic material I
> have, except it's about 25 mm thick and is real heavy. There's a great salvage
> yard here in Reno where I can get a piece of aluminum.
>
> Thanks, Bob
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: barry lotz <"gbl@......."@.......>
Subject: Re: Data Exchange
Date: Mon, 16 Jun 1997 18:05:53 -0700
Hi Karl
This has has been generating a lot of thought and frustration for me
recently. I have been measuring velocity successfully for years but
would like to use my force balance sensor more for stability and size
reasons. What is stopping me is that I have noticed with records I have
seen that acceleration tends to be composed of higher frequencies. There
may be more environmental noise in the acceleration record than the
velocity band. Filtering the wanted amplitude from unwanted amplitude at
a given frequency is what I'm wrestling with right now. How does one
separate a 2 hz event component from a 2 hz background noise? You can't
just chop it out completely. Where I live my highest velocity frequency
is around 5-7 hz. With acceleration its somewhare from 15-25 hz. I have
been working with long term/short term averaging processes and also
performing FFTs on the background noise just before an event to try to
eliminate some of the unwanted signal from the actual event . I have had
limited success to date. I have heard also that acceleration
measurements tend to be also smaller than velocity so more amplification
would be required. Environmental noise is what limits my gain from being
higher, not the concern of clipping a record. I have gone reading two
channels of 12 bit data at different gains as opposed to a higher A/D
resolution. I keep the channel that doesn't clip.
I agree with you that one should convert to digital as soon as
possible. Both digital data and math/numbers are noise immune (digital
filters as an example). I guess that's it for my ramble.
Barry
Karl Cunningham wrote:
>
> Hi all --
>
> There is something I've been wondering about. Please tell me where I'm off
> base.
>
> It seems that PSN seismic information is usually exchanged as velocity
> data, probably because this is what comes out of a magnet-in-a-coil
> detector arrangement. I get the impression that in the past, much of the
> data exchange between professionals in this field was also as velocity,
> probably for the same reason. I understand too, that changing between
> acceleration, velocity, and displacement is fairly simple calculus, and
> handled easily today by most home computers.
>
> It seems that another reason that data has been exchanged (and probably
> detected) as velocity is this: The characteristics of the earth and
> mechanisms that generate earthquakes are such that, for a given event, the
> amplitude of the signal as a function of frequency covers the smallest
> dynamic range when it is expressed as velocity. This means that much of
> the entire envelope of signals from a given event will be within the range
> of simple amplifiers and A/D convertors, if it is velocity data.
> Conversely, acceleration and displacement data will require wider dynamic
> range, if one wants to convey very much of the information captured from a
> given event.
>
> But, I get the impression that with the advent of force-balance
> seismometers with acceleration outputs and the development of
> very-wide-dynamic-range A/D convertors, this is changing in the direction
> of using acceleration data, at least in the professional arena. Am I on
> the right track, or do I have a misconception here?
>
> I seems that if you have a force-balance seismometer with an acceleration
> output (analog), you stand the best change of capturing the data with
> minimum noise and distortion if you digitize right at the analog output,
> rather than converting it to velocity with more analog circuitry. This is,
> however, provided you have an A/D that is good enough. This requires an
> A/D with very good SNR, but these are getting *much* better, and at
> incredibly inexpensive prices.
>
> I'm sort of rambling, but my point is this: Should we, as amateurs, be
> leaning in the same direction? I'm certain the trend to higher capability
> electronic components for less money will continue unabated, and I think
> the time is near when amateurs will be able to achieve 24-bit dynamic
> range, or something close to it. I'd like to hear comments, if anyone
> cares to.
>
> Thanks,
>
> Karl Cunningham
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.......>
Subject: Re: Data Exchange
Date: Mon, 16 Jun 1997 19:36:22 -0700
Barry --
WRT your high-frequency noise, I had the same problem with my FB sensor. I
took the approach of integrating the output with analog circuitry, which is
partly why I brought the subject up. It introduces a noticeable amount of
noise. But I do get a velocity output so I can compare/exchange with
everyone else, and the required dynamic range is less. The integrator is
nothing more than a first-order low-pass filter. I also have three more
poles of low-pass filtering at about 5Hz.
I don't thing there is a way (even theoretically) to filter out 2Hz noise
from 2Hz signal, unless you either know something more about the noise or
about the signal.
This thought just came to me:
If you take displacement data and differentiate it, you get velocity.
That's the same thing as putting emphasis on the low-frequency end at a
first-order rate (inversely proportional to frequency). Differentiating
again gives acceleration, which compared to displacement has emphasis at
the low end at a second-order rate (inversely proportional to the square of
the frequency). Perhaps there is another power (say 1.5 or .75 or
something) that could be used instead of 1 and 2 that I just mentioned,
that would be more suited for viewing seismic data and would do a better
job of ignoring the unwanted noise. I don't think there is an easy way to
do this with analog circuitry, but I'm sure it's not bad in the digital
domain. I'm sure it's been done before too.
Karl Cunningham
La Mesa, CA.
karlc@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ACole65464@.......
Subject: Why The Name "Jug"
Date: Mon, 16 Jun 1997 22:46:24 -0400 (EDT)
To Edward Cranswick,
You recently used the word "jug", and I have seen it used by other people
when referring to a velocity transducer. Can you, or someone else in this
group, tell me how they came up with the word "jug" for this type of an
instrument?
Thank you,
Allan Coleman
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Robert L. Thomasson" <102073.3346@..............>
Subject: Re: Seismograph Construction
Date: 16 Jun 97 23:51:32 EDT
Barry,
Thanks for the tip about adding a resistor across the coil to provide energy
disipation for damping. I would probably have figured that out eventually, but
you saved me some time. I also favor triangulated structures. This is really a
lot of fun designing the mechanical part of this thing - I can't wait til I
learn enough about electronics to start messing with the circuits, but right now
I have to pretty much copy what someone else has done.
Barry Lotz wrote <<I tend to build using truss type construction(triangles). My
Lehman main frame is made of copper water water pipe mitered and soldered at the
ends. My boom is a truss made of brazing rod. Both light and stiff. BTW
you mentioned about damping, Putting a resistor across the coil will
provide energy disipation. You'll have to use a trim pot to get the
degree you want. Works for me. >>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: tblank@.......... (Ted Blank)
Subject: Re: Seismograph Construction
Date: Mon, 16 Jun 1997 21:47:21 -0700 (PDT)
I think EMON should work in a DOS window on a Windows system, although I
have not tested this with real hardware (i.e. an A/D converter. This
would let you capture and display the data on the same system.
Of course you could always use QUAKEVU if you want the latest in
high-tech display and analysis tools. :-) This would also let you capture
and display on the same system... Just kidding. Even I use WinQuake
now, have for years.
Ted
>
> Greetings,
>
> I sat down at the computer Sunday morning and started reading through all the
> psn mailing list archives. It was almost dark when I finally went outside for
> a break. Thanks for a very educational and entertaining day.
>
> Based on what I read, I've decided to start building a basic Lehman seismograph
> system. I considered a Shackleford-Gundersen because I'm intrigued by the
> electronics, but I'm also intimidated by the seeming complexity. At this stage
> I'm confident I can get a Lehman working fairly soon, and would rather have
> something that works reasonably well right away, than have a superior device
> that I finally get to work next year sometime. Once the Lehman is up and
> running, and I'm a little smarter, I'll start the S-G.
>
> I read where several builders successfully use an S-G sensor system on a Lehman
> boom. I considered building a vertical hanging pendulum using a Lehman type
> coil and magnet sensor, since I liked the traditional vertical pendulum and the
> fact that it used less floor space. Am I right in concluding that in order to
> get a vertical pendulum device with a period equal to a Lehman horizontal boom,
> I'd probably have to put the top of the vertical pendulum support through the
> roof?
>
> I plan on using cow magnets for the sensor and for damping, since I have
> several of them already, and it will help compensate for the $100+ I spent on
> ADXL05 sensors I probably won't be using. Scientific American got me
> interested in seismology in the first place, so I don't have too many hard
> feelings about the misleading article. I don't want to use oil damping unless
> I have to, mainly because I already have a garage full of oily motorcycle parts
> and I would like to build something that doesn't use oil for a change. Besides,
> magnetic damping seems a lot more interesting although I think the oil damping
> is more easily adjustable, since you can vary oil level, viscosity and size of
> the paddle.
>
> I have a piece of broken kitchen countertop made of some kind of heavy
> Corian-like substance that will get used for the base. I have a collection of
> broken aluminum hang glider parts that may serve as the boom and support
> structure. I haven't figured out the details yet, but I'll be using a lot of
> ideas from this forum. I think I also have relay coils on hand, so I might be
> able to get this going relatively cheap. With all the money I'm saving I'm
> buying a geophone for vertical strong motion detection. I haven't yet decided
> what to do for A/D conversion, probably buy one of Larry Cochrane's systems.
>
> For a newcomer, it is really great to have all the acquisition and display
> software available. I know how much work and time is involved in developing it.
> I do have some questions regardng EMON and SDR. I'm not very computer
> literate, so please bear with me if I'm out in left field here and am missing
> some fundamental facts. I understand that the recording software runs on DOS
> and that the display software (Winquake) runs on Windows; it's necessary to
> transfer data from a computer running DOS to one running windows in order to
> display it. As I think I understand it, the reason is that running straight
> DOS format is much faster for data recording and accesses memory directly rather
> than through a two stage process using Windows. Is this extra speed still
> significant with the recent faster Pentium processors? What about Windows NT?
> Doesn't it operate in real mode without DOS? Also, it seems to me that the
> necessary sampling rate for seismic events is fairly slow and that a real time
> Windows based acquisition and display program would work fine. I hope it
> doesn't sound like I'm second guessing anyone; I'm not smart enough to be doing
> that. These are just questions from a novice based on very limited knowledge and
> experience. I just don't want to accept that I'll either have to use two
> computers or transfer files to a disc before I can plot results.
>
> Thanks to everyone who has contributed to this list.
>
> Bob
>
>
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Doug Crice <dcrice@............>
Subject: Re: Why The Name "Jug"
Date: Mon, 16 Jun 1997 23:09:41 -0700
ACole65464@....... wrote:
>
> To Edward Cranswick,
>
> You recently used the word "jug", and I have seen it used by other people
> when referring to a velocity transducer. Can you, or someone else in this
> group, tell me how they came up with the word "jug" for this type of an instrument?
>
Back circa the 1930's, the geophones used for petroleum exploration were
bigger, say the size of coffee cans, or "jugs". Seismic crews were
largely composed of "good ol boys" and "rednecks" who adopted slang
terms for the implements of their craft. They used the term "jugs" to
describe geophones. The people who located and retrieved the geophones
for the exploration geophysicist became known as "jug hustlers", later
reduced to the term "juggie". A juggie's job is demanding in many ways,
but intelligence is not a major factor, and "juggie" has become a term
to describe a person of limited intellectual talents. When a
geophysicist says he was working as a juggie, he means he was doing
menial labor.
I am a lttle better at exploration geophysics than earthquake
seismology.
Doug Crice
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert Avakian <ravakian@............>
Subject: Re: Why The Name "Jug"
Date: Tue, 17 Jun 1997 01:17:46 -0700
In the early days of exploration geophysics the geophones weighed about
20 lbs per and were shaped somewhat like a stoneware jug sans handle.
Hence "jug" = geophone. In the old days you grabbed two 20# jugs and
waded into the swamp. Today you garb 4 strings of ten 1# phones and
stride off into the same swamp. Ain't progress grand?
ACole65464@....... wrote:
>
> To Edward Cranswick,
>
> You recently used the word "jug", and I have seen it used by other people
> when referring to a velocity transducer. Can you, or someone else in this
> group, tell me how they came up with the word "jug" for this type of an
> instrument?
>
> Thank you,
>
> Allan Coleman
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Seismograph Construction
Date: Mon, 16 Jun 1997 22:55:51 -0700
At 03:38 PM 6/16/97 EDT, Robert L. Thomasson wrote:
>Greetings,
>Based on what I read, I've decided to start building a basic Lehman
seismograph
>system. I considered a Shackleford-Gundersen because I'm intrigued by the
>electronics, but I'm also intimidated by the seeming complexity. At this
stage
>I'm confident I can get a Lehman working fairly soon, and would rather have
>something that works reasonably well right away, than have a superior device
>that I finally get to work next year sometime. Once the Lehman is up and
>running, and I'm a little smarter, I'll start the S-G.
