Sent: Saturday, January 06, 2007 6:19 AM
Subject: Geophone with long legs
> Hi all
>
> I am wondering, since I did move my geophone back inside, is the
> geophone less sensitive becose he now stands on the legs but is not
> surrounded in sand like when I did have him outside. Does it matter in
> the terms of detecting earthquakes ?
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Rockland filter
From: Bob Barns royb1@...........
Date: Tue, 09 Jan 2007 11:11:20 -0500
With the usual 14 or 16 bit A/D's, is that dynamic range necessary?
Bob
ChrisAtUpw@....... wrote:
> In a message dated 08/01/2007, royb1@........... writes:
>
> There us currently a digital Rockland on ebay but it looks
> expensive and
> I don't know the specs. The analog version comes up occasionaly.
>
> Hi Bob,
>
> I haven't read the data manual for a Rockland Digital Filter, but
> the problem with digital filters for seismic use has previously been
> their low dynamic range. They are simply too noisy and may give less
> than 80 dB, where over 120 dB would be desirable.
>
> Regards,
>
> Chris Chapman
>
>
> __________ NOD32 1966 (20070109) Information __________
>
> This message was checked by NOD32 antivirus system.
> http://www.eset.com
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Reading a Seismogram
From: "tchannel" tchannel@..............
Date: Tue, 9 Jan 2007 18:50:13 -0700
Hi Folks, These questions may have to do with art and experience, as =
much as science. Can one explain how to read a Seismogram, if that is =
the correct word? That is the enlarged section of the recorded trace. =
I normally can find the P and S. I also understand the different =
directional movements, as illustrated in pictures I have seen.=20
1. Are the large waves that follow the S, surface waves?
2. If so can one discern Loves from Rayleigh's, within that section?
3. Do the Loves and Rayleigh's arrive at different times, as with P and =
S? and or, do the look different?
I am sure the more you work with these recordings the better you can =
interpret them.
A related question: I just recorded a very nice image of the 5.7m =
01/09/2007 Southeastern Alaska 2259km from Boise Idaho, using my =
Vertical Spring sensor. The best recording, so far, using this new =
sensor. I was please with the image; a clear P, a smaller but clear S, =
followed by a large series of waves, I assume, to be surface waves. But =
here I can't tell a Love from a Rayleigh. =20
I did not know a vertical spring sensor would pick up surface waves, =
even though the Rayleigh's could move the vertical spring. Is it that =
the vertical is less likely to pick up these waves at greater distances, =
because of their longer periods?
Thanks, Ted
Hi Folks, These questions may =
have to do with=20
art and experience, as much as science. Can one explain how to =
read a=20
Seismogram, if that is the correct word? That is the enlarged =
section of=20
the recorded trace. I normally can find the P and S. I also =
understand=20
the different directional movements, as illustrated in pictures I =
have=20
seen.
1. Are the large waves that =
follow the=20
S, surface waves?
2. If so can one discern Loves =
from=20
Rayleigh's, within that section?
3. Do the Loves and Rayleigh's =
arrive at=20
different times, as with P and S? and or, do the look=20
different?
I am sure the more you work with these =
recordings=20
the better you can interpret them.
A related question: I just =
recorded a very=20
nice image of the 5.7m 01/09/2007 Southeastern Alaska 2259km from Boise =
Idaho,=20
using my Vertical Spring sensor. The best recording, so far, =
using=20
this new sensor. I was please with the image; a clear P, a =
smaller=20
but clear S, followed by a large series of waves, I assume, to be =
surface=20
waves. But here I can't tell a Love from a Rayleigh. =
I did not know a vertical spring sensor =
would pick=20
up surface waves, even though the Rayleigh's could move the=20
vertical spring. Is it that the vertical is less likely to =
pick up=20
these waves at greater distances, because of their longer =
periods?
Thanks, Ted
Subject: Re: Reading a Seismogram
From: ChrisAtUpw@.......
Date: Tue, 9 Jan 2007 21:51:02 EST
In a message dated 10/01/2007, tchannel@.............. writes:
Hi Folks, These questions may have to do with art and experience, as much=20
as science. Can one explain how to read a Seismogram, if that is the corre=
ct=20
word? That is the enlarged section of the recorded trace. I normally can=20
find the P and S. I also understand the different directional movements, as=
=20
illustrated in pictures I have seen.=20
Hi Ted,
=20
I suggest that you download and print a copy of the seismic time travel=
=20
graph from _http://neic.usgs.gov/neis/travel_times/ttgraph.html_=20
(http://neic.usgs.gov/neis/travel_times/ttgraph.html) =20
=20
When an earthquake occurs, two types of wave are generated. The faster=20
compression P waves have their displacement in the direction of propagation=
..=20
The slower S shear waves have their displacement perpendicular to their=20
direction of propagation. Local frequency components up to a few hundred Hz=
may be=20
recorded, but these =E2=80=98high frequency=E2=80=99 components are rapidly=
absorbed as the=20
signals travel through the Earth.=20
When these waves reach the surface of the Earth, they generate slower=20
surface waves, which propagate radially outwards. The Love waves have the h=
igher=20
velocity and their displacement is perpendicular to the direction of=20
propagation in the plane of the surface. The Rayleigh waves are slower and=20=
have a=20
retrograde vertical motion in the direction of propagation.
The wave propagation is constrained by the transmission velocities in the=20
various Earth layers, the crust, the mantle and the cores. I suggest that=20=
you=20
download the seismograph training manual from=20
_http://psn.quake.net/info/analysis.pdf_ (http://psn.quake.net/info/analysis=
..pdf) Due to layering and the=20
curvature of the Earth, the seismic responses are divided into local (0 to=20
1.4 deg), near regional (1.4 to 6 deg.), regional (6 to 16 deg.) and=20
teleseismic responses (16 to 180 deg.). The angle is that between the sour=
ce and the=20
observer at the centre of the Earth. See p 12. A 1 degree angle correspond=
s=20
to 111.3 km, 69.2 miles or 60 nautical mile at the surface.
The P and S waves have frequencies between 0.5 and maybe 40 Hz, with the S=20
waves having a bit less than =C2=BD the period of the associated P waves. P=
waves=20
from regional and teleseismic events may have frequencies between 1 and 3 H=
z.=20
The L and R surface waves may have periods up to several hundred seconds=20
depending on the physical dimensions of the seismic slip, but for smaller q=
uakes=20
they are more typically between 10 and 30 seconds. The amplitude of Rayleig=
h=20
waves of about 20 sec period are often measured to determine the magnitude=20=
of=20
a quake. For Local and Near Regional quakes, the amplitudes of the P or S=20
waves may be used to determine the quake magnitude.
