___________________________________________________________________________ Homebuilt Seismograph - FAQ Revised 12/22/96 ___________________________________________________________________________ Frequently people ask if it is possible for the lay person to monitor earthquakes as a hobby. The answer is, YES. Is it feasible? Maybe... Seismic sensors are quite easy to build. The problem in the past has been with timing. The age of the personal computer has solved much that problem for us. The key components for an amateur seismographic station are the same as for the professionals: 1) the sensor 2) preamplifier 3) low pass filter 4) amplifier 5) analog-to-digital converter 6) computer program for the collection of data 7) computer and monitor for the display of the data 8) printer (or drum recorder), if you want to print the seismograms Commercial personal seismographs are available for under $500.00. However, the software used and the file formats are not compatible with that used by most of the other amateur seismologist. Therefore, you would not be able to exchange files with others if you used one of the commercial collection systems. This may or may not be a problem depending on if you want to share data and/or view other seismograms. The most popular data collection program used by amateurs is EMON (Earth MONitor), written by Ted Blank. It allows the collection of up to 3 different sensors (Vertical, Horizontal N-S, and Horizontal E-W). It has multiple lines of display to show the data collected in a simulated on-screen seismogram. The user sets the threshold of acceptable noise to ignore. Once the signal exceeds the threshold for a specified number of samples the data is automatically saved to a file and the program goes back to monitoring. Ted has advised that he has a beta version of EMON in testing (May 95) that now supports data collection from 3 sensors simultaneously. Another useful feature is that the alarms can be set to trigger when a file is saved *or* when a quake is detected. The threshold for notification can also be set by the user. Another collection program, called SDR (for Seismic Data Recorder) is also available via the Internet. SDR also allows you to monitor multiple channels (up to 4 sensors) of data input simultaneously. Unlike EMON, it *requires* a VGA/SVGA monitor and a PC-LAB-711s Analog-to-Digital card or Larry Cochrane's 12 or 16 bt A/D card (see http://www.seismicnet.com/atod.html) installed in your IBM PC. It costs a bit more to run due to the equipment requirements but offers some advantages over the original version of EMON. One of the features that I like best is the ability to set *independant* alarms that will trigger on acqusition of waveforms that exceed a user selectable threshold from the combined sensors. Another useful function is the ability to have the alarm disable itself at a specified time. This is especially important to users who monitor radio telemetry since some of the remote sensors send a calibration signal at a regular time. By setting the auto-disable function the alarm will let you sleep every night when the calibration signal is sent. SDR also save all data to the disk drive so you can later replay the data and produce a PSN compatable event file. This normally produces a ~5 meg per channel per day. Quakeview - also written by Ted Blank, is a popular data viewing program for the files collected by EMON or SDR. A newer program called WINQUAKE has been written by Larry Cochrane but must run under a Windows environment. Both are available via FTP . WINQUAKE can also display the information collected from either EMON or SDR. It provides a time line across the bottom of the screen, an amplitude scale along the left margin and moveable markers for P and S wave onsets. WINQUAKE calculates magnitude and distance based upon marker placement. It allows various points to be cut and saved to files. It also displays FFT. Backgrounds, colors and options are user selectable. WINQUAKE also allows the user to import data from the finger servers and append it to the text windows to describe the recorded event on the seismogram. A 32 bit version of WinQuake is now available for Windows 95 and Windows NT. See http://www.seismicnet.com/software.html so more information. EMON or SDR and WINQUAKE make for a very nice package for the home seismograph. All three programs are available on from Internet ftp sites and from the Public Seismic Network Bulletin Boards located at several locations throughout the United States (listed below). One source of frustration for seismologist, amateur and professional alike, is noise. It's more of a problem for amateurs since the installations usually are placed where we live - in urban environments - near cars, trucks, and trains. All of these produce noise in the frequency ranges that are sensitive to the seismic sensor. There are several approaches to seismic monitoring: 1) Build your own sensor and record your own seismograms. (described below) 2) purchase a commercially available amateur package. 