A seismometer is a very sensitive instrument that can detect movements of the Earth's surface. The surface is in constant motion due to natural and man-made phenomena. For example, the solid Earth tide is the stretching of the Earth due to the gravitational pull of the moon. Phoenix, Arizona slowly rises and falls twice a day about 40 cm due to the moon orbiting overhead. Mining explosions in Morenci, Arizona create seismic waves which shake Phoenix daily. The amplitude of these vibrations are less than a micrometer and the oscillations have a frequency of several Hz.
The wide variety of ground motion, both in terms of period of oscillation and amplitude of vibration make it impossible for a single seismometer to record all types of motion. The AS-1 seismometer is a simple inertial system that can detect local mining explosions as well as moderate or large earthquakes that occur globally.
The seismometer is called inertial because it is based on Newton's 1st Law: A body at rest will remain at rest. In the AS-1 seismometer a magnet is suspended by a spring from a boom. When the ground vibrates the boom moves, but the mass wants to remain at rest, so the spring is stretched. The relative motion between the boom and mass is proportional to the ground shaking and causes a tiny electric current to be generated that is sent to the seismograph to be converted into a seismogram. Unfortunately, the spring will eventually pull the mass, so the seismometer requires damping. Oil or a magnetic damping system is used to dampen the AS-1 Seismometer.
The AS-1 is a portable effective classroom tool for teaching about earthquakes and the instruments that record them. The AS-1 has been loaned to many teachers through the Seismographs in Schools program. The AS-1 electronics have recently been redesigned and production is currently underway!
The TC1 is a vertical seismometer with a natural period of approximately 1s. Open-source hardware – based on the arduino uno -- boosts the longer periods in its recordings, so that teleseismic earthquakes are routinely detected, in addition to regional seismic activity. All plans for the TC1 and the interface between sensor and computer are freely available online to build your own, but the TC1 can also be purchased as a kit. Further information is available at http://tc1seismometer.wordpress.com/
In the UK, the SEP seismometer system is a horizontal seismometer that uses electromagnetic induction to detect ground motion (velocity) and eddy current damping. These seismometers are available from MUTR.
Rockwave has designed their VS1 seismometer to be the most advanced instrument available for home and educational seismology. Install the VS1 in a corner of your garage or basement and you’ll soon be exploring those tiny movements of the ground that are caused by earthquakes around the globe. These seismometers are available from Rockwave.
The S102 is an inertial seismometer that measures ground motion with respect to an elastically suspended mass. These seismometers are available from Engineering Acoustics, Inc..
Vertical School Seismometer, available commercially from Ward's Natural Science.
The CMG-PEPPV records vertical ground motion. It is a complex and sensitive instrument that can record global earthquakes. Guralp seismometers are available from Guralp Systems.
There are opportunities to include seismology in the classroom with or without a physical seismometer. Check out our Instructional Resources page for more information!
Instruments can be purchsed from the suppliers listed above, and IRIS resources are here to help get you started!
IRIS plans to donate instruments again in the 2013/2014 school year to schools in the US. Apply to receive an AS-1 instrument and 2.5 day training from IRIS! The application period will open in early 2013 for our workshop and instrument distribution. The application will be available from this site.
Below is a collection of instructional videos that step through the assembly of the AS-1 educational seismometer, and highlight important features of the installation and operation of AmaSeis software.
Many schools send a new image of their AS-1 helicorder record every 10 minutes to the IRIS Real-Time Seismic Image Display webpage.
Comparing ones own record to others is a very good way to determine if a given signal is indeed an earthquake, as large events are always recorded by many stations. Variations in the background noise due to microseisms can also be monitored all across the country. And it is a wonderful way to share your seismometer images with the community in which you live.
IRIS is now using Fling as the software to enable this realtime sharing. We have found it to be relatively simple to setup, and easier to use than any previous software. Please download our Fling instructions. If you have any problems getting set up, please let us know at firstname.lastname@example.org
We are pleased to announce that the new AS-1 Seismometer Calibration and Tune-up kits are available at no charge! They are available to any school in the US that is registered in our database. Not in our database? Register now!
• Enter your contact/shipping information in the request form.
• Also, download the guide to accompany the kit.
This kit and guide includes equpiment and instructions to perform 9 tune-up procedures to use when you set up, move, or just want the best performance possible from your instrument. Additionally, the guide includes the equipment and instructions to perform 5 calibration procedures.
Please use this guide to perform baselines tests so that if you have problems later they can be used to help troubleshoot your seismometer.