Visual seismic displays are described at=20
_http://www.geol.binghamton.edu/faculty/jones/_ (http://www.geol.binghamton.=
edu/faculty/jones/)=20
download seisvole.readme and download the program SeismicEruptionSetup.exe
While the surface waves radiate outwards in a fairly simple and predictable=
=20
manner, the waves within the earth generate new wave pairs at every=20
refraction and reflection. The response to a large quake depends on the dep=
th of the=20
quake as well as the angle between it and the observer and can get very =20
complicated.
1. Are the large waves that follow the S, surface waves?
Yes, but see the time travel graph
2. If so can one discern Loves from Rayleigh's, within that section?
The Love waves have the higher velocity and are horizontally polarised.
The Rayleigh waves are a bit slower and are vertically polarised.
3. Do the Loves and Rayleigh's arrive at different times, as with P and S?=
=20
and or, do the look different?
=20
I am sure the more you work with these recordings the better you can=20
interpret them.
=20
A related question: I just recorded a very nice image of the 5.7m 01/09/200=
7=20
Southeastern Alaska 2259km from Boise Idaho, using my Vertical Spring=20
sensor. The best recording, so far, using this new sensor. I was please wi=
th the=20
image; a clear P, a smaller but clear S, followed by a large series of wave=
s,=20
I assume, to be surface waves. But here I can't tell a Love from a Rayleig=
h.
Note that the surface waves are polarised. A vertical sensor will pick=20
up mostly Rayleigh waves. A Lehman will pick up mostly Love waves
I did not know a vertical spring sensor would pick up surface waves, eve=
n=20
though the Rayleigh's could move the vertical spring. Is it that the =20
vertical is less likely to pick up these waves at greater distances, because=
of=20
their longer periods?
A sensor will still react to motions at less than it's resonant period,=
=20
but the amplitude of the response decreases with the square of the ratio of=
=20
the resonant period to the wave period. So if your vertical sensor has a=20
period of 2 secs, a typical Rayleigh wave of 20 seconds will show about 1/1=
00 the=20
'normal' sensitivity.
=20
Regards,
=20
Chris Chapman
In a message dated 10/01/2007, tchannel@.............. writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>
Hi Folks, These questions may have=20=
to do=20
with art and experience, as much as science. Can one explain how to=20=
read=20
a Seismogram, if that is the correct word? That is the enlarged sect=
ion=20
of the recorded trace. I normally can find the P and S. I also=20
understand the different directional movements, as illustrated in=20
pictures I have seen.
Hi Ted,
I suggest that you download and print a copy of=
the=20
seismic time travel graph from
http://neic.usg=
s.gov/neis/travel_times/ttgraph.html
When an earthquake occurs, two types of wave ar=
e=20
generated. The faster compression P waves have their displacement in the=20
direction of propagation. The slower S shear waves have their displacement=20
perpendicular to their direction of propagation. Local frequency components=20=
up=20
to a few hundred Hz may be recorded, but these =E2=80=98high frequency=E2=
=80=99 components are=20
rapidly absorbed as the signals travel through the=20
Earth.
When these waves reach the surface o=
f=20
the Earth, they generate slower surface waves, which propagate radially=20
outwards. The Love waves have the higher velocity and their displacement is=20
perpendicular to the direction of propagation in the plane of the surface. T=
he=20
Rayleigh waves are slower and have a retrograde vertical motion in the direc=
tion=20
of propagation.
The wave propagation is constrain=
ed=20
by the transmission velocities in the various Earth layers, the crust, the=20
mantle and the cores. I suggest that you download the seismograph trai=
ning=20
manual from
http://psn.quake.net/info/an=
alysis.pdf =20
Due to layering and the curvature of the Earth, the seismic responses are=20
divided into local (0 to 1.4 deg), near regional (1.4 to 6 deg.), regional (=
6 to=20
16 deg.) and teleseismic responses (16 to 180 deg.). The angle is that=
=20
between the source and the observer at the centre of the Earth. See p 12.&nb=
sp;=20
A 1 degree angle corresponds to 111.3 km, 69.2 miles or 60 nautical mile at=20=
the=20
surface.
The P and S waves have frequencies betwe=
en=20
0.5 and maybe 40 Hz, with the S waves having a bit less than =C2=BD the peri=
od of the=20
associated P waves. P waves from regional and teleseismic events may have=20
frequencies between 1 and 3 Hz. The L and R surface waves may have periods u=
p to=20
several hundred seconds depending on the physical dimensions of the seismic=20
slip, but for smaller quakes they are more typically between 10 and 30 secon=
ds.=20
The amplitude of Rayleigh waves of about 20 sec period are often measured to=
=20
determine the magnitude of a quake. For Local and Near Regional quakes, the=20
amplitudes of the P or S waves may be used to determine the quake=20
magnitude.
Visual seismic displays are described at http://www.geol.bingh=
amton.edu/faculty/jones/download seisvole.readme and download the=20
program SeismicEruptionSetup.exe
While the=20
surface waves radiate outwards in a fairly simple and predictable manner, th=
e=20
waves within the earth generate new wave pairs at every refraction and=20
reflection. The response to a large quake depends on the depth of the quake=20=
as=20
well as the angle between it and the observer and can get very=20
complicated.
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>
1. Are the large waves that fo=
llow the=20
S, surface waves?
Yes, but see the time travel graph
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>
2. If so can one discern Loves from=
=20
Rayleigh's, within that section?
The Love waves have the higher velocity and are=
=20
horizontally polarised.
The Rayleigh waves are a bit slower and are=20
vertically polarised.
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>
3. Do the Loves and Rayleigh's arri=
ve at=20
different times, as with P and S? and or, do the look=20
different?
I am sure the more you work with these re=
cordings=20
the better you can interpret them.
A related question: I just recorded=20=
a very=20
nice image of the 5.7m 01/09/2007 Southeastern Alaska 2259km from Boise Id=
aho,=20
using my Vertical Spring sensor. The best recording, so far, using t=
his=20
new sensor. I was please with the image; a clear P, a smaller but clear S,=
=20
followed by a large series of waves, I assume, to be surface waves.=20=
But=20
here I can't tell a Love from a Rayleigh.