In a few weeks I should have a PC board available for the S-G sensor. The
layout is complete, all I need to do is go over it and see if everything is
OK. I think this will help some people who are not into breadboarding
electronic parts.
>
>I plan on using cow magnets for the sensor and for damping, since I have
>several of them already, and it will help compensate for the $100+ I spent on
>ADXL05 sensors I probably won't be using. Scientific American got me
>interested in seismology in the first place, so I don't have too many hard
>feelings about the misleading article. I don't want to use oil damping
unless
>I have to, mainly because I already have a garage full of oily motorcycle
parts
>and I would like to build something that doesn't use oil for a change.
Besides,
>magnetic damping seems a lot more interesting although I think the oil
damping
>is more easily adjustable, since you can vary oil level, viscosity and
size of
>the paddle.
I'm not sure if cow magnets are strong enough for dampening, depends on
your setup. I went back to oil dampening because of the interaction between
the magnet on the boom, that is used by the pickup coil, and the dampening
magnets. You can mount the pickup coil on the boom but then you may have
problems with the wire as it comes off of the boom.
>
>I have a piece of broken kitchen countertop made of some kind of heavy
>Corian-like substance that will get used for the base. I have a
collection of
>broken aluminum hang glider parts that may serve as the boom and support
>structure.
I would stay with aluminum for the baseplate as others have suggested.
>I haven't figured out the details yet, but I'll be using a lot of
>ideas from this forum. I think I also have relay coils on hand, so I
might be
>able to get this going relatively cheap.
A 220 vac relay works great. Much easier then winding one but you need to
use a horseshoe type magnet, not a cow magnet. Your local hardware store
may have a 22-30 lbs horseshoe magnet for around $20.00 that will allow the
coil to fit inside it. I adjust my Lehman so that the outer edge of the
coil is even with the front surface of the magnet. This way the boom can
move a little (a common problem with the Lehman) with out hitting the
magnet. If you can find a relay coil (maybe a 220 vac solenoid coil) that
has a large enough opening then the cow magnet may work.
>With all the money I'm saving I'm
>buying a geophone for vertical strong motion detection.
I don't think a geophone is considered, or can be used as, a strong motion
sensor. For a strong motion sensor you should be able to use the ADX05
chips. I currently have one channel running (*.lc6 file) using these chips.
>I haven't yet decided
>what to do for A/D conversion, probably buy one of Larry Cochrane's systems.
Great, thanks... The SMALL amount of money I make from the boards goes to
help pay for the equipment and electricity to keep this mailing list, my
web page and data archive going.
> For a newcomer, it is really great to have all the acquisition and display
>software available. I know how much work and time is involved in
developing it.
>I do have some questions regardng EMON and SDR. I'm not very computer
>literate, so please bear with me if I'm out in left field here and am missing
>some fundamental facts. I understand that the recording software runs on DOS
>and that the display software (Winquake) runs on Windows; it's necessary to
>transfer data from a computer running DOS to one running windows in order to
>display it.
To do it right you do need two systems. One for data logging and the other
for WinQuake and
other general computing stuff. IMHO you should have one system that only
does data logging. If you try to do it all on one system I think you will
have a lot of down time do to rebooting, software upgrades, general Windows
flakiness, etc... SDR will run on an old 33mhz 386/486 that are pretty
cheep now a days. To get around the transferring of event files you can
network your two systems together. This takes two network cards that cost
around $35. This way your event files will show up on your main computer
system. The problem is you need to keep both systems running for this to
work. To save $ you can share the monitor and keyboard by getting a switch
box that will let you switch between the two systems.
>As I think I understand it, the reason is that running straight
>DOS format is much faster for data recording and accesses memory directly
rather
>than through a two stage process using Windows. Is this extra speed still
>significant with the recent faster Pentium processors?
The problem with Windows (Win3.1 and 95, NT is a little better) is it is
not a very good real time processing environment. The problem is the
operation system can disable interrupts for long periods of time. For SDR
to keep accurate time it needs to keep up with a 1 millisecond (1000 hz or
about that same as a 9600 baud serial data stream), or 500us if you run it
with 6 channels at 100SPS, interrupt rate. This interrupt is generated by
the A/D card so that internal timing is independent of the PC's sometimes
terrible time keeping.
>What about Windows NT?
NT is what I use, it is a much better OS than the old Win3.1. Win95 is
somewhere between the old system and NT. The problem with NT is it's very
expensive and to handle hardware you need to write a special device driver.
Writings a device driver for NT, or other OS's, is not an easy task. Given
that my software is free (at this point) it's hard to justify spending 3-4
months of development time on a OS that cost over $250.
>Also, it seems to me that the
>necessary sampling rate for seismic events is fairly slow and that a real
time
>Windows based acquisition and display program would work fine.
Well that depends... If your are only recording one channel at 10 samples
per second (sps) your right. By if you want a system that can record
multiple channels at a constant rate of 50 to 100 sps you need a system
that can respond to a high data rate.
Hope this helps...
-Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Seismograph Construction
Date: Tue, 17 Jun 1997 01:00:57 -0700
At 09:47 PM 6/16/97 -0700, Ted Blank wrote:
>I think EMON should work in a DOS window on a Windows system, although I
>have not tested this with real hardware (i.e. an A/D converter. This
>would let you capture and display the data on the same system.
The problem with using EMON or SDR in a DOS box under Win3.1 or 95 is you
can't get a constant sample rate. Given that EMON poles the A/D card
(unlike SDR that uses an interrupt) for when the A/D chip is ready with new
data, if the operating system is off doing other things then it is not
gathering data during that time period. This loss of data can last for
100ths of milliseconds depending on your hardware and CPU speed. If EMON
(SDR has other problems do to loss of interrupts) had almost all of the CPU
power to keep a constant sample rate then the system would be so slow that
it would be almost worthless. You can not do direct hardware input and
output or interrupt handling under Windows NT so EMON or SDR will not work
in a DOS box under NT.
>
>Of course you could always use QUAKEVU if you want the latest in
>high-tech display and analysis tools. :-) This would also let you capture
>and display on the same system... Just kidding. Even I use WinQuake
>now, have for years.
When I first started writing WinQuake Ted was living in Japan. He was a
great help in getting it up and running. Do to the Internet we could
communicate daily, sometimes more then ones, which was a big help.
Regards,
Larry Cochrane
Redwood City, PSN
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: SW6079@.......
Subject: Re: Seismograph Construction
Date: Tue, 17 Jun 1997 09:12:49 -0400 (EDT)
On the seismograph construction.. I've used large dougnut magnets that were
scavenged from defunct microwave oven magnetrons. I got a whole bunch for a
dollar from a local repair shop. Good luck. Mike
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Robert L. Thomasson" <102073.3346@..............>
Subject: Seismograph Construction
Date: 17 Jun 97 10:41:49 EDT
Thanks to everyone for their input. My design keeps changing and improving due
to the feedback. I'll check in town for microwave oven magnets and compare
them to the hardware store horseshoe type. It seems that all the stuff I had
laying around for free is borderline or unsuitable, so I've got to go out and
spend some money. Oh well.
Larry, I didn't realize that you are supporting this mailing list out of your
own pocket. I've really gotten a lot of benefit from it. Thanks also for your
comments on the software. I'm learning, which is part of the fun. I have a
hunch that the Mac operating system would work in real time? Obviously, it
isn't worth developing software for, since there aren't enough of them around.
Catch 22.
The S-G board sounds very interesting. I'd like to build the coil/magnet system
first as partly a learning experience, and I'd like to experiment with it to
learn the fundamentals before I get in too far over my head. Also, I'm an
incorrigible hobbyist and would probably file my own transistors out of grains
of sand if my eyes were still up to it. Once the Lehman is running I'll
probably get your S-G board.
Every couple of years or so, we seem to get a 3 or 3.5 quake here locally
(Reno-Carson City area). From what I understand, this will send a Lehman or
S-G system off scale. I thought that a geo-phone (I probably used the term
"strong motion sensor" incorrectly) would work at this magnitude, but
evidently not?
Hope that someday I'll be contributing some ideas and comments of my own,
instead of just asking all these questions.
Thanks again, Bob
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: THE best book
Date: Tue, 17 Jun 1997 14:58:44 -0400
Hi gang,
I wanted to try Barnes & Noble home page just to see how it works. The=
URL is www.barnesandnoble.com
I asked it to search for Bolt, "Earthquakes and Geological Discovery" a=
nd
within a few seconds it said the price is $23.06, about $9 off the list
price.
The page worked well for this test and for everyone on this list, that
would be the best twenty three bucks you ever spent.
Bob Barns
_____________________________________________________________________
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From: David A Nelson <dann@........>
Subject: Mb 6.6 in the Aleutians
Date: Wed, 18 Jun 1997 11:20:00 +1200
did anyone record the Mb 6.6 in the Aleutian Is.
97/06/17 21:03:40 51.32N 179.35W 33.0 6.6Mb A ANDREANOF ISL, ALEUTIAN IS.
The helicorder at Univ. of Reno did record it.
dave
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Larry Cochrane <cochrane@..............>
Subject: Re: Mb 6.6 in the Aleutians
Date: Tue, 17 Jun 1997 15:27:32 -0700
Hi got a nice recording of it on my S-G sensor. I just sent it out to the
NewEvent mailing list.
-Larry
At 11:20 AM 6/18/97 +1200, you wrote:
>did anyone record the Mb 6.6 in the Aleutian Is.
>
>97/06/17 21:03:40 51.32N 179.35W 33.0 6.6Mb A ANDREANOF ISL, ALEUTIAN
IS.
>
> The helicorder at Univ. of Reno did record it.
>
> dave
> Dave A. Nelson
>
> 24 Jensen St.,
> Green Is., Dunedin,
> South Is.. New Zealand.
>
>http://psn.quake.net/dave/home.htm
>
>
>Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
>Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
> THE DIRECTION OF THE MOST DAMAGE
>Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Dennis Leatart <ASTROSEEK@.........>
Subject: Re: Mb 6.6 in the Aleutians
Date: Tue, 17 Jun 1997 18:01:48 -0700
I picked it up also David-- got a good trace!
--
_____ __
| \.-----.-----.-----.|__|.-----.
| -- | -__| | || ||__ --|
|_____/|_____|__|__|__|__||__||_____|
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Martin Brewer" <mbrewer@......>
Subject: Re: Mb 6.6 in the Aleutians
Date: Tue, 17 Jun 1997 21:56:23 -0300
----------
Hi Dave and Larry,
Bermuda picked up the Aleutian event and the Bermuda station is now
calibrated!! I shall send you copies of the SDR to your e-mail addresses.
I'm overwhelmed how well the sensor works. Thank you for all your help.
Regards,
Martin
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Martin Brewer" <mbrewer@......>
Subject: Re: Seismograph Construction
Date: Tue, 17 Jun 1997 22:37:07 -0300
Robert,
I have used a three foot by one foot sheet of half-inch Corian counter top
as a base for my Lehman. I stiffened the sides using aluminium sliding
glass door track. I found that the Corian still warped from side to side
so that there was a rest point for the boom on either side of the mid-line.
I corrected this by screwing a length of aluminium track across the base
immediately in front of the galvanized pipe support for the knife edge and
the boom wire.
Regards,
Martin
----------
> From: Robert L. Thomasson <102073.3346@..............>
> I have a piece of broken kitchen countertop made of some kind of heavy
> Corian-like substance that will get used for the base.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: barry lotz <"gbl@......."@.......>
Subject: Re: Mb 6.6 in the Aleutians
Date: Tue, 17 Jun 1997 19:59:53 -0700
Hi Dave
Yea I got it. Just need to edit a little.
Barry
PS - It's the first teleseismic event I have recorded with my new
triggering system.
>David A Nelson wrote:
>
> did anyone record the Mb 6.6 in the Aleutian Is.