3) Decode radio telemetry from remote locations sent to central processing sites. Intercept data from USGS or universities. (see the REFERENCE section) ___________________________________________________________________________ CONSTRUCTION INFORMATION - INSTRUMENTS & SENSORS: A very good article was published several years ago in the AMATEUR SCIENTIST by Scientific American. Titled, "How To Build A Simple Seismograph to Record Earthquake Waves at Home" by Jearl Walker. The article was published in Scientific American, 1979, v. 241, No.1, pg 152-161. It described the construction of a horizontal seismic sensor and preamp circuit designed by James D. Lehman. At the time, Mr. Lehman was with the Physics Dept., James Madision University, Harrisonburg, Va., 22807. Aside: No one seems to know if the Lehman(n) sensor is named after the author, James D. Lehman, or the famed Danish seismologist, Inge Lehmann, who published a paper in 1936, that postulated that the earth held an inner core estimated to be about the size of our moon within the outer core. If someone has some information on this please forward it to me so I can include it in the next update of the FAQ. (kjn@........... Another source of information that describes modification to the Lehmann sensor was published in the: Journal of Geological Education, 1987, v.35, pg. 124 by Richard Lawrence Koll Dept. of Geology and Meteorology Kean College of New Jersey Union, NJ, 07083 The modifications of the Lehmann sensor include the use of common pipe fittings to construct the frame and support for the sensor. Construction is simple and straightforward. The amplifier, however, was prone to significant noise and oscillation. Newer circuits and components are available that eliminate this problem. Following instructions in the article a very sensitive horizontal sensor can be made for under $50.00 from parts available from the local hardware store. The parts list should be 3/4" pipe fittings and include: 2 flanges for bolting the assembly to a base. 2 3/4" T fittings 2 3/4" 90 degree elbows 1 3/4" union 4 3/4" nipples 2" long 2 3/4" nipples 6" long ___ 1 3/4" nipple 5" long | | |_v_| Assemble the parts to make a frame shaped like _|_^_|_ the v is the union and forms the resting point for the ^ the pendulum. Diagrams for sensors and pendulums, in the form of .GIF files, are available at FTP addresses listed later in this FAQ . Another sensor project is described in 2 consecutive issues of: EVERYDAY ELECTRONICS Allen House, East Borough, Wimborne, Dorset BH21 1PF, England. Vol. 18, No. 10, Oct. 1989 - the electronics part Vol. 18, No. 11, Nov. 1989 - the mechanical part Added 10/27/96 by Larry Cochrane ---------------------------------------- From: David Mawdsley I have read the Homebuilt Seismograph FAQ, and I wrote of to 'Everyday Electronics' for their two issues from 1989 that describe how to make a seismograph that is mentioned in the FAQ. You might like to know that they published another version of the seismograph in the September and October 1994 issues. The idea is almost identical to the 1989 articles, but a Hall Effect sensor is used instead of two coils of wire. They charged me '2.50 for each issue, although they could only give me a photocopy of the November 89 article (again at) 2.50). All those prices were with postage, in the UK. ______________________________ One comment in regards to damping. The original plans call for aluminium plates moving thru a magnetic field for damping the movement of the pendulum. Copper performs MUCH better than aluminium. If you can replace the aluminium with a copper plate of the same size you will notice a significant improvement. A good size for a 36" boom would be a piece of copper plate 1/4" thick x 4" square. Some users prefer to use oil damping to reduce boom motion. They equip the boom with vertical vanes that drag thru a bowl of mineral oil. (Tupperware works well if you can sneak a piece from the kitchen...) If you try this method to damp boom motion use the minimum amount of oil to accomplish the task. The amount will depend upon the mass of the boom but it doesn't take much to overdamp the boom! If you do use too much