Note that the surface waves are polarised. A=20
vertical sensor will pick up mostly Rayleigh waves. A Lehman will pick up mo=
stly=20
Love waves
I=20
did not know a vertical spring sensor would pick up surface waves, even th=
ough=20
the Rayleigh's could move the vertical spring. Is it that the=20
vertical is less likely to pick up these waves at greater distances, becau=
se=20
of their longer periods?
A sensor will still react to motions at less th=
an=20
it's resonant period, but the amplitude of the response decreases with the=20
square of the ratio of the resonant period to the wave period. So if your=20
vertical sensor has a period of 2 secs, a typical Rayleigh wave of 20 second=
s=20
will show about 1/100 the 'normal' sensitivity.
Regards,
Chris Chapman
Subject: Re: Rockland filter
From: ChrisAtUpw@.......
Date: Tue, 9 Jan 2007 21:58:00 EST
In a message dated 09/01/2007 16:16:40 GMT Standard Time, royb1@...........
writes:
With the usual 14 or 16 bit A/D's, is that dynamic range necessary?
Bob
Hi Bob,
A 16 bit ADC with no noise has +/-1/2 bit uncertainty. This is about 96
dB. Each factor of 2 gives 6 dB change. With +/-10V input 1 bit = 0.305 mV
Quiet opamps may give 0.1 to 10 Hz input noise levels well below 1 micro
volt; true chopper amplifiers may be much less than this. The CAZ opamps
tend to give 1 to 2 micro volts, but these may give OK results for long period
signals, when 1/f drifts become large. It is a good principle to use odd
orders of low pass filter with a capacitor across the feedback resistor of the
first opamp. Never amplify high frequency signals. This limits the effect of
intermodulation distortion and subharmonics
Digital filters tend to give performance in the mid 70 dBs, or less, but
also suffer from switch transient feed through - 5 mV? - which may need
additional analogue filtering before putting it into an ADC.
In seismometry, we are seeking very low noise levels at very low
frequencies. You just can't afford to throw away +/-4 bits signal through a poor
choice of filter, or +/-3 bits by failing to average out the internal ADC noise.
While you can increase the amplifier gain to display small signals over
internal noise, a reduction of the range by a factor of 8 or more is very
undesirable.
Your available dynamic range is usually far less than the maximum range
of signals that you can receive.
If you use a Lehman or similar long period sensor, you should set your
background microseism signal to maybe 200 counts. If you don't do this, you
may not be able to sense the long period low amplitude signals masked by the
microseism background.
Regards,
Chris Chapman
In a message dated 09/01/2007 16:16:40 GMT Standard Time, royb1@comcast=
..net=20
writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>With the=20
usual 14 or 16 bit A/D's, is that dynamic range=20
necessary?
Bob
Hi Bob,
A 16 bit ADC with no noise has +/-1/2 bit=20
uncertainty. This is about 96 dB. Each factor of 2 gives 6 dB change. With=20
+/-10V input 1 bit =3D 0.305 mV
Quiet opamps may give 0.1 to 10 Hz input noise=20
levels well below 1 micro volt; true chopper amplifiers may be much less tha=
n=20
this. The CAZ opamps tend to give 1 to 2 micro volts, but these may give OK=20
results for long period signals, when 1/f drifts become large. It is a good=20
principle to use odd orders of low pass filter with a capacitor across the=20
feedback resistor of the first opamp. Never amplify high frequency signals.=20=
This=20
limits the effect of intermodulation distortion and subharmonics
Digital filters tend to give performance in the=
mid=20
70 dBs, or less, but also suffer from switch transient feed through - 5 mV?=20=
-=20
which may need additional analogue filtering before putting it into an=20
ADC.
In seismometry, we are seeking very low noise=20
levels at very low frequencies. You just can't afford to throw away +/-4 bit=
s=20
signal through a poor choice of filter, or +/-3 bits by failing to average o=
ut=20
the internal ADC noise. While you can increase the amplifier gain to=20
display small signals over internal noise, a reduction of the range by a fac=
tor=20
of 8 or more is very undesirable.
Your available dynamic range is usually far=20=
less=20
than the maximum range of signals that you can receive.
If you use a Lehman or similar long period sens=
or,=20
you should set your background microseism signal to maybe 200 counts. If you=
=20
don't do this, you may not be able to sense the long period low amplitude=20
signals masked by the microseism background.
Regards,
Chris Chapman
Subject: Re: Reading a Seismogram
From: "tchannel" tchannel@..............
Date: Wed, 10 Jan 2007 10:22:35 -0700
Hi Chris, Thanks again! Extremely well written and very useful reply. =
Linda my wife, an English major, worked as an report specialist and =
editor for 31 years, working with scientific publications.......She will =
also enjoy reading this.
Cheers, Ted
----- Original Message -----=20
From: ChrisAtUpw@..........
To: psn-l@.................
Sent: Tuesday, January 09, 2007 7:51 PM
Subject: Re: Reading a Seismogram
In a message dated 10/01/2007, tchannel@.............. writes:
Hi Folks, These questions may have to do with art and experience, =
as much as science. Can one explain how to read a Seismogram, if that =
is the correct word? That is the enlarged section of the recorded =
trace. I normally can find the P and S. I also understand the different =
directional movements, as illustrated in pictures I have seen.=20
Hi Ted,
I suggest that you download and print a copy of the seismic time =
travel graph from http://neic.usgs.gov/neis/travel_times/ttgraph.html=20
When an earthquake occurs, two types of wave are generated. The =
faster compression P waves have their displacement in the direction of =
propagation. The slower S shear waves have their displacement =
perpendicular to their direction of propagation. Local frequency =
components up to a few hundred Hz may be recorded, but these =
=E2=80=98high frequency=E2=80=99 components are rapidly absorbed as the =
signals travel through the Earth.=20
When these waves reach the surface of the Earth, they generate =
slower surface waves, which propagate radially outwards. The Love waves =
have the higher velocity and their displacement is perpendicular to the =
direction of propagation in the plane of the surface. The Rayleigh waves =
are slower and have a retrograde vertical motion in the direction of =
propagation.
The wave propagation is constrained by the transmission velocities =
in the various Earth layers, the crust, the mantle and the cores. I =
suggest that you download the seismograph training manual from =
http://psn.quake.net/info/analysis.pdf Due to layering and the =
curvature of the Earth, the seismic responses are divided into local (0 =
to 1.4 deg), near regional (1.4 to 6 deg.), regional (6 to 16 deg.) and =
teleseismic responses (16 to 180 deg.). The angle is that between the =
source and the observer at the centre of the Earth. See p 12. A 1 =
degree angle corresponds to 111.3 km, 69.2 miles or 60 nautical mile at =
the surface.