>
> 97/06/17 21:03:40 51.32N 179.35W 33.0 6.6Mb A ANDREANOF ISL, ALEUTIAN IS.
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Data Exchange
Date: Tue, 17 Jun 1997 22:00:49 -0600
Karl-
Your statement below about velocity is a very astute observation. I
have been thinking about these matters for two decades, and I have never
heard the relationship between the dynamic range and the order of motion
-- acceleration, velocity, displacement -- of earthquake-generated
ground motions explained more succinctly.
The present "state of the art" seismic sensors are FBAs with 24-bit
A/Ds, and they are very HiTech and expensive: $5k to $50k. They are
"broad-band", 0.001 to 100.0 Hz, and all orders of motion can be derived
from their records. If they were mass-produced in lots of thousands
instead of lots of ten, they would be considerably cheaper and more
reliable.
So there is a trade-off between big bucks today and the patience to
wait for tomorrow ... or anyday there could be a paradigm shift, and
keeping track of ground motions in seismogenic regions will become as
common for the average resident as checking the air temperature on the
thermometer mounted outside the back door.
Thank you for the thought-provoking discussion.
-Edward
Karl Cunningham wrote:
>
> Hi all --
>
> There is something I've been wondering about. Please tell me where I'm off
> base.
>
> It seems that PSN seismic information is usually exchanged as velocity
> data, probably because this is what comes out of a magnet-in-a-coil
> detector arrangement. I get the impression that in the past, much of the
> data exchange between professionals in this field was also as velocity,
> probably for the same reason. I understand too, that changing between
> acceleration, velocity, and displacement is fairly simple calculus, and
> handled easily today by most home computers.
>
> It seems that another reason that data has been exchanged (and probably
> detected) as velocity is this: The characteristics of the earth and
> mechanisms that generate earthquakes are such that, for a given event, the
> amplitude of the signal as a function of frequency covers the smallest
> dynamic range when it is expressed as velocity. This means that much of
> the entire envelope of signals from a given event will be within the range
> of simple amplifiers and A/D convertors, if it is velocity data.
> Conversely, acceleration and displacement data will require wider dynamic
> range, if one wants to convey very much of the information captured from a
> given event.
>
> But, I get the impression that with the advent of force-balance
> seismometers with acceleration outputs and the development of
> very-wide-dynamic-range A/D convertors, this is changing in the direction
> of using acceleration data, at least in the professional arena. Am I on
> the right track, or do I have a misconception here?
>
> I seems that if you have a force-balance seismometer with an acceleration
> output (analog), you stand the best change of capturing the data with
> minimum noise and distortion if you digitize right at the analog output,
> rather than converting it to velocity with more analog circuitry. This is,
> however, provided you have an A/D that is good enough. This requires an
> A/D with very good SNR, but these are getting *much* better, and at
> incredibly inexpensive prices.
>
> I'm sort of rambling, but my point is this: Should we, as amateurs, be
> leaning in the same direction? I'm certain the trend to higher capability
> electronic components for less money will continue unabated, and I think
> the time is near when amateurs will be able to achieve 24-bit dynamic
> range, or something close to it. I'd like to hear comments, if anyone
> cares to.
>
> Thanks,
>
> Karl Cunningham
> La Mesa, CA.
> karlc@.......
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
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From: David A Nelson <dann@........>
Subject: Re: Mb 6.6 in the Aleutians
Date: Wed, 18 Jun 1997 16:04:22 +1200
barry,
well done looking forward to seeing it. just in the
middle of replying to martin in Bermuda he recorded it and sent me a copy
of the file for winquake.
just explaining to him to edit the file a bit to make it a bit smaller
for e-mailling it was 480 kb long took for ever to down load the
file covered 1 hr 21 mins of recording time.
cheers dave
At 07:59 PM 6/17/97 -0700, you wrote:
>Hi Dave
> Yea I got it. Just need to edit a little.
> Barry
>
>PS - It's the first teleseismic event I have recorded with my new
>triggering system.
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Data Exchange
Date: Tue, 17 Jun 1997 22:15:20 -0600
Barry-
To extract the seismic signal from the noisy acceleration trace, try
integrating the acceleration to velocity using WinQuake Version 2.4.
The noise, with random phase, will tend to cancel itself out, and the
seismic signal will be reinforced. Simple filtering with the FFT is
very effective in many cases, but it does not take advantage of the
different phase characteristics of signal and noise. Good luck! Tell
us if you obtain a satisfying result.
-Edward
PS. The good seismic picker or trigger algorithm in noisy data is one of
the Holy Grails of seismological instrumentation and processing.
barry lotz wrote:
>
> Hi Karl
> This has has been generating a lot of thought and frustration for me
> recently. I have been measuring velocity successfully for years but
> would like to use my force balance sensor more for stability and size
> reasons. What is stopping me is that I have noticed with records I have
> seen that acceleration tends to be composed of higher frequencies. There
> may be more environmental noise in the acceleration record than the
> velocity band. Filtering the wanted amplitude from unwanted amplitude at
> a given frequency is what I'm wrestling with right now. How does one
> separate a 2 hz event component from a 2 hz background noise? You can't
> just chop it out completely. Where I live my highest velocity frequency
> is around 5-7 hz. With acceleration its somewhare from 15-25 hz. I have
> been working with long term/short term averaging processes and also
> performing FFTs on the background noise just before an event to try to
> eliminate some of the unwanted signal from the actual event . I have had
> limited success to date. I have heard also that acceleration
> measurements tend to be also smaller than velocity so more amplification
> would be required. Environmental noise is what limits my gain from being
> higher, not the concern of clipping a record. I have gone reading two
> channels of 12 bit data at different gains as opposed to a higher A/D
> resolution. I keep the channel that doesn't clip.
> I agree with you that one should convert to digital as soon as
> possible. Both digital data and math/numbers are noise immune (digital
> filters as an example). I guess that's it for my ramble.
> Barry
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
1711 Illinois St cranswick@........
Golden, CO 80401 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
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From: "Robert L. Thomasson" <102073.3346@..............>
Subject: Re: Seismograph Construction
Date: 18 Jun 97 00:23:41 EDT
Barry Lotz wrote that his Lehman boom is a rigid triangulated structure made out
of brazing rod. Barry, did you do away with the piano wire and make a complete
rigid boom assembly, or is your boom still supported by wire? I'm heading
toward a light and rigid triangulated boom without wire support. I haven't
thought it all the way through yet, but I'll post a description when I'm ready
to go with it. I have some half baked ideas that I need to test first. I'm
really enjoying the design and learning phase of this project, but it's getting
time to fish or cut bait. Wish I could get this interested and enthusiastic
about making money. Congratulations on picking up the Aleutian quake. I
can't wait to get something up and running.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: barry lotz <"gbl@......."@.......>
Subject: Re: Seismograph Construction
Date: Tue, 17 Jun 1997 22:08:33 -0700
Hi Robert
I made the boom without the wire. The boom is about 8" tall at the
support and tapers down to about 3" at the coil. I have knife edges at
the top and bottom pointing in opposite directions to balance the force
couple of the boom weight. The coil vertical positioning is a little
touchy.
BTW - someone wrote a while back about having a motorized leveling
screw for their Lehman. I think this would help the drifting/tilting of
this type of sensor. One could attach a low power small DC motor to the
fixed base (so it wouldn't vibrate the sensor as much) and gear it down
.. For the feedback one could use two optical emitter/detector circuits.
when the boom end moved so far one way it would block or not the optical
beam causing the motor to rotate in the appropriate direction. There
would have to be some hysteresis to keep the hunting down.
Barry
Robert L. Thomasson wrote:
>
> Barry Lotz wrote that his Lehman boom is a rigid triangulated structure made out
> of brazing rod. Barry, did you do away with the piano wire and make a complete
> rigid boom assembly, or is your boom still supported by wire? I'm heading
> toward a light and rigid triangulated boom without wire support. I haven't
> thought it all the way through yet, but I'll post a description when I'm ready
> to go with it. I have some half baked ideas that I need to test first. I'm
> really enjoying the design and learning phase of this project, but it's getting
> time to fish or cut bait. Wish I could get this interested and enthusiastic
> about making money. Congratulations on picking up the Aleutian quake. I
> can't wait to get something up and running.
>
_____________________________________________________________________
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From: "Martin Brewer" <mbrewer@......>
Subject: Atlantic 'quake?
Date: Wed, 18 Jun 1997 19:34:46 -0300
Hi everyone,
Did anyone else record a small - M4.9 - event about 2,200 km from Bermuda
with an origin time of around 21:35 UTC on 18 June 1997
Regards,
Martin
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From: "John Hernlund" <69277@..................>
Subject: ????
Date: Wed, 18 Jun 1997 22:36:02 -0700 (MST)
> There has recently been a shift to use moment magnitude, Mw, which is
> based on the seismic moment of an earthquake. The moment is calculated
> from the integral of the displacement ground motion and the elastic
> properties of the Earth rather than from the peak amplitude on an
> standard seismograph.
Could anyone direct me to a book on how these moments are calculated?
This sounds fascinating! Is the function clean so that you could post it
here?
> Given the magnitude and depth of an earthquake, one can then estimate
> the moment and predict the ground motions produced anywhere on the focal
> sphere of an idealized Earth. However, because of the heterogeniety of
> the near-surface of the Earth and consequent variation of the elastic
> properties, it is common for ground motions to locally vary by a factor
> of two or more.
Okay, I can definitely see that. I have heard that sediment laden
areas especially are a lot more susceptible to higher displacements and
internal reflections, in addition to liquifaction.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "John Hernlund" <69277@..................>
Subject: velocity
Date: Wed, 18 Jun 1997 22:44:01 -0700 (MST)
>
> It seems that PSN seismic information is usually exchanged as velocity
> data, probably because this is what comes out of a magnet-in-a-coil
> detector arrangement. I get the impression that in the past, much of the
> data exchange between professionals in this field was also as velocity,
> probably for the same reason. I understand too, that changing between
> acceleration, velocity, and displacement is fairly simple calculus, and
> handled easily today by most home computers.
Yeah, it seems likely that this is so because the voltage produced in
the coil arrangement is proportional to the velocity. For simple A/D
conversion it makes sense to use this kind of data. Plus, this makes it a
whole lot easier to plot the acceleration and displacement as they are one
derivative removed from the data. If, on the other hand, you use
acceleration data the displacement is two derivatives away, each step
adding a lot more chance for error and inaccuracy...
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Public Seismic Network Mailing List (PSN-L)
From: "Robert L. Thomasson" <102073.3346@..............>
Subject: Displacement Sensor
Date: 19 Jun 97 02:28:37 EDT
Has anyone had any experience using a commercial proximity probe eddy current
sensor in a seismograph? The ones used for industrial machinery vibration
monitoring seem like they'd work. They would work at extremely low frequencies
since they are measuring displacement, and I believe they will work well past
the highest frequencies we're interested in. They send a voltage signal
proportional to the distance from a conductor (greater distance, greater
voltage). They cost about $300 new, with the necessary black box driver, but
they should be available used/surplus for a lot less.
A potential problem might be motion that is past the range of the sensor, which
seems to be about 0.1" for the most common eddy current probes. This could
possibly be overcome by mounting the probe vertically underneath a Lehman boom
with an inclined plane shaped conductor fastened to the bottom of it so that a
horizontal motion of 3X or so of the boom would only result in an increase in
vertical distance between the probe and the inclined surface of 1X. ( A picture
would be worth a lot right now, but I've never tried keyboard artwork). There
would of course be a corresponding loss in sensitivity. I don't know if
commercial eddy current probes are commonly used for seismographs or unsuitable
for some good reason, but the only way to find out is to ask. Any comments?
Thanks, Bob
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Robert L Barns <75612.2635@..............>
Subject: Bermuda 'quake
Date: Fri, 20 Jun 1997 11:11:11 -0400
Martin Brewer,
Re:your quake, a 4.9 at about 21:35 on 6/18. My map sez Bermuda is ~32=
N
and 65W. This is 830 miles from me. A prog. I use to calc. relative
signal strength here sez that I should have seen it far above my noise
level. I saw nothing even though the Lehman was working well.