oil then the sensor will not move freely and you will miss some events. If you use too little you will see the data trace wander as it reaches resonance. Use an eye dropper to add or remove mineral oil from the dish or bowl. ___________________________________________________________________________ Long period sensors (for amateur installations) have periods up to about 20 secs. Short period sensors have periods of 1-2 secs. Long period Lehmann sensors are sensitive enough to detect large earthquakes several thousand miles away. Assistance can be obtained from others who have built their own monitoring stations via the Internet and the PSN BBS. The USENET newsgroup ca.earthquakes on Internet is a good place to start. sci.geo.earthquakes and sci.geo.geology are others. The PSN operates several BBS nodes throughout the country. Phone numbers for these are: (901) 360-0302 PSN Memphis, Tn. Charlie Rond, Sysop (818) 797-0536 PSN Pasadena, Ca. Dorothy & Jerry Darby, Sysops (408) 226-0675 PSN San Jose, Ca. Steve Hammond, Sysop ___________________________________________________________________________ Newsgroups: sci.geo.geology Subject: Need Seismometers Date: 24 Mar 1995 03:29:35 -0500 QUESTION: Who makes commercial seismometers? In the past I have made my own, but now I need a source for lots of nearly identical basic horizontal seimometers. I cut off at about 2 Hz and do some DSP for ground motion. Reliable shipping locks are essential. ANSWER (as of 3/31/95): A few companies making seismometers are: Mark Products -- Houston 713-498-0600 FAX -8707 Oyo Geospace -- Houston 713-937-5800 FAX -1161 Western Geo. Expl. Products -- Houston 713-331-6451 FAX -5245 Wards Natural Science Establishment out of Rochester, NY. 1-800-962-2660 For good used equipment you might try: Mitcham Industries -- Huntsville, TX 409-291-2277 FAX-295-1922 COMMENT: This From: Charles Young I would recommend a source for used geophones: R. T. Clark Companies, Inc. P.O. Box 20957 Oklahoma City, OK 73156 (405) 672-9400 They handle all kinds of used geophysical exploration equipment. They normally deal in lots of stuff costing thousands of dollars, and may be a little surprised if someone wants to buy in oneseys and twoseys, but they are friendly enough people and they will probably tolerate hobbyists. Typical prices on relevant items from their spring 1995 catalog are: 4.5 Hz Geophones $20 to @..... each Mark Products L4-C 1 Hz Seismometers $375 each (these are the REALLY good ones... and cost $850 new) ___________________________________________________________________________ Commercially available AMATEUR Seismometers are also available. If you'd rather purchase a commercial unit instead of building one (cost in the $400 - $500 range), you might check out the AS-2 SEISMIC RECORDING SYSTEM Available from: The Amateur Seismologist 2155 Verdugo Blvd., #528 Montrose, Ca 91020 (818)-249-1759 (New Address as of 6/19/94) *The manufacturer states: "With your order, you will receive a seismometer, a computer interface, software, and a complete instruction manual. The seismometer consists of a horizontal pendulum, and a transducer that produces a signal which is proportional to the velocity of the ground. This signal is then fed to a computer interface which plugs into the printer port of your computer. With the included software, this signal can be displayed on your computer in real time. If a quake is detected, the software automatically saves the data for later analysis." Information packets and plots of some of the quakes they have recorded are reportedly available upon request. * NOTE: [No endorsement is intended by the writer of the FAQ since I have not had the opportunity to evaluate the product.] Another source from Chuck: I have an ad from a company that makes a PC add-on seismograph. GEOSense Inc 115 W. California Blvd. #304 Pasadena, CA 91105 He says, "The cost is $450. You get software, an external 15 bit A/D and an `oil exploration ground velocity sensor'. eg an exploration type geophone. [Chuck's] guess is that its a 4.5 Hz geophone. [He] talked to them on the phone and they said they would be willing to add a jack so that any other sensor could be used. ----------- Added 07/08/96 by Larry Cochrane Another relatively inexpensive home PC based seismograph system is available from GeoTool 455 Vista Roma Newport Beach, CA 92660 Web Page: http://www.geotool.com Prices: Three Channel Seismograph System...............$ 599.00 Single Channel Seismograph System - Specify Horizontal or Vertical Geophone.....$ 299.00 Additional Channel.............................