The P and S waves have frequencies between 0.5 and maybe 40 Hz, =
with the S waves having a bit less than =C2=BD the period of the =
associated P waves. P waves from regional and teleseismic events may =
have frequencies between 1 and 3 Hz. The L and R surface waves may have =
periods up to several hundred seconds depending on the physical =
dimensions of the seismic slip, but for smaller quakes they are more =
typically between 10 and 30 seconds. The amplitude of Rayleigh waves of =
about 20 sec period are often measured to determine the magnitude of a =
quake. For Local and Near Regional quakes, the amplitudes of the P or S =
waves may be used to determine the quake magnitude.
Visual seismic displays are described at =
http://www.geol.binghamton.edu/faculty/jones/
download seisvole.readme and download the program =
SeismicEruptionSetup.exe
While the surface waves radiate outwards in a fairly simple and =
predictable manner, the waves within the earth generate new wave pairs =
at every refraction and reflection. The response to a large quake =
depends on the depth of the quake as well as the angle between it and =
the observer and can get very complicated.
1. Are the large waves that follow the S, surface waves?
Yes, but see the time travel graph
2. If so can one discern Loves from Rayleigh's, within that =
section?
The Love waves have the higher velocity and are horizontally =
polarised.
The Rayleigh waves are a bit slower and are vertically polarised.
3. Do the Loves and Rayleigh's arrive at different times, as with P =
and S? and or, do the look different?
I am sure the more you work with these recordings the better you can =
interpret them.
A related question: I just recorded a very nice image of the 5.7m =
01/09/2007 Southeastern Alaska 2259km from Boise Idaho, using my =
Vertical Spring sensor. The best recording, so far, using this new =
sensor. I was please with the image; a clear P, a smaller but clear S, =
followed by a large series of waves, I assume, to be surface waves. But =
here I can't tell a Love from a Rayleigh.
Note that the surface waves are polarised. A vertical sensor will =
pick up mostly Rayleigh waves. A Lehman will pick up mostly Love waves
I did not know a vertical spring sensor would pick up surface =
waves, even though the Rayleigh's could move the vertical spring. Is it =
that the vertical is less likely to pick up these waves at greater =
distances, because of their longer periods?
A sensor will still react to motions at less than it's resonant =
period, but the amplitude of the response decreases with the square of =
the ratio of the resonant period to the wave period. So if your vertical =
sensor has a period of 2 secs, a typical Rayleigh wave of 20 seconds =
will show about 1/100 the 'normal' sensitivity.
Regards,
Chris Chapman
=EF=BB=BF
Hi Chris, Thanks again! Extremely well written =
and very=20
useful reply. Linda my wife, an English major, worked as an report =
specialist and editor for 31 years, working with scientific=20
publications.......She will also enjoy reading this.
Cheers, Ted
----- Original Message -----
From:=20
ChrisAtUpw@.......
Sent: Tuesday, January 09, 2007 =
7:51=20
PM
Subject: Re: Reading a =
Seismogram
In a message dated 10/01/2007,
tchannel@..............=20
writes:Hi Folks, These questions may =
have to do=20
with art and experience, as much as science. Can one explain =
how to=20
read a Seismogram, if that is the correct word? That is the =
enlarged=20
section of the recorded trace. I normally can find the P and =
S. I also=20
understand the different directional movements, as illustrated =
in=20
pictures I have seen.
Hi Ted,
I suggest that you download and print a =
copy of=20
the seismic time travel graph from
http://neic.=
usgs.gov/neis/travel_times/ttgraph.html
When an earthquake occurs, two types of =
wave are=20
generated. The faster compression P waves have their displacement in =
the=20
direction of propagation. The slower S shear waves have their =
displacement=20
perpendicular to their direction of propagation. Local frequency =
components up=20
to a few hundred Hz may be recorded, but these =E2=80=98high =
frequency=E2=80=99 components are=20
rapidly absorbed as the signals travel through the=20
Earth.
When these waves reach the =
surface of=20
the Earth, they generate slower surface waves, which propagate =
radially=20
outwards. The Love waves have the higher velocity and their =
displacement is=20
perpendicular to the direction of propagation in the plane of the =
surface. The=20
Rayleigh waves are slower and have a retrograde vertical motion in the =
direction of propagation.
The wave =
propagation is=20
constrained by the transmission velocities in the various Earth =
layers, the=20
crust, the mantle and the cores. I suggest that you download the =
seismograph training manual from
http://psn.quake.net/info=
/analysis.pdf =20
Due to layering and the curvature of the Earth, the seismic responses =
are=20
divided into local (0 to 1.4 deg), near regional (1.4 to 6 deg.), =
regional (6=20
to 16 deg.) and teleseismic responses (16 to 180 deg.). The =
angle is=20
that between the source and the observer at the centre of the Earth. =
See p=20
12. A 1 degree angle corresponds to 111.3 km, 69.2 miles or 60 =
nautical=20
mile at the surface.
The P and S waves have =
frequencies between 0.5 and maybe 40 Hz, with the S waves having a bit =
less=20
than =C2=BD the period of the associated P waves. P waves from =
regional and=20
teleseismic events may have frequencies between 1 and 3 Hz. The L and =
R=20
surface waves may have periods up to several hundred seconds depending =
on the=20
physical dimensions of the seismic slip, but for smaller quakes they =
are more=20
typically between 10 and 30 seconds. The amplitude of Rayleigh waves =
of about=20
20 sec period are often measured to determine the magnitude of a =
quake. For=20
Local and Near Regional quakes, the amplitudes of the P or S waves may =
be used=20
to determine the quake magnitude.
Visual seismic displays are =
described at http://www.geol.bi=
nghamton.edu/faculty/jones/download seisvole.readme and download the=20
program SeismicEruptionSetup.exe
While =
the=20
surface waves radiate outwards in a fairly simple and predictable =
manner, the=20
waves within the earth generate new wave pairs at every refraction and =
reflection. The response to a large quake depends on the depth of the =
quake as=20
well as the angle between it and the observer and can get very=20
complicated.
1. Are the large waves =
that follow=20
the S, surface waves?
Yes, but see the time travel graph
2. If so can one discern =
Loves from=20
Rayleigh's, within that section?