I got a good 'gram from the SE Pacific Rise, 6/10, 21:53:45, m6.1 which=
had a rel. sig. only 1/3 of that for your event.
Bob Barns
Berkeley Heights, NJ USA
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Dennis Leatart <ASTROSEEK@.........>
Subject: SOUTHERN CALIFORNIA QUAKES (NEAR CATALINA) P.O.
Date: Fri, 20 Jun 1997 10:12:26 -0700
Did anyone else pick up the series of quakes off southern California?
The main quake measured 4.5 but appears larger on my gram -- the others
were 4.1 and 4.3. I was about 152 km from these. We felt the 1st one.
--
_____ __
| \.-----.-----.-----.|__|.-----.
| -- | -__| | || ||__ --|
|_____/|_____|__|__|__|__||__||_____|
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: mbruenje@........ (Fred Bruenjes)
Subject: Re: SOUTHERN CALIFORNIA QUAKES (NEAR CATALINA) P.O.
Date: Fri, 20 Jun 1997 11:32:05 -0700
>Did anyone else pick up the series of quakes off southern California?
I sure did, here in San Diego, where I am only about 100km from the
epicenters. I didn't feel the first one, but I did feel the third one - a
4.3. It was a very weak rolling motion that lasted a few seconds. I could
also hear some of the stuff on my shelves rattling.
I have an ADXL05 running now, and it didn't pick up anything. That
surprises me, as I would have expected it to pick up quakes that are this
close and this big.
I've posted four of the quake traces from my Lehman on my web page at:
http://icse1.ucsd.edu/~mbruenje/seismo/
Fred
------------------------------------------
Fred Bruenjes mbruenje@........
http://icse1.ucsd.edu/~mbruenje/index.html
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Charles R. Patton" <patton@..........>
Subject: Re: Clamping diodes? (with revised information)
Date: Fri, 20 Jun 1997 11:52:40 -0700
I've tried to send this four times from home since last Saturday --
So I'm giving up and sending it from work. Maybe it will get through.
In any case, if previous posts come through eventually, I apologize
in advance.
-------
Clamping comes in steps -- the amount of effort/cost you want to
apply.
Level 1) As Roger pointed out the simple first step is to use signal
diodes, but they have about a 0.3 V limit before they can start to
interact with your desired signal -- i.e., they can be viewed as soft
clamps which start at about 0.4 V and are in the 10's of milliamps at
about 0.6V.
Level 2) Standard small zeners. They're available from a couple of
volts to hundreds of volts. The levels below about 6 V are softer and
more like the normal diode forward conduction. The problem with
zeners is their high junction capacitance. In the case of geophones,
this probably will not be a problem. One solution to that is to add
signal diodes in series. Then the capacitance becomes the signal
diode's capacitance. (So the group becomes two zeners back-to-back in
series with two diodes in parallel -- this combination doesn't break
down the signal diodes.) These methods typically good to some 10's
of milliamps and with some zeners maybe 100's of milliamps.
Level 3)
TVSD (transient voltage suppressor diodes). These are really back-
to-back zeners optimized for transient pulse current conditions.
General Instrument makes a lot these types. Usually the rating is in
joules (total heating they can adsorb. In transient conditions these
units can clamp amps to 10's of amps. In low voltage circuits, such as
IC and so forth, these can be the best, because they have the sharpest
'knee' -- see next item -- and lowest impedance)
MOV (metal-oxide varistors) These are amorphous ceramic semiconduc-
tor devices which have a slightly softer "knee" (the transition from
non-conducting to conducting) than zeners but are capable of larger
pulses. GE makes a lot of these. They are available from a few
volts to hundred's of volts operating potential. Companies like
McGraw-Edison make powerline versions of these to thousands of volts
of standoff capability and lightning strike adsorbtion capability.
Gas tubes (of which the neon is a poor variation for this applica-
tion) Preferably it's filled with additional gases (I believe its
Argon or Xenon that give better qualities) which give a very low
impedance when they fire. Gas tubes are good because of their low
capacitance in the non-conducting state. They are typically available
in voltages from about 100 to 300 in several steps in the small glass
envelop and can look just like a neon light, but they are much better.
Industrial versions are packaged in ceramic and can be sized for
lightning strikes. (They are very fast also.) Lumex Opto/Components
Inc. of Palatine, Illinois (http://www.lumex.com 1-847-359-2790)
makes various gas tube arresters. Even the small units will conduct
several amps, but their main drawback is the relatively high strike
voltage in comparison to the IC's you would like to protect.
Level 3.5)
Spark gaps. You can place minimum spacing conductors with air for
insulation (i.e., don't do a solder mask over this) when you lay out
your circuit board, i.e., 0.008 to 0.012 inches. This combination
will break down from about 700 to 1000 volts. Since virtually all
semiconductor ICs today have ESD specs from about 1500 to 2500 volts,
this can provide significant protection for essentially free. Be sure
the combination has a good path to earth ground and is stacked as
follows:
<------------------ signal high
v
gap
^
<------------------ logic ground
v
gap
^
<------------------earth ground
Reversing the logic ground and earth ground in the picture above leads
to overstress of the ICs in the event of an ESD hit.
The phone line to your house is typically protected with carbon
blocks spaced apart with a mica shim with a hole in it. This is a
spark gap with a vengeance. If enough energy is there -- such a
direct lightning hit -- the carbon blocks enter the arc regime and
short. Very good protection. Phone lines are often protected with
gas tubes also or the combination of both gas tubes and carbon blocks.
So that gives you a hint how to do high power protection from a re-
motely located sensor exposed to potential lightning strikes.
Additional techniques involve the use of fuses or resettable fuses
(such as the Raychem polyfuses) in series with lines between the over-
voltage source and the shunting clamps. So the clamps protect your
circuit. If the energy is enough to destroy the clamps, the fuses
open the circuit before that happens. I once had an application where
I used a pair of panel light bulbs, like #47s, in series with a dedi-
cated phone to protect the output data transmitter IC. (Actually I
didn't care about the IC per se, but I didn't want to take out the whole
card it was in. It worked like planned at least twice over some years
where lightning had apparently hit somewhere along the line. We were
some miles from the central office so there was a lot of exposure.
Anyway the bulbs and IC would blow, but that was it.
Hope this helps,
"Charles R. Patton, Editor, Geo-Monitor" <patton@.........>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Bermuda 'quake
Date: Sat, 21 Jun 1997 12:39:38 +1200
Yes Bob,
Martin and I came to the conclusion that it was probably
some local manmade noise
ther was no real P and S and the sig. was not consistant with a normal equake
Dave
At 11:11 AM 6/20/97 -0400, you wrote:
>Martin Brewer,
> Re:your quake, a 4.9 at about 21:35 on 6/18. My map sez Bermuda is ~32N
>and 65W. This is 830 miles from me. A prog. I use to calc. relative
>signal strength here sez that I should have seen it far above my noise
>level. I saw nothing even though the Lehman was working well.
> I got a good 'gram from the SE Pacific Rise, 6/10, 21:53:45, m6.1 which
>had a rel. sig. only 1/3 of that for your event.
>Bob Barns
>Berkeley Heights, NJ USA
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: SOUTHERN CALIFORNIA QUAKES (NEAR CATALINA) P.O.
Date: Sat, 21 Jun 1997 12:43:56 +1200
You probably reqalise now how insensitive they are,.....
I discovered during the week that the New Zealand seismological obs. have
been exp. with those chips in strong motion seismographs for recording
accelerations that exceed .75g .....
big shakes!! or not quite so big but right underneath you ones.
Dave
At 11:32 AM 6/20/97 -0700, you wrote:
>>I sure did, here in San Diego, where I am only about 100km from the
>epicenters. I didn't feel the first one, but I did feel the third one - a
>4.3. It was a very weak rolling motion that lasted a few seconds. I could
>also hear some of the stuff on my shelves rattling.
>
>I have an ADXL05 running now, and it didn't pick up anything. That
>surprises me, as I would have expected it to pick up quakes that are this
>close and this big.
>
>I've posted four of the quake traces from my Lehman on my web page at:
>
>http://icse1.ucsd.edu/~mbruenje/seismo/
>
>
>
>Fred
>
>
>
>------------------------------------------
>Fred Bruenjes mbruenje@........
>http://icse1.ucsd.edu/~mbruenje/index.html
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: barry lotz <"gbl@......."@.......>
Subject: Re: Clamping diodes? (with revised information)
Date: Fri, 20 Jun 1997 17:32:56 -0700
Charles
Most of the sensors that I use have gains greater than 10 so 0.3 v is
usually good for transients.
Barry
Charles R. Patton wrote:
> Clamping comes in steps -- the amount of effort/cost you want to
> apply.
> Level 1) As Roger pointed out the simple first step is to use signal
> diodes, but they have about a 0.3 V limit before they can start to
> interact with your desired signal -- i.e., they can be viewed as soft
> clamps which start at about 0.4 V and are in the 10's of milliamps at
> about 0.6V.
>
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: barry lotz <"gbl@......."@.......>
Subject: Re: SOUTHERN CALIFORNIA QUAKES (NEAR CATALINA) P.O.
Date: Fri, 20 Jun 1997 17:37:18 -0700
Dennis
I got the S and surface waves of the 4.5 event but missed the P. My
threshohold hadn't been reduced as yet from the noisy day.
Barry
PS I'm about 40 mi NE of Sacramento
>Dennis Leatart wrote:
>
> Did anyone else pick up the series of quakes off southern California?
> The main quake measured 4.5 but appears larger on my gram -- the others
> were 4.1 and 4.3. I was about 152 km from these. We felt the 1st one.
> --
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Lucas Haag <lhaag@..............>
Subject: Re: Geophones & PVC Pipe Project
Date: Fri, 20 Jun 97 22:40:38 CDT
I would like to see you plans if you wouldn't mind I would like to build
something very similar.
Thanks,
Lucas Haag
At 05:41 PM 6/13/97 -0400, you wrote:
>Thank you for that information on the geophones. I am in the process of
>designing a very small and cheap seismograph that fits into a peice of 8 inch
>PVC pipe. the geophone and the electronics package all fit inside the pipe
>and need to be buried. I was having trouble finding these geophones though
>and your info has made my first prototype possible. Thanks Again.
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
************************************************
Lucas Haag
HCR 66 Box 25A
Bartley, Nebraska 69020-9717
Email: lhaag@.............. OR haag_cnslt@...........
World Wide Web: http://www.swnebr.net/~lhaag
************************************************
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: Geophones & PVC Pipe Project
Date: Sat, 21 Jun 1997 16:45:59 +1200
Just my thoughts,
I started with preamps in the pipes as well but
found that they were too suseptable to temp. changes and moisture
ingressions through the sealer.
I found it a lot easier and convient to have only the geophones in the
plastic tube buried in the ground and have either coax or multi core
screened computer data cable back into the house to the preamps and data
logging gear.
BIG ADVANTAGE.... is that you can experiment with preamp modifications/
gain settings etc without disturbing the buried seismometers. You don't
have to wait for dry weather to dig up the units for repair etc.
Dave N.
At 10:40 PM 6/20/97 CDT, you wrote:
>I would like to see you plans if you wouldn't mind I would like to build
>something very similar.
>Thanks,
>Lucas Haag
>
>At 05:41 PM 6/13/97 -0400, you wrote:
>>Thank you for that information on the geophones. I am in the process of
>>designing a very small and cheap seismograph that fits into a peice of 8 inch
>>PVC pipe. the geophone and the electronics package all fit inside the pipe
>>and need to be buried. I was having trouble finding these geophones though
>>and your info has made my first prototype possible. Thanks Again.
>>
>>_____________________________________________________________________
>>
>>Public Seismic Network Mailing List (PSN-L)
>>
>>To leave this list email listserver@............. with the body of the
>>message: leave PSN-L
>>
>>
>************************************************
>Lucas Haag
>HCR 66 Box 25A
>Bartley, Nebraska 69020-9717
>Email: lhaag@.............. OR haag_cnslt@...........
>World Wide Web: http://www.swnebr.net/~lhaag
>************************************************
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: ????
