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Feeling the Earth Move

July 1, 2007 By: Melanie Martella, Sensors Sensors


People have been trying to predict earthquakes for centuries—using animal behavior, weather, and seismic monitoring—but have had less than stellar success. As the human population shifts from a mostly rural existence to a mostly urban one, earthquakes exact a higher price, both in property damage and in lives lost.

CHALLENGE: Spot earthquakes before they happen

Click for larger image
Spectrogram of 2 hr. of data collected at the test site with the prototype E-sensors (Click image for larger version)

Recent research hints that low-frequency electromagnetic signals may presage an earthquake. If this is the case, detecting these earthquake precursors may provide a reliable early warning system. The theory goes something like this: as stress builds up around a fault in the Earth's upper crust, the ground around that fault emits low-level electromagnetic signals shortly before an earthquake occurs to relieve that pent-up stress. If you can reliably measure these signals you may be able to pinpoint when (and where) an earthquake is about to occur. The trick, of course, is to measure these small signals in the kinds of environments where earthquakes occur—and those are frequently rugged, cold, or otherwise tricky to instrument.

Quasar Federal Systems has developed compact, portable electric and magnetic field sensors that operate without mechanical or electrical contact with their surroundings and can withstand extreme environments. The sensors are sensitive enough to measure the possible earthquake-precursor low-frequency electromagnetic waves. The technology can measure static and dynamic stress in rock and boreholes and measures all six components of the magnetic and electric fields at low frequency. Integrated with DA hardware and GPS timing for real-time output, the system is in its final stages of data gathering and testing.

Contact Dr. Tom Nielson, Quasar Federal Systems, San Diego, CA; 858-228-3206, tom@quasarfs.com.






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