The Love waves have the higher velocity =
and are=20
horizontally polarised.
The Rayleigh waves are a bit slower and =
are=20
vertically polarised.
3. Do the Loves and =
Rayleigh's arrive at=20
different times, as with P and S? and or, do the look=20
different?
I am sure the more you work with =
these=20
recordings the better you can interpret them.
A related question: I just =
recorded a very=20
nice image of the 5.7m 01/09/2007 Southeastern Alaska 2259km from =
Boise=20
Idaho, using my Vertical Spring sensor. The best recording, so =
far,=20
using this new sensor. I was please with the image; a clear P, a =
smaller but=20
clear S, followed by a large series of waves, I assume, to be =
surface=20
waves. But here I can't tell a Love from a=20
Rayleigh.
Note that the surface waves are =
polarised. A=20
vertical sensor will pick up mostly Rayleigh waves. A Lehman will pick =
up=20
mostly Love waves
I=20
did not know a vertical spring sensor would pick up surface waves, =
even=20
though the Rayleigh's could move the vertical spring. Is =
it that=20
the vertical is less likely to pick up these waves at greater =
distances,=20
because of their longer periods?
A sensor will still react to motions at =
less than=20
it's resonant period, but the amplitude of the response decreases with =
the=20
square of the ratio of the resonant period to the wave period. So if =
your=20
vertical sensor has a period of 2 secs, a typical Rayleigh wave of 20 =
seconds=20
will show about 1/100 the 'normal' sensitivity.
Regards,
Chris=20
Chapman
Subject: Re: Reading a Seismogram
From: George Bush ke6pxp@.......
Date: Wed, 10 Jan 2007 09:46:41 -0800
Ted-
Larry Cochrane has provided some great tools right in Winquake. He allows
you to see the time of the various phases. To see these, set your P and S
times and than pull-down VIEW, select Phases and click the right button
and click DISPLAY and all of the phases of the various waves are
displayed as labelled red lines on your display. If I see some strong
waves on the graph while using WINQUAKE, I do this and try to understand
what is happening.
At 06:50 PM 1/9/2007 -0700, you wrote:
>>>>
Hi Folks, These questions may have to do with art and experience, as
much as science. Can one explain how to read a Seismogram, if that is
the correct word? That is the enlarged section of the recorded trace. I
normally can find the P and S. I also understand the different
directional movements, as illustrated in pictures I have seen.
1. Are the large waves that follow the S, surface waves?
2. If so can one discern Loves from Rayleigh's, within that section?
3. Do the Loves and Rayleigh's arrive at different times, as with P and
S? and or, do the look different?
I am sure the more you work with these recordings the better you can
interpret them.
A related question: I just recorded a very nice image of the 5.7m
01/09/2007 Southeastern Alaska 2259km from Boise Idaho, using my Vertical
Spring sensor. The best recording, so far, using this new sensor. I
was please with the image; a clear P, a smaller but clear S, followed by
a large series of waves, I assume, to be surface waves. But here I can't
tell a Love from a Rayleigh.
I did not know a vertical spring sensor would pick up surface waves, even
though the Rayleigh's could move the vertical spring. Is it that the
vertical is less likely to pick up these waves at greater distances,
because of their longer periods?
Thanks, Ted
<<<<<<<<
George
Subject: Wave Id's
From: "tchannel" tchannel@..............
Date: Thu, 11 Jan 2007 11:08:20 -0700
Hi All, It was pointed out that within Winquake software is a pulldown =
menu which places the various wave id markers. Is there a page avail =
which explains what the id's initials stand for? As an example P=3D =
primary S=3D secondary SSS,? LQ, LR and so on.
Thanks, Ted
Hi All, It was pointed out that =
within=20
Winquake software is a pulldown menu which places the various wave id=20
markers. Is there a page avail which explains what the id's =
initials stand=20
for? As an example P=3D primary S=3D secondary SSS,? LQ, LR =
and so=20
on.
Thanks, Ted
Subject: Earthquake swarm
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Thu, 11 Jan 2007 19:13:36 +0000
Hi all
Today around 17:23 UTC a earthquake swarm did start, this earthquake
swarm is about 150 km away from my location. Earthquake dection is from
good to poor, depending on size and fracture. I do not know how long
this earthquake swarm is going to last, but I do not belive it is over
when I write this at 19:13 UTC.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Wave Id's
From: John or Jan Lahr JohnJan@........
Date: Thu, 11 Jan 2007 11:22:54 -0800
Ted,
There is a free PC program that is great for understanding many of
the phases on a seismogram.
I always find the web site via google: alan jones seismic
Alan's site will be the first hit.
Download the program SeismicWaves from his site. This program shows
how the wave fronts
progress through the Earth, bouncing, converting, and refracting at
the major layers. At the same
time, actual seismograms are displayed as they would have looked when
being recorded. The
phases are labeled on the seismograms as they arrive. The
earthquakes are generally played
in speeded up time, as otherwise it would take 20 minutes to see the
first waves reach all the
way through the Earth.
For a full list of phases and ray-path diagrams, check out this site:
http://www.isc.ac.uk/Documents/IASPEI/sspl.html
Note that in some of the diagrams, where the paths for P and S are the same,
paths are labeled P/S, which means P or S. Similarly, Pdiff and Sdiff paths
are shown with the same red line.
Cheers,
John
At 10:08 AM 1/11/2007, you wrote:
>Hi All, It was pointed out that within Winquake software is a
>pulldown menu which places the various wave id markers. Is there a
>page avail which explains what the id's initials stand for? As an
>example P= primary S= secondary SSS,? LQ, LR and so on.
>
>Thanks, Ted
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Vertical sensor
From: "tchannel" tchannel@..............
Date: Thu, 11 Jan 2007 17:09:47 -0700
Hi Folks, In the last week or two, I have been testing my Vertical =
sensor, I have received several events.
I have a question about two: I don't remember the details of each =
event. =20
One event was due East about 400 miles, the other was due South about =
400 miles, they were both about 3.5M
The vertical recorded the one from the South just fine, but recorded =
nothing on the one from the East.
The vertical sensor is pointing N/S. If this was a Horz sensor I =
would expect this, but is a Vertical also, sensitive to the direction?
The hinge I made does keep the arm from moving left/right similar to the =
AS1.
Thanks, Ted
Hi Folks, In the last week or =
two, I have=20
been testing my Vertical sensor, I have received several =
events.
I have a question about two: I =
don't remember=20
the details of each event.