Date: Sat, 21 Jun 1997 17:20:20 +1200
John H.,
an excellent text book to read is the the text for my
university geophysics papers that I did it is called The Solid Earth,
An Introduction to Global Geophysics. by C.M.R. Fowler
Some of it you may find a bit heady but it covers present day and past
plate motions and reconstructions; seismic wave propagation; magnitude
calculations M, Mb, Ms, Mo, Mw radioactive element decay for age
calculations; Triple junctions as in the Cape Mendocino T.Junction of
Nth Calif. coast.; Role of earth's magnetic field; reflection and
refraction seismology for study of the earth's interion and exploration;
Gravity, gravity of the Earth, Gravity Anomalies
and a whole mass of other stuff
as a sample for your question about Moment Magnitude Mw firstly the
seismic moment Mo has to be calc. Mo = u (mu) x A x u
u (mu) = shear modulus of the rock that the fault is in
A = the rupture area of the fault
u = the average displacement on the fault (caused by the quake)
The seismic moment can be determined by observations and estimates of the
fault-plane area and displacement. The seismic moment can also be expressed
in terms of the low-freq. amplitude spectra of surface waves. It does not
yield an accurate esitmate in the drop in stress for the quake.
Both the body wave and the surface wave magnitude scales saturate (do not
give large enough values) for very large earthquakes and are strongly
dependant on the freq. of the seismic wave. Therefore, to estimate the
size of big quakes, long period (low freq.) waves are used. A more
suitable magnitude scale called the moment magnitude Mw is obtained from the
seismic moment. The moment magnitude has been defined as:
Mw = 2/3 log10 Mo - 6.0
and has the important advantage over the other magnitude scales that it
does not saturate towards the top end of the scale
a few examples of some well known quakes
1906 San Fran. ..... Ms 8.3 Mw 7.9
1960 Chile ...... Ms 8.3 Mw 9.5
1964 Alaska ...... Ms8.4 Mw 9.2
Dave N.
> Could anyone direct me to a book on how these moments are calculated?
>This sounds fascinating! Is the function clean so that you could post it
>here?
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: "Marty " <Marty39@.............>
Subject: Re: Moment Magnitude
Date: Sat, 21 Jun 1997 08:48:39 -0700
The moment magnitude of a fault may be determined my using the rupture
area. This method is currently used by the USGS to calculate magnitude in
the preparation of seismic hazard maps.
area=length*width
M=4.07 + 0.98 log a (square km)
use 12 km as a default value for fault width
the length is the surface trace of the fault
Martin Cline, R.G.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Lucas Haag <lhaag@..............>
Subject: Re: Geophones - AMP Circut & Display (Larry C.)
Date: Sat, 21 Jun 97 18:30:50 CDT
I couldnt hook it up to the computer because it is very cost prohibitive but
if I had some schamitacs (misspell!) I could probaly build a curcit. I can
wire-wrap and solder some. But I dont know what I could use for display.
Thanks,
Lucas Haag
At 11:01 PM 6/15/97 -0700, you wrote:
>At 04:10 PM 6/13/97 CDT, Lucas Haag wrote:
>>Another Question:
>>How can you look at and/or record the waveform patterens.
>>Thanks,
>>Lucas Haag
>
>Besides the sensor you will need an amplifier/filter board and then some
>sort of display. This can be a chart recorder or computer system with an
>Analog to Digital Converter card. If you go the digital way I have a 12 or
>16 bit A/D card available (see http://psn.quake.net/atod.html). Many PSN
>stations are now using it along with my data logging software SDR. SDR
>records the data from your sensor and produces PSN formatted event files
>that can then be displayed and analyzed with my WinQuake program.
>
>If you need anymore info please contact me.
>
>Regards,
>Larry Cochrane
>Redwood City, PSN
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
************************************************
Lucas Haag
HCR 66 Box 25A
Bartley, Nebraska 69020-9717
Email: lhaag@.............. OR haag_cnslt@...........
World Wide Web: http://www.swnebr.net/~lhaag
************************************************
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Lucas Haag <lhaag@..............>
Subject: Re: Geophones & PVC Pipe Project
Date: Sat, 21 Jun 97 18:30:56 CDT
What did you use for amp circuits?
At 04:45 PM 6/21/97 +1200, you wrote:
>Just my thoughts,
> I started with preamps in the pipes as well but
>found that they were too suseptable to temp. changes and moisture
>ingressions through the sealer.
> I found it a lot easier and convient to have only the geophones in the
>plastic tube buried in the ground and have either coax or multi core
>screened computer data cable back into the house to the preamps and data
>logging gear.
>
> BIG ADVANTAGE.... is that you can experiment with preamp modifications/
>gain settings etc without disturbing the buried seismometers. You don't
>have to wait for dry weather to dig up the units for repair etc.
>
>
>
> Dave N.
>
>
>
>At 10:40 PM 6/20/97 CDT, you wrote:
>>I would like to see you plans if you wouldn't mind I would like to build
>>something very similar.
>>Thanks,
>>Lucas Haag
>>
>>At 05:41 PM 6/13/97 -0400, you wrote:
>>>Thank you for that information on the geophones. I am in the process of
>>>designing a very small and cheap seismograph that fits into a peice of 8 inch
>>>PVC pipe. the geophone and the electronics package all fit inside the pipe
>>>and need to be buried. I was having trouble finding these geophones though
>>>and your info has made my first prototype possible. Thanks Again.
>>>
>>>_____________________________________________________________________
>>>
>>>Public Seismic Network Mailing List (PSN-L)
>>>
>>>To leave this list email listserver@............. with the body of the
>>>message: leave PSN-L
>>>
>>>
>>************************************************
>>Lucas Haag
>>HCR 66 Box 25A
>>Bartley, Nebraska 69020-9717
>>Email: lhaag@.............. OR haag_cnslt@...........
>>World Wide Web: http://www.swnebr.net/~lhaag
>>************************************************
>>
>>
>>_____________________________________________________________________
>>
>>Public Seismic Network Mailing List (PSN-L)
>>
>>To leave this list email listserver@............. with the body of the
>>message: leave PSN-L
>>
>>
> Dave A. Nelson
>
> 24 Jensen St.,
> Green Is., Dunedin,
> South Is.. New Zealand.
>
>http://psn.quake.net/dave/home.htm
>
>
>Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
>Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
> THE DIRECTION OF THE MOST DAMAGE
>Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
>
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
************************************************
Lucas Haag
HCR 66 Box 25A
Bartley, Nebraska 69020-9717
Email: lhaag@.............. OR haag_cnslt@...........
World Wide Web: http://www.swnebr.net/~lhaag
************************************************
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: ????
Date: Sat, 21 Jun 1997 18:07:26 -0600
John-
The Brune expression for seismic moment is as follows:
M0(dyne-cm)= 4 * Pi * p * B**3 * R * [Level]
------------------------------
2 * [radiation constant]
where
p = density of rock (g/cm**3)
B = shear wave velocity (cm/s)
R = distance from source to receiver (cm)
Level = long period level of displacement spectrum (cm-s)
radiation constant = value between 0.0 and 1.0 that corrects
for the radiation pattern of the fault that is
often set to 0.6, the RMS average over the
focal sphere.
John Hernlund wrote:
>
> > There has recently been a shift to use moment magnitude, Mw, which is
> > based on the seismic moment of an earthquake. The moment is calculated
> > from the integral of the displacement ground motion and the elastic
> > properties of the Earth rather than from the peak amplitude on an
> > standard seismograph.
>
> Could anyone direct me to a book on how these moments are calculated?
> This sounds fascinating! Is the function clean so that you could post it
> here?
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
PO Box 25046, Federal Center cranswick@........
Denver, CO 80225-0046 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: Re: ????
Date: Sun, 22 Jun 1997 13:40:29 +1200
John H.,
an excellent text book to read is the the text for my
university geophysics papers that I did it is called The Solid Earth,
An Introduction to Global Geophysics. by C.M.R. Fowler
Some of it you may find a bit heady but it covers present day and past
plate motions and reconstructions; seismic wave propagation; magnitude
calculations M, Mb, Ms, Mo, Mw radioactive element decay for age
calculations; Triple junctions as in the Cape Mendocino T.Junction of
Nth Calif. coast.; Role of earth's magnetic field; reflection and
refraction seismology for study of the earth's interion and exploration;
Gravity, gravity of the Earth, Gravity Anomalies
and a whole mass of other stuff
as a sample for your question about Moment Magnitude Mw firstly the
seismic moment Mo has to be calc. Mo = u (mu) x A x u
u (mu) = shear modulus of the rock that the fault is in
A = the rupture area of the fault
u = the average displacement on the fault (caused by the quake)
The seismic moment can be determined by observations and estimates of the
fault-plane area and displacement. The seismic moment can also be expressed
in terms of the low-freq. amplitude spectra of surface waves. It does not
yield an accurate esitmate in the drop in stress for the quake.
Both the body wave and the surface wave magnitude scales saturate (do not
give large enough values) for very large earthquakes and are strongly
dependant on the freq. of the seismic wave. Therefore, to estimate the
size of big quakes, long period (low freq.) waves are used. A more
suitable magnitude scale called the moment magnitude Mw is obtained from the
seismic moment. The moment magnitude has been defined as:
Mw = 2/3 log10 Mo - 6.0
and has the important advantage over the other magnitude scales that it
does not saturate towards the top end of the scale
a few examples of some well known quakes
1906 San Fran. ..... Ms 8.3 Mw 7.9
1960 Chile ...... Ms 8.3 Mw 9.5
1964 Alaska ...... Ms8.4 Mw 9.2
Dave N.
> Could anyone direct me to a book on how these moments are calculated?
>This sounds fascinating! Is the function clean so that you could post it
>here?
>
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Seism0man@.......
Subject: Re: Geophones & PVC Pipe Project
Date: Sun, 22 Jun 1997 04:24:26 -0400 (EDT)
In my prototype I was using 741 op amps for both amps and the filter cicuit.
I also had trouble with temp and moisture. However that all changed when I
filled the entire thing with fiberglass resin and buried the thing 3 and a
half feet under ground. The moisture problem totally disapeared and at 3 and
a half feet on the north side of my house the temp problem was at a minimum.
I haven't had a chance to work on this project much since I switched
jobs(i.e. I don't have electrical engineers at my aid anymore) but the idea
burns in my mind regularly. I want to switch to a newer op amp system to see
if I can't, for the most part, eliminate any more electronic's noise. My
backround noise here in Santa Cruz CA is very dependent on trafic, wind, and
storms at sea. I live in the mountains (with 300 foot redwoods) next to the
ocean with a major road (with lots of pot-holes) 400 feet away. uhh!!! Not
the best place for a seismograph. My hope are to be able to build lots of
these things to sell to schools and private parties at a minimum cost (i.e.
apx $120.00 just above cost) and to have there sensors e-mail me so my
computer can mull over the data and email back the networked results-fast.
Michael
King
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Lucas Haag <lhaag@..............>
Subject: Re: Geophones & PVC Pipe Project
Date: Sun, 22 Jun 97 11:15:41 CDT
Do you have some scamitics I could use for the amp? Was you then running it
into a computer with a A/D Converter or some other method.
Thanks,
At 04:24 AM 6/22/97 -0400, you wrote:
>In my prototype I was using 741 op amps for both amps and the filter cicuit.
> I also had trouble with temp and moisture. However that all changed when I
>filled the entire thing with fiberglass resin and buried the thing 3 and a
>half feet under ground. The moisture problem totally disapeared and at 3 and
>a half feet on the north side of my house the temp problem was at a minimum.
>I haven't had a chance to work on this project much since I switched
>jobs(i.e. I don't have electrical engineers at my aid anymore) but the idea
>burns in my mind regularly. I want to switch to a newer op amp system to see
>if I can't, for the most part, eliminate any more electronic's noise. My
>backround noise here in Santa Cruz CA is very dependent on trafic, wind, and
>storms at sea. I live in the mountains (with 300 foot redwoods) next to the
>ocean with a major road (with lots of pot-holes) 400 feet away. uhh!!! Not
>the best place for a seismograph. My hope are to be able to build lots of
>these things to sell to schools and private parties at a minimum cost (i.e.
