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@netcom.com)
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 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 @22.50 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@seismicnet.com (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
(also check Larry's FTP site at 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.
Th¤£öÃeal 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@deep-thought.geo.Arizona.edu
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@andreas.wr.usgs.gov Northern & Central Calif.
finger quake@scec2.caltech.edu Southern Calif.
finger spyder@dmc.iris.washington.edu Strong Motion Events, Worldwide
finger quake@giseis.alaska.edu Alaska
finger quake@gldfs.cr.usgs.gov USGS, Central Region database
finger quake@eqinfo.seis.utah.edu Utah, Idaho, Wyoming, Montana
finger quake@seismo.unr.edu University of Nevada, Reno
finger quake@geophys.washington.edu Washington, Oregon
finger quake@lamont.ldgo.columbia.edu Northeastern USA
finger quake@vtso.geol.vt.edu Southeastern USA
finger quake@tako.wr.usgs.gov Hawaiian Islands
finger quake@sys5.seismicnet.com S.F. Bay Area Events recorded
on PSN amateur equipment
finger quake@eas.eas.slu.edu New Madrid Seismic Network
finger solar@drao.nrc.ca Solar Observatory
World Wide Web sites:
ui.nmh.ac.uk (BGS -Global Seismology Info)
ww.geo.ed.ac.uk/quakes/quakes.html
www.geophys.washington.edu/seismosurfing.html
quake.wr.usgs.gov
garlock.wr.usgs.gov/pub/CURRENT/norcal.list
www.geo.arizona.edu/saso
www.seismicnet.com (for the PSN homepage)
www.eas.slu.edu/index.html
USENET NEWSGROUPS:
ca.earthquakes
sci.geo.earthquakes
sci.geo.geology
Mailing Lists:
QUAKE-L
Subscribe from LISTSERV@VM1.NODAK.EDU
This list advises of recent earthquakes and includes discussions
from people working in the field of seismology.
-----
PSN-L
Subscribe from listserver@seismicnet.com
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
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@sys5.seismicnet.com 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@compuserve.com
___________________________________________________________________________
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