One event was due East about 400 miles, =
the other=20
was due South about 400 miles, they were both about 3.5M
The vertical recorded the one from the =
South just=20
fine, but recorded nothing on the one from the East.
The vertical sensor is pointing=20
N/S. If this was a Horz sensor I would expect this,=20
but is a Vertical also, sensitive to the direction?
The hinge I made does keep the arm from =
moving=20
left/right similar to the AS1.
Thanks, Ted
Subject: Kuril island 8.2Mw earthquake
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Sat, 13 Jan 2007 09:31:33 +0000
Hi all
I did record the 8.2Mw Kuril Island earthquake, it appears so good that
it is even visable on my online helcorder (plots). But that is really
unusual for a earthquake that is nearly 7200 km away from me.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Kuril island 8.2Mw earthquake <<< EUREKA>>>>>>
From: jimo17@........
Date: Sat, 13 Jan 2007 18:14:26 -0800
Hi Jon-
Eureka<<< Your geophones are working well.....M8.2 at ~8,000 kms
Always impressive to see an inexpensive jug doing amazing things..
Some Comments to improve your Recordings:
Before filtering observe the Power Spectra and decide what is signal and
noise peaks.
1. Look at Spectra- notice peak around 0.01-0.1
2. Use BP filter with 2 poles filter around 0.01-0.1, or some where in
that vicinity.
Remember the tighter the BP the more ringing you create in the
filtered record- I like a decade but you can use less.
Results will show the S arrivals and Surface waves much clearer.
Use option to mark these arrivals for you.
4. On the Teleseismic events consider resampling from 100 Hz (100 SPS) to
25 Hz to reduce the # of samples by 1/4.
5. You can also put in the Equalizer (electronic) circuit to change the
4.5 Hz to ~0.4Hz, which makes a big difference.
Keep up the good work as you are really doing well.
I can remember well when I recorded my first Teleseismic event with the
L15b-4.5Hz jug<<<<< Jim
Jim O'Donnell
Geological/Geophysical Consultant
GEOTECHNICAL APPLICATIONS
Las Vegas, Nevada
geophysics@..........
On Sat, 13 Jan 2007 09:31:33 +0000 =?ISO-8859-1?Q?J=F3n_Fr=EDmann?=
writes:
> Hi all
>
> I did record the 8.2Mw Kuril Island earthquake, it appears so good
> that
> it is even visable on my online helcorder (plots). But that is
> really
> unusual for a earthquake that is nearly 7200 km away from me.
>
> Regards.
> --
> Jón Frímann
> http://www.jonfr.com
> http://www.simnet.is/jonfr500/earthquake/
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Kuril island 8.2Mw earthquake <<< EUREKA>>>>>>
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Mon, 15 Jan 2007 14:00:22 +0000
Hi
I will soon add long period channels to my hardware and a long period
sensor too. So I don't have any reason to extend the geophone down to
that level.
The frequancy of the Kuril island 8.2Mw earthquake was hig enugh so that
I was able to see on frequancyes above 4Hz, even well above 10Hz. That
is unusual. I did lowpass it down to 4Hz for cleanup on the signal.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Kuril island 8.2Mw earthquake
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Tue, 16 Jan 2007 13:16:31 +0000
Hi all
emsc-csem has intresting info on the Kuril island earthquakes, both of
the large earthquake that have struck here with less then 60 days
between them.
Here is the url,
http://www.emsc-csem.org/index.php?page=current&sub=recent&evt=20061115_KURILS
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Earthquake lockin in Iceland
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Tue, 16 Jan 2007 19:17:40 +0000
Hi all
Iceland appears to be going trugh a rather strange event. This week,
that is Monday to today (16.01.2007) there have only been like 10
earthquakes in whole Iceland. Usaual by this time of the week, IMO has
recored learny 50 - 100 earthquakes, in a normal week. I call this
earthquake lockin, that means that something in the earth crust is stuck
and prevents earthquakes. What it is anybody guess. This was ongoing all
of 2006 and it is still going on. I don't think this good sign at all.
Whatever happen, there is a good chance it happens soon and is going to
be a large type of event, but what type of event I have no idea. There
is a chance a volcano is (in my opinion) that createing this tensions in
the crust.
This is just my speculation.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Noobie Greetings
From: "Michael Kimzey, D.O." mckimzey@...........
Date: Tue, 16 Jan 2007 20:51:31 -0500
Hi all.
I'm new to the group and just wanted to get my feet wet with a post,
observations and some questions. After many years of indecision, I finally
made the plunge and built a Lehman. It is currently operating in a crawl
space under the family room. I thought that it would be somewhat quiet
there, but it seems that some poured concrete over dirt isn't that quiet.
Additionally, I am 50 feet from a fairly busy road...but I'll take what I
can get.
With the help of Larry (very helpful and patient with questions), I got
the electronics up and running and the rest of the story with pictures can
be viewed at http://www.mckimzey.com/seismology.html I haven't seen any
activity yet, but did get a teaser with the recent Alaska quake...would have
recorded it but that was the 12 hours that the system was down for some
early modifications....hummf.
Right now I'm oil damped, but hope to make the metal damper. I have seen
that both copper and aluminum are used. Is either better than the other? I
don't have ready access to copper plate (is it available at Home Depot or
Lowes?) so I was going to use a pipe that I flattened. What kind of
thickness is needed?
I'm running WinSDR and I fiddled around with the gain on the board. Is
there a baseline count that I should aim for...I think that someone put it
at around 100 or 200 (boy, that 4th quarter list archive was looong). Also,
does it matter if I display raw or filtered data? I'm using the default
WinSDR settings for alarms and filters.
Finally, now that I've got the bug, of course I want more instruments. I
was thinking about the SG sensor, but the volksmeter has my interest piqued.
I heard that it might only be ready-made, but maybe it wouldn't be too
difficult to build one. The upright(s) of aluminum; shaft of aluminum
(although the PDF looks like it was made of brass). The plates could be
made of PCB board, etched if needed. It would just be the electronics that
I would need to buy. One of the things that I find neat about that design
is that it probably could be minimized to a size where it could fit in a 6
inch tube and be sunk several feet/meters in the ground (with remote motor
leveling and such)
Ok, enough of my ideas. My ignorance of seismology betrays me. Any
thoughts or ideas would be welcome. Thanks!
- Mike
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: Larry Cochrane lcochrane@..............