>apx $120.00 just above cost) and to have there sensors e-mail me so my
>computer can mull over the data and email back the networked results-fast.
>
>
>
>
>
>
>
> Michael
>King
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
>
************************************************
Lucas Haag
HCR 66 Box 25A
Bartley, Nebraska 69020-9717
Email: lhaag@.............. OR haag_cnslt@...........
World Wide Web: http://www.swnebr.net/~lhaag
************************************************
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: David A Nelson <dann@........>
Subject: test ignore
Date: Mon, 23 Jun 1997 21:44:40 +1200
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: jccowe@orion (Jacquie Cowe)
Subject: test
Date: Mon, 23 Jun 1997 13:00:18 -0700
test from iinet, pls reply
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From: "Giovanni Rotta" <rottag@..........>
Subject: R: test
Date: Mon, 23 Jun 1997 22:49:47 +0200
Ciao Jacquie !
Your email it's OK.
Regards,
Giovanni
rottag.@..........
----------
> Da: Jacquie Cowe <jccowe@orion>
> A: psn-l@.............
> Oggetto: test
> Data: lunedì 23 giugno 1997 22.00
>
> test from iinet, pls reply
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
_____________________________________________________________________
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From: roger baker <rcbaker@........>
Subject: Tech Talk
Date: Mon, 23 Jun 1997 15:54:21 -0500 (CDT)
Friends,
Since posting a review of the literature of seismometer
design a month or so ago, I have found an excellent article reviewing the
main considerations for the design of long period instruments.
The article is titled Limits of Sensitivity of Inertial Seismographs with
Velocity Transducers and Electronic Amplifiers from the Bulletin of the
Seismological Society of America, vol. 80, number 6, pp.1725-1752, by
Riedesel, Moore and Orcutt.
The lower and upper frequency limits of performance are determined by the
sensors mass, period, and Q, and by the amplifiers used with those
sensors. These sorts of considerations are explained very well in this
article as well as the selection of front end op amp electronics. The
goal of the authors was to logically examine long period options suitable
for ocean bottom seismometers, which generally means small and probably
battery powered.
Let me review what I have learned about seismometer design lately.
My understanding is that small inexpensive accelerometers like the
Humphrey being tested by Charles Patton and Erich Kern have as good as 30
microgravity sensitivity without being easily overloaded and are thus
presumably good for data collection during medium to large
disturbances--including the time when the big one hits.
Meanwhile vertical axis geophones have a near theoretical sensitivity at
a natural period of anywhere from one Hz or to 4 Hz or more, but most
geophones are highly resonant and rapidly lose sensitivity off band; at
the long periods necessary to study interesting distant quakes, with
lower natural frequency geophones with a period of one second or more,
however, being better in this regard.
On the other hand, many amateurs seem to be building critically damped
swinging gate type Lehmans with horizontal axis sensitivity. Most of the
displacement sensors are of the classical coil and magnet variety which
are used to measure velocity, despite the fact that such sensors tend to
be less sensitive for long periods, largely due to the fact that all
electronic amplifiers have more noise at very low frequencies; i.e.-- 1/f
noise. There are however good and fairly inexpensive low noise op amps
that can best be matched to the impedance of most common sensing coils,
as the article cited above discusses at length.
There is however, the option of using displacement transducers which by
definition sense position, rather than velocity as the coil and magnet
sensors do. A DC output signal is of inherent advantage for long period
sensing which should extend to 20 seconds with constant sensitivity, and
for the fascinating area of gravimeter design.
If you design a gravimeter sensitive enough to see the daily earth tides
caused by the sun and moon, you are measuring on the order of one
microgravity, and unless you low pass filter the output, you
automatically have a pretty good long period seismometer too, like it or
not. It is probably not too much of a stretch to say that good
seismometer designers, if they get good enough, may one day hope to
design good tidal gravimeters, which must take strong precautions against
long term drift, especially thermal drift. The one relaxed parameter for
gravimeter design is that short term Brownian noise can be better
filtered and averaged out so that much smaller masses suspended by
various kinds of springs are permissible, even down to a few milligrams.
Heavy damping is no problem here.
Arguably, the really important recent innovations in seismometer design
are the use of force feedback and the use of displacement sensors as
opposed to the classic magnet and coil velocity transducers.
The advantage of force feedback is that the mass is nearly stationary,
which means that its natural period is repressed and its sensitivity is
thus spread across the frequency spectrum, and particularly extended to
longer periods, but in a small package. Also, since the mass is kept
almost stationary at one given point, the linearity of the mass
suspension at other points becomes much less important.
Our design goal becomes to reduce the mass restoration force to nearly
zero at whatever point the feedback loop tries to hold it, equivalent to
hanging the mass from a weak spring. This is because if the position
restoring forces acting on the mass are made very small, equivalent to
hanging the mass from a long weak spring, the natural period of the
system will lengthen so we get more position displacement with less
energy. This leads to better instrumental sensitivity, which we want,
other things being equal.
Most manmade magnetic fields are quite non-linear, but in some ways this
assists them to nearly perfectly compensate the force of gravity over a
very small range of displacement -- a point set by the force feedback
loop. The electrical feedback signal output from such a system will act
as if it were accurately sensing the position of a mass on a very weak
but very long spring with linear displacement properties.
Another consideration is that the mass suspension system must have a very
high Q if possible, mechanically equivalent to a weight bobbing up and
down on a spring for a very long time. Thus sensitivity is how far the
spring stretches under a given force, while how long it bobs is the Q of
the system. If we have both virtues at the same time, it is the same as
saying that a very small amount of kinetic energy introduced once put
into the system will be stored as small oscillations for long time. This
is what we want on the mechanical side -- because a long oscillating
system is by its nature also mechanically capable of integrating the
energy of an acceleration force without loss over the ten or twenty
second period of a long seismic wave. Obviously, if there is any friction
in the oscillating system, then the very weak acceleration forces imposed
on a mass during a ten second teleseismic wave will get lost; for example
as heat in a spring, air friction, etc.
With all this in mind, I am currently concentrating on vertical axis
designs involving ceramic magnets bobbing around on razor blade
suspensions, and these systems have wonderfully high Qs, oscillating for
thousands of times before coming to rest. These periods may be lengthened
to a second or so with a 15 gram mass and knife edge beam only an inch or
two long, with most of the beam mass being in the ceramic magnet. A
simple feedback system uses an old relay coil mounted just under the beam
as a push-pull actuator to stabilize the horizontal mass beam.
One source of frustration during design has been the design of feedback
control circuits. Im not very good at math but resolved to plunge in
anyhow. Bad (inefficient) feedback systems are easy to stabilize whereas
good ones are hard to design and take lots of data and math and long
books to explain properly. But there is a practical no tears shortcut.
There are things called lag and lead networks. These are two simple high
and low pass filters in the ffedback loop that you can tweak and adjust
with a couple of potentiometers until the system response is stable and
fast, while managing to damp out the natural oscillation period fairly
well.
My current approach is to use a $25 laser pointer beam multiply reflected
between parallel mirrors and a phototransistor bridge as a displacement
detector. I use optics because everything is cheap and easy to set up and
you can tell at a glance whether the feedback loop is operating stably.
However there is the fall back option of a capacitance bridge micrometer
which is orders of magnitude more sensitive to small stationary
displacements than any other hackable option. The latter can be built out
of Radio Shack parts. I have such a circuit that Ill publish some time.
Sensitive capacitance micrometer sensors are fussy gadgets that take
comparatively more work to set up and tune, etc., compared to a laser beam.
--Yours, Roger Baker
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jean-Jacques HUNSINGER <jjh@............>
Subject: good book...
Date: Tue, 24 Jun 1997 00:06:47 +0200
David A Nelson wrote:
>
> John H.,
> an excellent text book to read is the the text for my
> university geophysics papers that I did it is called The Solid Earth,
> An Introduction to Global Geophysics. by C.M.R. Fowler
>
Hi Dave,
Could you tell me the editor's name ?
thanks.
jjh
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Al Allworth <aallworth@........>
Subject: Seattle area event
Date: Mon, 23 Jun 1997 15:15:36 -0700
Has anyone any info on an EQ in the Seallle area? I am now living in Gold
Beach, Oregon but have no equipment running yet. It came over satelite news.
____________________________________________________________________________
Al Allworth, Gold Beach, OR aallworth@........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Seattle area event
Date: Mon, 23 Jun 1997 16:54:04 -0600
The following information is from the University of Washington in
Seattle.
OT=97*06/23+19:13:27.05 Lat=47N35.91 Lon=122W34.46 Depth=7.21 Mag=4.9
Al Allworth wrote:
>
> Has anyone any info on an EQ in the Seallle area? I am now living in Gold
> Beach, Oregon but have no equipment running yet. It came over satelite news.
> ____________________________________________________________________________
>
> Al Allworth, Gold Beach, OR aallworth@........
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
PO Box 25046, Federal Center cranswick@........
Denver, CO 80225-0046 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Edward Cranswick <cranswick@........>
Subject: Re: Seattle area event
Date: Mon, 23 Jun 1997 17:02:08 -0600
The following information is from the NEIC.
DATE-(UTC)-TIME LAT LON DEP MAG Q COMMENTS
yy/mm/dd hh:mm:ss deg. deg. km
97/06/23 19:13:26 47.62N 122.57W 10.0 4.8Md A WASHINGTON
Al Allworth wrote:
>
> Has anyone any info on an EQ in the Seallle area? I am now living in Gold
> Beach, Oregon but have no equipment running yet. It came over satelite news.
> ____________________________________________________________________________
>
> Al Allworth, Gold Beach, OR aallworth@........
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
--
Edward Cranswick Tel: 303-273-8609
US Geological Survey, MS 966 Fax: 303-273-8600
PO Box 25046, Federal Center cranswick@........
Denver, CO 80225-0046 USA E.M. Forster said, "Only connect".
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: ACole65464@.......
Subject: Re: Seattle area event
Date: Mon, 23 Jun 1997 21:24:21 -0400 (EDT)
To Al Allworth,
The 4.9 Mag event occured less than 20 miles from my home (and seismometer)
here in western Washington, and it pegged out my strip chart recorder. The
seismometer that recorded it was a home made force feedback broadband
accelerometer with the output intergrated for a velocity signal. The main
event was followed by 3 lesser events of 2.0, 2.6 and 3.1 Mag, as of 6:00 pm
PDT tonight.
The origin time for the 4.9 was at:
19:13:27 6/23/97 UTC
47.58 N
122.56 W
7.4 Km deep
5.5 Km NE of Bremerton Wa.
The above info from the University of Washington.
Allan Coleman
P.S. One of these days I should start logging the seismic signals onto a
computer so I can easily share the files via the PSN.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: JACK HERRON <JHERRON@.........>
Subject: Re: test
Date: Mon, 23 Jun 1997 22:47:39 -0700
At 01:00 PM 6/23/97 -0700, you wrote:
>test from iinet, pls reply
>
>_____________________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email listserver@............. with the body of the
>message: leave PSN-L
>
-----------------------------------------
Jack Herron - Editor
Society for Amateur Scientists
8118 E. 20th St.
Tucson, AZ 85710 USA
jherron@.........
520 885-6933
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Sam Toon <serr15@...............>
Subject: Re: good book...
Date: Tue, 24 Jun 1997 08:47:11 BST
The book is:
The Solid Earth, An Introduction to Global Geophysics
Author: C.M.R. Fowler
Publisher: Cambridge University Press
ISBN 0-521-37025-6 hardback
ISBN 0-521-35890-3 paperback - price 19.95 UK pounds
Hope this helps,
Sam
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sam Toon serr15@.........
Microseismology Research Group http://www.liv.ac.uk/~serr15/Microseis/
Dept of Earth Sciences Tel: +44 (0)151 794 5157
University of Liverpool Fax: +44 (0)151 794 5157
P.O. Box 147, Liverpool, L69 3BX United Kingdom
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
_____________________________________________________________________
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From: David A Nelson <dann@........>
Subject: Re: good book...
