Seismometers vary from the simplest demonstration unit to complex and expensive professional instruments used in research. Most commercial seismometers cost more than $5000 per station to purchase and operational costs can exceed this each year. For amateur seismologists, teachers and school systems, this cost is relatively high compared to the cost of other equipment and hobbies. Hobbyists and teachers can make less expensive instruments, but it takes some effort to find plans that teachers and hobbyists can use as a basis for construction. In general, these homemade instruments require the learning of engineering details and considerable time to care for the recording of the instrument. This task is made more difficult by the lack of standards in recording. The object of this page is to document components that can be combined or used to record earthquakes. The emphasis is on the low-end of the cost scale, those instruments that a hobbyist, teacher or school system could afford. The literature is rich in examples of seismic recorders, but many of the older designs now have better solutions using more modern electronics and computers.

The list below is not complete, suggestions for inclusion should be sent to tim.long@eas.gatech.edu.

Demonstration Units

A demonstration unit is one that can be used on a desk in a classroom. The moving elements should be visible and the instrument should not be so delicate that it could easily be broken in handling.

1. Demonstration units are usually homemade and follow simple plans. Many can be found by a search on the web. These primarily rely on direct visual observation of movements that the student induces. However, more advanced models use a simple mechanical or electronic device to write a short record. They usually utilize oil for damping, the simplest approach, or a copper plate in a magnetic field, or a damping load resister on the sensing coil.

Horizontal Component Seismometers

The horizontal component seismometer is the most common and is most often constructed to behave like a swinging gate. Given the proper tilt and care to reduce friction, an appropriate long period can be obtained. The design is basically the same as the horizontal component of the long period World Wide Seismographic Station Network (WWSSN) instrument. George Averill (1995) describes one version of this in detail. (Averill, George E., (1995). Build your own seismograph, The Science Teacher, Vol. 63, No. 3., 48-52.). A simple version can be constructed out of PVC pipe. See also http://www.info2000.net/~aloomis/seismom.htm

Vertical Component Seismometers

1. The vertical component seismometer system uses a spring and magnet in a coil. Larry Braile [http://www.eas.purdue.edu/~braile/edumod/handseis/handseis.htm] has described a model that is easy to construct. The Georgia Tech MAE Center teacher's workshop constructed a vertical component instrument based on the principal of the gravity meter.
2. Seismographs constructed by amateurs and professionals. There are many examples of these instruments, usually one of a kind. For many, instructions for their construction are available on the web or in the literature. Few of these units have been customized for mass production. A good example is the STM-8 seismometer built by Sean Morrissey [http://www.eas.slu.edu/People/STMorrissey/index.html]
3. AS-1 seismometer is a commercial version of a homemade seismometer. It comes with a digitizer that uses filters to allow recording of long-period signals from what is essentially an oil-damped 1.0 Hz vertical geophone. Allan Jones had written AmaSeis software to continuously record data from this unit.
4. The nearly Professional units

   a) The PS-2 by GEOSense, in California, is appropriate for recording local earthquakes that are prevalent in California. [http://www.geosense.com/seismometers.html]

   b) The CHEAP SEIS system under development will offer near professional control on response and timing.

   C The EIA S-102 [http://www.eaiinfo.com/] seismometer is a feedback system using linear transformer, [$1600]. This unit has been adopted by the MichSeis educational program. [http://www.geo.lsa.umich.edu]

5. The professional units at low price end
6. GURALP PEPPV. Guralp Systems has many high-end seismic systems used in research. Their special edition PEPPV is a reasonably economical seismometer that can be use for research. It was one of the original educational seismometers in the PEPP program [about $2800 plus an old computer] [http://www.guralp.demon.co.uk/]
7. PMD systems are three-component systems that use a unique motion sensing technique The PMD is also one of the original educational seismometers In the PEPP program [about $4000] [http://home.att.net/~pmdsci/]
8. Teledyne Geosciences has developed new broad-band seismometers for recording earthquakes [$2000 + recording equipment] [http://www.geoinstr.com/]
9. Professional quality instruments (typically more than $5000)
10. Sprengnether Instruments makes earthquake recording systems and seismometers. [http://www.sprengnether.com/]
11. Geo Space makes geophones and seismometers for many purposes. Their 1.0 Hz units are used extensively in short-period seismic stations. [http://www.geospacelp.com/]
12. Kinemetrics. Their 1.0 Ranger seismometer now comes in a broad band model appropriate for monitoring distant earthquakes. [http://www.kinemetrics.com/wr1.html]