Date: Wed, 17 Jan 2007 02:11:30 -0800
Hi Mike,
Welcome to the group. When setting the gain you should use the raw data from the A/D
converter, so you should use the unfiltered data.
Regards,
Larry Cochrane
Redwood City, PSN
Michael Kimzey, D.O. wrote:
> Hi all.
>
> I'm new to the group and just wanted to get my feet wet with a post,
> observations and some questions. After many years of indecision, I finally
> made the plunge and built a Lehman. It is currently operating in a crawl
> space under the family room. I thought that it would be somewhat quiet
> there, but it seems that some poured concrete over dirt isn't that quiet.
> Additionally, I am 50 feet from a fairly busy road...but I'll take what I
> can get.
> With the help of Larry (very helpful and patient with questions), I got
> the electronics up and running and the rest of the story with pictures can
> be viewed at http://www.mckimzey.com/seismology.html I haven't seen any
> activity yet, but did get a teaser with the recent Alaska quake...would have
> recorded it but that was the 12 hours that the system was down for some
> early modifications....hummf.
>
> Right now I'm oil damped, but hope to make the metal damper. I have seen
> that both copper and aluminum are used. Is either better than the other? I
> don't have ready access to copper plate (is it available at Home Depot or
> Lowes?) so I was going to use a pipe that I flattened. What kind of
> thickness is needed?
>
> I'm running WinSDR and I fiddled around with the gain on the board. Is
> there a baseline count that I should aim for...I think that someone put it
> at around 100 or 200 (boy, that 4th quarter list archive was looong). Also,
> does it matter if I display raw or filtered data? I'm using the default
> WinSDR settings for alarms and filters.
>
> Finally, now that I've got the bug, of course I want more instruments. I
> was thinking about the SG sensor, but the volksmeter has my interest piqued.
> I heard that it might only be ready-made, but maybe it wouldn't be too
> difficult to build one. The upright(s) of aluminum; shaft of aluminum
> (although the PDF looks like it was made of brass). The plates could be
> made of PCB board, etched if needed. It would just be the electronics that
> I would need to buy. One of the things that I find neat about that design
> is that it probably could be minimized to a size where it could fit in a 6
> inch tube and be sunk several feet/meters in the ground (with remote motor
> leveling and such)
>
> Ok, enough of my ideas. My ignorance of seismology betrays me. Any
> thoughts or ideas would be welcome. Thanks!
>
> - Mike
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: "Dewayne" n0ssy@...........
Date: Wed, 17 Jan 2007 08:48:25 -0700
Welcome to the group Michael.
If you want to build a vertical seismometer, look at my design @
http://www.jclahr.com/science/psn/hill/.
I constructed this one about two years ago and it has preformed very well.
My seismometer is also located in my crawl space. I poured a small 4'x4'x6"
concrete pad to set my seismometers on. I used straight
mortar (lots of dust) as it doesn't contain any rocks. I used mortar to
prevent any thermo-dynamic differences between the mortar and rocks
that are in concrete.
I am using an oil dampimg system. I have tried cooking oil, transmisson
fluid and motor oil. All of these are not heavy enough to give a good
damping. My next try is going to be STP oil treatment. If STP don't work
I'll have to redo the tub to something with a larger surface area.
Anyway good luck and have fun.
Dewayne
----- Original Message -----
From: "Michael Kimzey, D.O."
To:
Sent: Tuesday, January 16, 2007 6:51 PM
Subject: Noobie Greetings
> Hi all.
>
> I'm new to the group and just wanted to get my feet wet with a post,
> observations and some questions. After many years of indecision, I
> finally made the plunge and built a Lehman. It is currently operating in
> a crawl space under the family room. I thought that it would be somewhat
> quiet there, but it seems that some poured concrete over dirt isn't that
> quiet. Additionally, I am 50 feet from a fairly busy road...but I'll take
> what I can get.
> With the help of Larry (very helpful and patient with questions), I
> got the electronics up and running and the rest of the story with pictures
> can be viewed at http://www.mckimzey.com/seismology.html I haven't
> seen any activity yet, but did get a teaser with the recent Alaska
> quake...would have recorded it but that was the 12 hours that the system
> was down for some early modifications....hummf.
>
> Right now I'm oil damped, but hope to make the metal damper. I have seen
> that both copper and aluminum are used. Is either better than the other?
> I don't have ready access to copper plate (is it available at Home Depot
> or Lowes?) so I was going to use a pipe that I flattened. What kind of
> thickness is needed?
>
> I'm running WinSDR and I fiddled around with the gain on the board. Is
> there a baseline count that I should aim for...I think that someone put it
> at around 100 or 200 (boy, that 4th quarter list archive was looong).
> Also, does it matter if I display raw or filtered data? I'm using the
> default WinSDR settings for alarms and filters.
>
> Finally, now that I've got the bug, of course I want more instruments. I
> was thinking about the SG sensor, but the volksmeter has my interest
> piqued. I heard that it might only be ready-made, but maybe it wouldn't be
> too difficult to build one. The upright(s) of aluminum; shaft of aluminum
> (although the PDF looks like it was made of brass). The plates could be
> made of PCB board, etched if needed. It would just be the electronics
> that I would need to buy. One of the things that I find neat about that
> design is that it probably could be minimized to a size where it could fit
> in a 6 inch tube and be sunk several feet/meters in the ground (with
> remote motor leveling and such)
>
> Ok, enough of my ideas. My ignorance of seismology betrays me. Any
> thoughts or ideas would be welcome. Thanks!
>
> - Mike
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with the body of the
> message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: "Dewayne" n0ssy@...........
Date: Wed, 17 Jan 2007 08:48:25 -0700
Welcome to the group Michael.
If you want to build a vertical seismometer, look at my design @
http://www.jclahr.com/science/psn/hill/.
I constructed this one about two years ago and it has preformed very well.
My seismometer is also located in my crawl space. I poured a small 4'x4'x6"
concrete pad to set my seismometers on. I used straight
mortar (lots of dust) as it doesn't contain any rocks. I used mortar to
prevent any thermo-dynamic differences between the mortar and rocks
that are in concrete.
I am using an oil dampimg system. I have tried cooking oil, transmisson
fluid and motor oil. All of these are not heavy enough to give a good
damping. My next try is going to be STP oil treatment. If STP don't work
I'll have to redo the tub to something with a larger surface area.
Anyway good luck and have fun.
Dewayne
----- Original Message -----
From: "Michael Kimzey, D.O."