Date: Tue, 24 Jun 1997 19:58:52 +1200
JJH and all,
The Solid Earth,
An Introduction to Global Geophysics. by C.M.R. Fowler
Cambridge University Press, reprinted 1992
ISBN 0-521-38590-3 soft cover ISBN 0-521-37025-6 hard
cover
should have included it for a start
Dave
Hi Dave,
>Could you tell me the editor's name ?
>thanks.
>jjh
Dave A. Nelson
24 Jensen St.,
Green Is., Dunedin,
South Is.. New Zealand.
http://psn.quake.net/dave/home.htm
Q-BIT'S LAW No.9: INTERCHANGEABLE PARTS- WON'T BE
Q-BIT'S LAW No.10: ANY WIRING ERROR IN ANY CONSTRUCTION WILL BE IN
THE DIRECTION OF THE MOST DAMAGE
Q-BIT'S LAW No.13: IDENTICAL PARTS AREN'T
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Clark Wockner <clark@.............>
Subject: Test do not read
Date: Fri, 27 Jun 1997 07:05:26 -0700
TEST TEST
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Jean-Yves Trudel <jtrudel@.........>
Subject: test
Date: Fri, 27 Jun 1997 16:13:06 -0700
Hi ! just to see if the list work,
Jean-Yves
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: JIM CRISTIANO <weitech@..........>
Subject: Re: test
Date: Fri, 27 Jun 1997 13:32:32 -0700
Jean-Yves Trudel wrote:
>
> Hi ! just to see if the list work,
> Jean-Yves
Yup, it's been pretty quiet out there.
jim cristiano@...........
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Public Seismic Network Mailing List (PSN-L)
From: "Rex Klopfenstein, Jr." <rklopfen@.........>
Subject: New Subscriber Questions
Date: Sat, 28 Jun 1997 18:18:05 -0400
I have been looking at the seismometer designs that are list on the PSN
home page. I notice that they are all horizontal. Are there any designs
for vertical seismographs?
I have been scouting the parts that are required to build a Lehman-type
seismometer. I noticed that Edmund sells the horseshoe magnetics for about
$50 each! I found a similar magnetic for $18. The company that
manufactures the magnetic is General and can be purchased at a supply
company called Grainger (McMaster-Carr most likely would have them also).
I think there is a Grainger branch in almost all large cities in the
midwest. This magnetic has a lift force of 30 pounds, 1-3/4" across with a
1-3/16" gap.
I also notice that most seismometer designer transmit their signals as
voltage levels. Has anybody thought about using current levels? The is a
standard current loop (4-20 mA) which is used by instrumentation users to
transmit their signals at large distances. This is rather easy to do,
several manufactures make IC's that do the conversions. Using these chips,
one can take a voltage signal and convert it into a current signal. At the
other end, an IC converts the current loop back to voltage level. The
current loop does not suffer from voltage drops. Also, a large number of
line protection and line devices are available for 4-20 mA current loops.
One word of caution with any long lines (voltage or current) which are run
outside, watch out for lightning strike damage to lines and equipment
attached--this includes lines that are run underground!! There are several
suppressor available to protect lines.
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: barry lotz <gbl@.......>
Subject: coil orientation
Date: Sat, 28 Jun 1997 15:06:14 -0700
Hi all
I have been toying with the most efficient way to orient the
coil/magnet assembly. The first orientation is like a solenoid with the
coil axis parallel to the direction of motion and the cylindrical magnet
at one end ,slightly inside the coil. The second is a "flatter" coil
oriented with the axis perpendicular to the direction of motion. There
is a magnet pair on each side of the coil disk and on opposite ends(180
deg.) apart. The polarity would have to be correct so the pairs don't
cancel each other. Anybody see that one is better than the other? I use
the second type with my Lehman and the first type as feedback for my
force balance unit. I would like to improve my force balance unit but am
not sure which way to wind the coil to get the highest output," all
other things being equal".
Barry
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Al Allworth <aallworth@........>
Subject: Re: coil orientation
Date: Sat, 28 Jun 1997 18:25:25 -0700
At 03:06 PM 6/28/97 -0700, you wrote:
>Hi all
> I have been toying with the most efficient way to orient the
>coil/magnet assembly.
Hello,
I have found that I get the most output when I use a coreless solenoid coil
about as long as the diameter and locate it so that it is close to the
horseshoe magnet and points at the gap between the poles. In this position
the flux is canceled at rest and increases in one polarity when that pole
approaches the center of the coil and likewise for the other polarity when
the other pole approaches the center of the coil. Any arrangement I have
come up with seems to be non-linear but this arrangement might be a little
better. I have not done any thorough measurement of linearity, just watched
the scope as the magnet was moved a short distance.
____________________________________________________________________________
Al Allworth, Gold Beach, OR aallworth@........
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Clark Wockner <clark@.............>
Subject: Re: New Subscriber Questions
Date: Sat, 28 Jun 1997 22:02:30 -0700
Hi Rex and all readers:
I just finnished my Lehman a couple of weeks ago and followed the coil
and magnet instructions found at
( Http:psn.quake.net/lehmnmod.html )
It is working fine. The cow magnets are, Three for $5.95 At Farm and
fleet stores here in Illinois.
Later Clark
Rex Klopfenstein, Jr. wrote:
>
> I have been looking at the seismometer designs that are list on the PSN
> home page. I notice that they are all horizontal. Are there any designs
> for vertical seismographs?
>
> I have been scouting the parts that are required to build a Lehman-type
> seismometer. I noticed that Edmund sells the horseshoe magnetics for about
> $50 each! I found a similar magnetic for $18. The company that
> manufactures the magnetic is General and can be purchased at a supply
> company called Grainger (McMaster-Carr most likely would have them also).
> I think there is a Grainger branch in almost all large cities in the
> midwest. This magnetic has a lift force of 30 pounds, 1-3/4" across with a
> 1-3/16" gap.
>
> I also notice that most seismometer designer transmit their signals as
> voltage levels. Has anybody thought about using current levels? The is a
> standard current loop (4-20 mA) which is used by instrumentation users to
> transmit their signals at large distances. This is rather easy to do,
> several manufactures make IC's that do the conversions. Using these chips,
> one can take a voltage signal and convert it into a current signal. At the
> other end, an IC converts the current loop back to voltage level. The
> current loop does not suffer from voltage drops. Also, a large number of
> line protection and line devices are available for 4-20 mA current loops.
> One word of caution with any long lines (voltage or current) which are run
> outside, watch out for lightning strike damage to lines and equipment
> attached--this includes lines that are run underground!! There are several
> suppressor available to protect lines.
>
>
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: Karl Cunningham <karlc@.......>
Subject: Re: New Subscriber Questions
Date: Sun, 29 Jun 1997 11:33:16 -0700
At 06:18 PM 6/28/97 -0400, you wrote:
>I have been looking at the seismometer designs that are list on the PSN
>home page. I notice that they are all horizontal. Are there any designs
>for vertical seismographs?
Hi Rex --
I've been doing some thinking about building a vertical seismometer, and
plan to build one in the future. There are others on the list with
considerably more experience than I; and hopefully they will catch any
errors I make here.
I believe the reason there aren't descriptions on the PSN web site is that
a vertical seismometer is considerably more difficult to build than a
horizontal one. The heart of the design is that you suspend a mass against
gravity (like weighing it) and then detect apparent changes in gravity,
which are really vertical movements of the earth. Many people want to
build seismometers that are sensitive enough and have instrument noise
levels low enough to detect background earth noise, since once reaching
that level, further improvements in sensitivity are pretty much pointless.
The earth background noise level (at least on a quiet day in my area) is
about 50 nano-g (50 billionths of gravity) at a 6-second period. I'd like
to get to 1 nano-g noise level for long-period work.
Other people build seismometers that don't get down to the background noise
level, which are just a useful (on closer/stronger events), and get
considerably easier to build.
To build a vertical seismometer to get to the background noise level, at
least three major problems crop up:
1. Suspending a mass against gravity with a period in the range of a few
seconds is not as easy as just hanging a weight from a screen-door closing
spring. Springs exert a force that is more or less proportional to the
amount they are stretched, which means you need a VERY long spring to get a
period of 5 seconds or so. Other mechanisms are often employed to make the
spring's force more constant over the distance the mass is to move, thus
lengthening the period. But that all makes the thing more complicated and
harder to build. (Force-balance designs get around this problem, but add
complexity.)
2. Variations in local barometric pressure will cause noise due to the
change in buoying force of the atmospheric pressure on the mass. Even the
pressure variations associated with small breezes can cause significant
noise. Two solutions exist for this problem. An air-tight housing (or
very nearly so), or the following: Incorporate a balance (teeter-totter
arrangement) with the mass on one side and a very light object of the same
volume on the other side. That way the buoying forces will cancel, but the
effect of inertial accelerations on the mass will not. Either approach
makes it more complicated and harder to build.
3. The mechanism suspending the mass (spring, magnetic levitation, etc.)
must be have stability good enough to not contribute significant noise.
Variations in spring constant with even small temperature changes are much
higher than this, and so are variations in magnetic field from common
magnets. I think the only way out of this is to make the suspension out of
the most temperature stable material you can find, and then do a lot of
insulating of the instrument against temperature changes.
Problem 3 is made more difficult by the nature of seismic signals. I'm not
sure what period signals you want to detect, but detecting teleseismic
events involves signals with periods into the tens of seconds. There are
two factors that both make things worse for longer-period signals:
1. As a fraction of gravity (or spring force), longer-period seismic
signals are smaller than those with shorter periods, by a factor roughly
equal to the ratio of the periods.
2. Thermal insulation is more difficult when one is trying to keep the
temperature constant for longer periods of time.
I'm certainly not trying to scare anyone off, and having more people
experimenting with home-made vertical seismometers would be great! But
understand that they are a more difficult animal to tame than a horizontal
one.
Karl Cunningham
La Mesa, CA.
karlc@.......
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: shammon1@.............
Subject: Re: New Subscriber Questions
Date: Sun, 29 Jun 1997 01:32:44 -0700
Karl Cunningham wrote:
Hi Karl and Rex,
I hate to disagree, but there is a vertical seismograph plan around
someplace on one of the BBS's. I know it is on my San Jose PSN BBS's
under the name VERTICAL.GIF. I scanned it in myself. It is a design done
by Terry Frost in Southern California and is so simple that a 7-year old
can build it.
It uses a coil and cow magnet, door spring, and aluminum channel.The
damping is done with an oil bath and plunger. Works great for local
events up to 500Km. I see you are down south, so call the PSN BBS in
Pasadena and you should be able to find the file. The BBS phone numbers
are on Larry's WEB page.
Regards, Steve Hammond
PSN San Jose, California
>
> At 06:18 PM 6/28/97 -0400, you wrote:
> >I have been looking at the seismometer designs that are list on the PSN
> >home page. I notice that they are all horizontal. Are there any designs
> >for vertical seismographs?
>
> Hi Rex --
>
> I've been doing some thinking about building a vertical seismometer, and
> plan to build one in the future. There are others on the list with
> considerably more experience than I; and hopefully they will catch any
> errors I make here.
>
> I believe the reason there aren't descriptions on the PSN web site is that
> a vertical seismometer is considerably more difficult to build than a
> horizontal one. The heart of the design is that you suspend a mass against
> gravity (like weighing it) and then detect apparent changes in gravity,
> which are really vertical movements of the earth. Many people want to
> build seismometers that are sensitive enough and have instrument noise
> levels low enough to detect background earth noise, since once reaching
> that level, further improvements in sensitivity are pretty much pointless.
> The earth background noise level (at least on a quiet day in my area) is
> about 50 nano-g (50 billionths of gravity) at a 6-second period. I'd like
> to get to 1 nano-g noise level for long-period work.
>
> Other people build seismometers that don't get down to the background noise
> level, which are just a useful (on closer/stronger events), and get
> considerably easier to build.
>
> To build a vertical seismometer to get to the background noise level, at
> least three major problems crop up:
>
> 1. Suspending a mass against gravity with a period in the range of a few
> seconds is not as easy as just hanging a weight from a screen-door closing
> spring. Springs exert a force that is more or less proportional to the
> amount they are stretched, which means you need a VERY long spring to get a
> period of 5 seconds or so. Other mechanisms are often employed to make the
> spring's force more constant over the distance the mass is to move, thus
> lengthening the period. But that all makes the thing more complicated and
> harder to build. (Force-balance designs get around this problem, but add
> complexity.)