$ 150.00 ___________________________________________________________________________ REFERENCES: A reading list for general and specific information regarding earthquakes: Elementary Seismology by Charles F. Richter W. H. Freeman Publishers, New York, 1958 (out of print but available in some libraries) ------------------------------------------------------------------- Introduction to Seismology by Markus Bath, 1973, John Wiley&Sons, New York. ------------------------------------------------------------------- One of the best books that I have found for general information is EARTHQUAKES AND GEOLOGICAL DISCOVERY by Bruce Bolt, 1993 Scientific American Library, distributed by W.H. Freeman & Co. ISBN 0-7167-5040-6 available thru most bookstores. ------------------------------------------------------------------- Bruce bolt is a Professor of Seismology and former Director of the UC Berkely Seismographic Stations. In his book he discusses seismology, the various waves and their propagation, plate tectonics, how and why scientist study earth- quakes and how earthquakes affect buildings. Quite an undertaking in a mere 225 pages! It has some excellent photos and illistrations and is an easy read. Radio Telemetry: Monitoring Times, Vol. 13, No. 7, July, 1994, pg. 10 -14 Discusses aspects of intercepting and displaying the data transmitted from university or government seismic sensors. ___________________________________________________________________________ QUESTIONS & COMMENTS: Frequently asked questions From: cochrane@.............. (Larry Cochrane) Subject: Re: Personal Seismic Network? FAQ? Date: Thu, 21 Apr 1994 01:40:06 GMT RE: People's Seismic Network First, it's the *Public* Seismic Network. PSN has 4 bulletin boards around the country, the access numbers are: San Jose, Ca 1(408)226-0675 Steve Hammond, Sysop Pasadena, Ca 1(818)797-0536 Dorothy & Jerry Darby, Sysops Memphis, Tenn 1(901)360-0302 Charlie Rond, Sysop There is also a gopher site at gopher.ceri.memst.edu Port 70 I also have some of the PSN files in my ftp directory at: ftp.netcom.com /pub/cochrane. (also check Larry's FTP site at www.seismicnet.com or http://www.seismicnet.com for additional files) >If you are part of the PS network, would a 1 axis seismometer be helpful? Most PSN stations only have one sensor, it would be nice to have three, two horizontal, one pointed north-south and the other west-east, and one vertical sensor. My Lehman (a horizontal seismometer) is pointed north-south since most of the local quakes I receive here in Redwood City (between San Jose and San Francisco) Ca. originate north or south of me. This sensor can also receive quakes from all over the world. I was able to get a 7.3 in Indonesia a few months ago. The plans to build a Lehamn are in file lemansei.zip on any of the PSN systems and my ftp directory. >How about a Endevco accelerometer (also 1 axis). I think that accelerometers are only good for strong motion detection. To receive magnitude 3's 100km-200km away, or large distant quakes, you need a sensor that is very sensitive to very small ground motions. I don't know if an accelerometer would be sensitive enough. One of the problems is that large quakes can saturate the system very easily. The 6.7 LA quake in January saturated my system and LA is 500km (300m) away. The ideal station would have a set of high sensitivity sensors and a set of strong motion sensors. Maybe someday... >If I can monitor, I would want to digitize the signal(s) from the sensor >to 8 or 10 bits depending on micro controller, is this good enuf? You really need 12 or more bits, 8 or 10 bits will also cause saturation problems. There are plenty of 12 bit A to D cards out there that work with the software on the PSN BBS's that most stations run to collect the data. >What is the typical sampling rate? Anywhere from 30 to 100 samples per second. QUESTION regarding earthquake recordings Date: Wed, 13 Sep 95 08:56:49 PDT Does anyone know if there is a ftp site where I can download some latest earthquake recordings? I am interested in actual acceleration vs. time charts/graphs. Answer 1: You can get seismic waveforms from IRIS: telnet dmc.iris.washington.edu and log on as "bulletin" with password "board". Go to main menu and select SPYDER. This has traces of all large earthquakes in the past few years. However, they are not acceleration vs time but are typically velocity or displacement vs time. You can also access SPYDER from the WWW: http://www.iris.washington.edu -- Alan Jones Note: WinQuake version 1.8 and higher will display SAC binary files available on the dmc system. - Larry C Answer 2 Also check www.seismicnet.com via ftp or www. -- Ken From: Andrew Papanikolas, University of Arizona Department of Geosciences The University of Arizona Department of Geosciences has WWW site which may be of interest to the readers of this group. Highlights include real-time display of the vertical component of the UA/IRIS broadband station TUC, the ability to "make your own seismogram" by selecting a time frame and station components, seismograms of past events, and a world map of recent global seismicity. You can also meet the faculty and students of the U of A geophysics group. Access this site through the URL: http://www.geo.arizona.edu/saso andrewp@............................ Andrew Papanikolas at University of Arizona From KN: This site is also the source of a .gif file that allows the viewer to see the data from the IRIS broadband sensor that monitors frequencies between .01 Hz and 20 Hz. The data is updated every 5 minutes. Check out http://www.geo.arizona.edu/saso/latest.gif ___________________________________________________________________________ In 1994, a company in Pasadena offered off the shelf amateur seismograph packages that included software, hardware and sensor . For info contact: GeoSense Inc, 115 W. California Blvd #304, Pasadena, CA 91105. (818) 727-8939. Add a PC and you're ready to go. I haven't seen the unit in operation so I can't comment about its performance. I contacted the manufacturer and learned that their software will not allow individuals to share data with the PSN format. that may or may not be a consideration. ___________________________________________________________________________ ___ EARTHQUAKE DATA, Where to find it: The finger servers provide information for earthquakes greater than M2.0 from these internet locations. Command Line: Locations: finger quake@............................ & Central Calif. finger quake@........................... Calif. finger spyder@.............................. Motion Events, Worldwide finger quake@.......................... finger quake@........................ Central Region database finger quake@.......................... Idaho, Wyoming, Montana finger quake@.......................... of Nevada, Reno finger quake@.................................. Oregon finger quake@..................................... USA finger quake@.............................. USA finger quake@.......................... Islands finger quake@........................ Bay Area Events recorded on PSN amateur equipment finger quake@.................... Madrid Seismic Network finger solar@.................. Observatory World Wide Web sites: http://ui.nmh.ac.uk/ (BGS -Global Seismology Info) http://www.geo.ed.ac.uk/quakes/quakes.html. http://www.geophys.washington.edu/seismosurfing.html http://quake.wr.usgs.gov http://garlock.wr.usgs.gov/pub/CURRENT/norcal.list http://www.geo.arizona.edu/saso http://www.seismicnet.com (for the PSN homepage) http://www.eas.slu.edu/index.html USENET NEWSGROUPS: ca.earthquakes sci.geo.earthquakes sci.geo.geology Mailing Lists: QUAKE-L Subscribe from LISTSERV@............. This list advises of recent earthquakes and includes discussions from people working in the field of seismology. ----- PSN-L Subscribe from listserver@.............. This mailing list is dedicated to the exchange of information on homebuilt seismographs and other earthquake related information. ----- ___________________________________________________________________________ Recently, the USGS has provided PSN with additional data for earthquakes with magnitudes below the M2.0 cutoff. Events below the finger server threshold are usually not felt and therefore do not stimulate much public interest. Smaller events ARE of interest to the community of seismology `buffs' who see the events on their homebuilt instruments. This data is currently available only for the Northern and Central California Seismic Network thru the courtesy of the USGS in Menlo Park. You may access it via FTP or from either the San Jose PSN BBS. The Internet FTP address is: andreas.wr.usgs.gov Login: ftp Password: (your :Login address) cd pub/psn/summarys get lst3days.rpt The file, LST3DAYS.RPT, contains the data for events greater than M0.1 for the previous 72 hours. It is updated hourly. However, the data is *uncorrected*. It is right off the automated computers and therefore should be considered PRELIMINARY. The data for the larger events may be revised after they are manually checked and timed. Another site for similar data for smaller earthquakes can be found at http://garlock.wr.usgs.gov/pub/CURRENT/norcal.list ___________________________________________________________________________ ___ >>>> Additional Files: Some Informational Files via FTP.andreas.wr.usgs.gov/pub/psn or PSN BBS: Filename Size Available Description ------------------------------------------------------------------------------ EMONPKG.ZIP ******* SDRXX.ZIP ******* Seismic Data Recorder W162vXXX.ZIP ******* WinQuake 16 bit version for Windows 3.1 WQ32V21.zip ******* WinQuake 32 bit version for Windows 95 and NT SEISINFO.ZIP 40960 02/16/92 | Collected info-LP seismograph construction LEMANSEI.ZIP 307,584 12/28/94 | Lehmann seismograph design art work in | GIF format PENDULUM.ZIP 1,792 12/28/94 | Details on the design of a pendulum | mass weight and period PSNSEIM.DOC 56,064 12/28/94 | Document to be used with data | collection code and seismograph SEISAMP.GIF 106,624 12/28/94 | GIF file of a seismic amp design used | by PSN members TELEMETRY.DOC | Monitoring Times article RE: Seismic | Telemetry ___________________________________________________________________________ Larry Cochrane has added some new files in his FTP directory at www.seismicnet.com They include seismograms from amateur sensors as well as the seismograms telemetered to the USGS in Menlo Park from various remote locations by VHF radio links. (Also available are SDR, WINQUAKE, and the new version of WINQUAKE called WQ32V23.ZIP for Win95/NT) Currently, data is automatically available for download from the Mt. Mocho site above San Jose, Ca. (*.CMM), from Mt. San Bruno south of San Francisco (*JSB), and from Garin Park near Hayward, Ca. (*.CGP) immediately after an event occurs. You will need a copy of WINQUAKE to view the data files. Finger quake@................... to see what new files are available for downloading. The subdirectories are arranged by date (YrMo). Select the directory then "dir" for a listing of available files. Files extensions describe the location of the sensor. ___________________________________________________________________________ From Mike Martin regarding commercial sensors Larry I just read a reply to Tim regarding seismographs, and one of the questions was about commercial seismographs. A company you didn't list that I got my seismograph from is Wards Natural Science Establishment out of Rochester, NY. 1-800-962-2660. It is a long period horizontal, and can be set up either N-S or E-W. It runs with a strip recorder that the paper needs to be changed every 125 hours. It moves 1 foot per hour. It runs for about $2300.99 with all the extras. Advantages: 1. Naturally, a long period seismograph is very sensitive, and can pick up quakes from very distant places. I live in Central California (Porterville for those of you on the west coast), and I ahve picked up quakes from South America (October 2, 1995), the Mexico quakes from the past month, and the M8.2 in Japan last October (1994). 2. As a science teacher, having anything at all is wonderful. My students ask every day about earthquakes, and living in California doesn't disappoint. Disadvantages: 1. Paper costs 35 bucks for 8 rolls (about 6 weeks worth). 2. Exchanging quakes is impossible unless you have a flatbed scanner and can send PICT files over the Net. 3. It is slow: 2 mm every 24 seconds. It doesn't show a good differentiation of P and S arrivals. 4. Cost - 2300 bucks is alot when there are other options out there. But, in 1990 when I got this, ti was the best available to teachers. Good hunting! Mike Martin Porterville High School Porterville, CA 209-783-2311 email - 74653.536@.............. ___________________________________________________________________________ Disclaimer: The views expressed are solely those of the writer and do not necessarily represent those few fortunate enough to (still) be employed in the field of seismology. A warning label should also be attached to the effect that amateur seismolgy can be harmful to the pocket book and to interpersonal relationships due to the awe, frustration, and enjoyment that can result from the fanatic pursuit of watching "Mother Nature" change the face of our planet. Regards to all and special thanks to all the contributors, especially to Ted Blank, Larry Cochrane, and Alan Jones who've provided us with the tools to actively pursue our hobby with the fervor (obsession) that it deserves! One final note of thanks to Dr. Lucy Jones at USGS at California Institute of Technology for summing up this most appropriate defination of an earthquake: "An earthquake is the way the Earth relieves its stress by transferring it to the people who live on it." Ken Navarre (Seismoholic) Updated by Larry Cochrane 11/28/99