To:
Sent: Tuesday, January 16, 2007 6:51 PM
Subject: Noobie Greetings
> Hi all.
>
> I'm new to the group and just wanted to get my feet wet with a post,
> observations and some questions. After many years of indecision, I
> finally made the plunge and built a Lehman. It is currently operating in
> a crawl space under the family room. I thought that it would be somewhat
> quiet there, but it seems that some poured concrete over dirt isn't that
> quiet. Additionally, I am 50 feet from a fairly busy road...but I'll take
> what I can get.
> With the help of Larry (very helpful and patient with questions), I
> got the electronics up and running and the rest of the story with pictures
> can be viewed at http://www.mckimzey.com/seismology.html I haven't
> seen any activity yet, but did get a teaser with the recent Alaska
> quake...would have recorded it but that was the 12 hours that the system
> was down for some early modifications....hummf.
>
> Right now I'm oil damped, but hope to make the metal damper. I have seen
> that both copper and aluminum are used. Is either better than the other?
> I don't have ready access to copper plate (is it available at Home Depot
> or Lowes?) so I was going to use a pipe that I flattened. What kind of
> thickness is needed?
>
> I'm running WinSDR and I fiddled around with the gain on the board. Is
> there a baseline count that I should aim for...I think that someone put it
> at around 100 or 200 (boy, that 4th quarter list archive was looong).
> Also, does it matter if I display raw or filtered data? I'm using the
> default WinSDR settings for alarms and filters.
>
> Finally, now that I've got the bug, of course I want more instruments. I
> was thinking about the SG sensor, but the volksmeter has my interest
> piqued. I heard that it might only be ready-made, but maybe it wouldn't be
> too difficult to build one. The upright(s) of aluminum; shaft of aluminum
> (although the PDF looks like it was made of brass). The plates could be
> made of PCB board, etched if needed. It would just be the electronics
> that I would need to buy. One of the things that I find neat about that
> design is that it probably could be minimized to a size where it could fit
> in a 6 inch tube and be sunk several feet/meters in the ground (with
> remote motor leveling and such)
>
> Ok, enough of my ideas. My ignorance of seismology betrays me. Any
> thoughts or ideas would be welcome. Thanks!
>
> - Mike
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with the body of the
> message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: "tchannel" tchannel@..............
Date: Wed, 17 Jan 2007 09:09:15 -0700
Hi Mike, Congratulations on a nice design, I build two Lehman's and a
Vertical, email me if you would like to see pictures as I have no way to
post them. Your Lehman should work great. My Lehman is in the basements
and I pick up Earthquakes fine, but also pick up road construction, digging
in the earth. I do not pick up any traffic, not even trucks, just weather,
cold fronts, and the city daytime noises.
I also used a ball bearing on my arm, but retained it between two drill bit
shanks. The ball ride in between the two cylinders so it does not move up
or down out of the small "V" formed by the shanks. Let us know when you
record your first event and maybe you will post them on .PSN
EVENTS. Ted
----- Original Message -----
From: "Michael Kimzey, D.O."
To:
Sent: Tuesday, January 16, 2007 6:51 PM
Subject: Noobie Greetings
> Hi all.
>
> I'm new to the group and just wanted to get my feet wet with a post,
> observations and some questions. After many years of indecision, I
> finally made the plunge and built a Lehman. It is currently operating in
> a crawl space under the family room. I thought that it would be somewhat
> quiet there, but it seems that some poured concrete over dirt isn't that
> quiet. Additionally, I am 50 feet from a fairly busy road...but I'll take
> what I can get.
> With the help of Larry (very helpful and patient with questions), I
> got the electronics up and running and the rest of the story with pictures
> can be viewed at http://www.mckimzey.com/seismology.html I haven't
> seen any activity yet, but did get a teaser with the recent Alaska
> quake...would have recorded it but that was the 12 hours that the system
> was down for some early modifications....hummf.
>
> Right now I'm oil damped, but hope to make the metal damper. I have seen
> that both copper and aluminum are used. Is either better than the other?
> I don't have ready access to copper plate (is it available at Home Depot
> or Lowes?) so I was going to use a pipe that I flattened. What kind of
> thickness is needed?
>
> I'm running WinSDR and I fiddled around with the gain on the board. Is
> there a baseline count that I should aim for...I think that someone put it
> at around 100 or 200 (boy, that 4th quarter list archive was looong).
> Also, does it matter if I display raw or filtered data? I'm using the
> default WinSDR settings for alarms and filters.
>
> Finally, now that I've got the bug, of course I want more instruments. I
> was thinking about the SG sensor, but the volksmeter has my interest
> piqued. I heard that it might only be ready-made, but maybe it wouldn't be
> too difficult to build one. The upright(s) of aluminum; shaft of aluminum
> (although the PDF looks like it was made of brass). The plates could be
> made of PCB board, etched if needed. It would just be the electronics
> that I would need to buy. One of the things that I find neat about that
> design is that it probably could be minimized to a size where it could fit
> in a 6 inch tube and be sunk several feet/meters in the ground (with
> remote motor leveling and such)
>
> Ok, enough of my ideas. My ignorance of seismology betrays me. Any
> thoughts or ideas would be welcome. Thanks!
>
> - Mike
>
>
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__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: =?ISO-8859-1?Q?J=F3n_Fr=EDmann?= jonfr500@.........
Date: Wed, 17 Jan 2007 17:51:59 +0000
Hi Michael
Welcome to this hobby. This is quite intresting hobby, when there is
something going on. But we also see some dead time too, when there is
nothing going on. I have one 4.5Hz sensor connected at the moment. But I
have plans to have more sensor up and running soon. I also have plans to
add three long period sensors to my system.
Check out my webpage, but you can see there my plots and other plots
also.
Regards.
--
Jón Frímann
http://www.jonfr.com
http://www.simnet.is/jonfr500/earthquake/
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Noobie Greetings
From: "tchannel" tchannel@..............
Date: Wed, 17 Jan 2007 17:41:02 -0700
Hi Mike, As to your damper, I too started with fluids, The magnetic
damper, that Chris told me about works like a champ. He has this design
posted. In your cast , you have lots of room, so you could hang an Alum or
Copper plate from your arm and have it pass between the magnet
sandwich/assm. sliding it in or out as needed. It allows you to move the
magnetic closer for a stronger effect. I use a piece of Alum about
1/16-1/8"? thick. It was a Alum lid for a plastic elect. project box,
Radioshack, the box came with a plastic lid and and Alum lid.
Ted
---