>
> 2. Variations in local barometric pressure will cause noise due to the
> change in buoying force of the atmospheric pressure on the mass. Even the
> pressure variations associated with small breezes can cause significant
> noise. Two solutions exist for this problem. An air-tight housing (or
> very nearly so), or the following: Incorporate a balance (teeter-totter
> arrangement) with the mass on one side and a very light object of the same
> volume on the other side. That way the buoying forces will cancel, but the
> effect of inertial accelerations on the mass will not. Either approach
> makes it more complicated and harder to build.
>
> 3. The mechanism suspending the mass (spring, magnetic levitation, etc.)
> must be have stability good enough to not contribute significant noise.
> Variations in spring constant with even small temperature changes are much
> higher than this, and so are variations in magnetic field from common
> magnets. I think the only way out of this is to make the suspension out of
> the most temperature stable material you can find, and then do a lot of
> insulating of the instrument against temperature changes.
>
> Problem 3 is made more difficult by the nature of seismic signals. I'm not
> sure what period signals you want to detect, but detecting teleseismic
> events involves signals with periods into the tens of seconds. There are
> two factors that both make things worse for longer-period signals:
>
> 1. As a fraction of gravity (or spring force), longer-period seismic
> signals are smaller than those with shorter periods, by a factor roughly
> equal to the ratio of the periods.
>
> 2. Thermal insulation is more difficult when one is trying to keep the
> temperature constant for longer periods of time.
>
> I'm certainly not trying to scare anyone off, and having more people
> experimenting with home-made vertical seismometers would be great! But
> understand that they are a more difficult animal to tame than a horizontal
> one.
>
> Karl Cunningham
> La Mesa, CA.
> karlc@.......
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
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From: "Martin Brewer" <mbrewer@......>
Subject: Re: Bermuda 'quake
Date: Sun, 29 Jun 1997 16:40:34 -0300
----------
>On 20 June Robert L Barns wrote
>
> Re:your quake, a 4.9 at about 21:35 on 6/18. My map sez Bermuda is
~32N
> and 65W. This is 830 miles from me. A prog. I use to calc. relative
> signal strength here sez that I should have seen it far above my noise
> level. I saw nothing even though the Lehman was working well.
Dear Robert Barns,
Many thanks for your feedback. It is good to know that there is someone
relatively close by who can verify (or not) events "seen" here.
> I got a good 'gram from the SE Pacific Rise, 6/10, 21:53:45, m6.1 which
> had a rel. sig. only 1/3 of that for your event.
I must have just missed that event. The Bermuda station came on line just
afterwards.
I have just got back home from a week abroad and I haven't checked through
all the mail. But I do seem to have a trace of what looks like 6/24,
23:19:17, dist 9.26, 1030km, M4.4. Can you verify?
I look forward to comparing notes with you in the future.
Regards,
Martin
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From: barry lotz <gbl@.......>
Subject: Re: New Subscriber Questions
Date: Sun, 29 Jun 1997 13:07:26 -0700
Karl Cunningham wrote:
>
> At 06:18 PM 6/28/97 -0400, you wrote:
> >I have been looking at the seismometer designs that are list on the PSN
> >home page. I notice that they are all horizontal. Are there any designs
> >for vertical seismographs?
>
> Hi Rex --
>
> I've been doing some thinking about building a vertical seismometer, and
> plan to build one in the future. There are others on the list with
> considerably more experience than I; and hopefully they will catch any
> errors I make here.
>
> To build a vertical seismometer to get to the background noise level, at
> least three major problems crop up:
>
> 1. Suspending a mass against gravity with a period in the range of a few
> seconds is not as easy as just hanging a weight from a screen-door closing
> spring. Springs exert a force that is more or less proportional to the
> amount they are stretched, which means you need a VERY long spring to get a
> period of 5 seconds or so. Other mechanisms are often employed to make the
> spring's force more constant over the distance the mass is to move, thus
> lengthening the period. But that all makes the thing more complicated and
> harder to build. (Force-balance designs get around this problem, but add
> complexity.)
>
Hi
What I have had luck with in getting a long period vertical is to
have a beam with the hinge in the vertical direction (obvious I guess).
I used two knife edges at the same elevation and about 3" apart for the
hinge. The free end of the 24"-30" beam has the coil. The spring
attaches to the free end just behind the spring. At the hinge end it
attaches about 3" up. The closer the spring is to the hinge the longer
the period but the spring must be stiffer. I made the spring as long as
possible by attaching several smaller springs in series. I was able to
get a period approaching 20 sec. I am not sure how much mechanical noise
one would get from lateral motion of the spring during an event. I
suspect the lateral natural frequency of the spring is at least an order
of magnitude higher than teleseismic event frequencies.
Barry
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From: Robert Avakian <ravakian@............>
Subject: Re: New Subscriber Questions
Date: Sun, 29 Jun 1997 14:30:03 -0700
Vertical seismographs are indeed, gravimeters and some solutions might
be stolen from the LaCoste-Rhomberg meters. The thermal problem is
elminated by heating the enclosure to a constant, well above ambient
temperature. The insulation is minimal and the unit is thermostatically
controlled. [Would use of true DC power (batteries) eliminate
electromagnetic interference from the heating?] The cases are also
sealed with a gasket around the top perhaps making them less subject to
short period pressure variations.
I have used L-R meters as clouds passed over with no affect on the
readings while a recording barograph sitting next to me went berserk.
Of course, readings of 1/100 th milligal are quite a ways above your
noise level.
The L-R meters are long period. While using one on the Carrizo plain
(near the San Andreas) I routinely saw "swing" from local seisimic
activity whose longest period exceeeded 45 seconds per cycle.
Although the mechanism of the L-R is complex, could it be siplified
and scaled up?
One question. How did you measure your background to such a fine
precision? Did you use an existing horizontal machine or somthing
different?
Bob Avakian
Karl Cunningham wrote:
>
> At 06:18 PM 6/28/97 -0400, you wrote:
> >I have been looking at the seismometer designs that are list on the PSN
> >home page. I notice that they are all horizontal. Are there any designs
> >for vertical seismographs?
>
> Hi Rex --
>
> I've been doing some thinking about building a vertical seismometer, and
> plan to build one in the future. There are others on the list with
> considerably more experience than I; and hopefully they will catch any
> errors I make here.
>
> I believe the reason there aren't descriptions on the PSN web site is that
> a vertical seismometer is considerably more difficult to build than a
> horizontal one. The heart of the design is that you suspend a mass against
> gravity (like weighing it) and then detect apparent changes in gravity,
> which are really vertical movements of the earth. Many people want to
> build seismometers that are sensitive enough and have instrument noise
> levels low enough to detect background earth noise, since once reaching
> that level, further improvements in sensitivity are pretty much pointless.
> The earth background noise level (at least on a quiet day in my area) is
> about 50 nano-g (50 billionths of gravity) at a 6-second period. I'd like
> to get to 1 nano-g noise level for long-period work.
>
> Other people build seismometers that don't get down to the background noise
> level, which are just a useful (on closer/stronger events), and get
> considerably easier to build.
>
> To build a vertical seismometer to get to the background noise level, at
> least three major problems crop up:
>
> 1. Suspending a mass against gravity with a period in the range of a few
> seconds is not as easy as just hanging a weight from a screen-door closing
> spring. Springs exert a force that is more or less proportional to the
> amount they are stretched, which means you need a VERY long spring to get a
> period of 5 seconds or so. Other mechanisms are often employed to make the
> spring's force more constant over the distance the mass is to move, thus
> lengthening the period. But that all makes the thing more complicated and
> harder to build. (Force-balance designs get around this problem, but add
> complexity.)
>
> 2. Variations in local barometric pressure will cause noise due to the
> change in buoying force of the atmospheric pressure on the mass. Even the
> pressure variations associated with small breezes can cause significant
> noise. Two solutions exist for this problem. An air-tight housing (or
> very nearly so), or the following: Incorporate a balance (teeter-totter
> arrangement) with the mass on one side and a very light object of the same
> volume on the other side. That way the buoying forces will cancel, but the
> effect of inertial accelerations on the mass will not. Either approach
> makes it more complicated and harder to build.
>
> 3. The mechanism suspending the mass (spring, magnetic levitation, etc.)
> must be have stability good enough to not contribute significant noise.
> Variations in spring constant with even small temperature changes are much
> higher than this, and so are variations in magnetic field from common
> magnets. I think the only way out of this is to make the suspension out of
> the most temperature stable material you can find, and then do a lot of
> insulating of the instrument against temperature changes.
>
> Problem 3 is made more difficult by the nature of seismic signals. I'm not
> sure what period signals you want to detect, but detecting teleseismic
> events involves signals with periods into the tens of seconds. There are
> two factors that both make things worse for longer-period signals:
>
> 1. As a fraction of gravity (or spring force), longer-period seismic
> signals are smaller than those with shorter periods, by a factor roughly
> equal to the ratio of the periods.
>
> 2. Thermal insulation is more difficult when one is trying to keep the
> temperature constant for longer periods of time.
>
> I'm certainly not trying to scare anyone off, and having more people
> experimenting with home-made vertical seismometers would be great! But
> understand that they are a more difficult animal to tame than a horizontal
> one.
>
> Karl Cunningham
> La Mesa, CA.
> karlc@.......
>
> _____________________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email listserver@............. with the body of the
> message: leave PSN-L
_____________________________________________________________________
Public Seismic Network Mailing List (PSN-L)
From: roger baker <rcbaker@........>
Subject: Re: New Subscriber Questions
Date: Mon, 30 Jun 1997 00:03:56 -0500 (CDT)
Friends,
Since I am immersed in seismometer design at the moment, I
might as well comment too. So far as the LaCoste Romberg suspension is
concerned, this is a classic spring design that gives better linearity
for long period vertical forces. However force balancing makes the beam
nearly motionless, so you no longer care about linearity over any distance
and this clever idea loses its main advantage. What is more, force
balancing lets you make a short period instrument mimic the sensitivity of
a long period instrument. But only mechanical spring and mass combinations
that have a high Q can be used in this way.
The reason is that all spring
and mass combinations oscillate but some are damped so the oscillations
die down quickly. A high Q is natures way of telling you that a
system has inherently low losses and might be useful for our purposes.
If you are trying to measure long period waves with a long period beam,
you may try to damp the beam to eliminate overshoot, which otherwise
confuses the data. In the case of force balancing, however, the
balancing force itself is used to damp the beam and all other losses
within the system thus become undesirable and reduce sensitivity.
The exact counter-force needed to keep a high Q system motionless is
sensitive to long periods of waves as well as short. Force balancing
eliminates the oscillation,mostly, but the system still traps energy as
effectively as it did when it was permitted to oscillate freely. Only now
the situation is turned around and outside influences are exactly
represented as how much force is needed to keep the system perfectly
quiet in the presence of constantly added external energy.
As I have said before, it looks like magnetic suspension and knife blade
combinations have just the sort of high Q needed for vertically sensitive
magnetic force balancing seismometers. My device works and fits in a
small package, which tends to solve other problems like temperature
control--the current question is how well it works in comparison to more
conventional designs for long beam/long period vertical seismometers.
Sensitivity to stray magnetic field variations clearly is a potential
concern, but it may not add much noise in the teleseismic bands.
I don't currently have a web page to reveal the fine points, but I expect
to publish soon one way or another, and wish to be open about what I
fancy I have learned lately until then.
--Yours, Roger Baker
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From: Karl Cunningham <karlc@.......>
Subject: Re: New Subscriber Questions
Date: Sun, 29 Jun 1997 22:40:39 -0700
At 02:30 PM 6/29/97 -0700, you wrote:
> One question. How did you measure your background to such a fine
>precision? Did you use an existing horizontal machine or somthing
>different?
I have an existing calibrated horizontal FB seismometer running here and
have data on background noise in a variety of bandwidths.
Karl Cunningham
La Mesa, CA.
karlc@.......
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