Can Scientists Predict the Next Big Quake?

July 13, 2009 05:30 PM
by Sarah Amandolare
Seismic tools along the San Andreas Fault have detected a jump in tremors, bringing scientists closer to being able to predict future quakes.

A Tremulous Situation

In a study that used "[s]eismic tools buried in deep holes" nearly 200 miles south of San Jose, Calif., seismologists detected an 80 percent increase in the number of tremors in the San Andreas Fault over four years. Although it doesn't offer an exact prediction of the fault line's next rupture, the study could contribute to scientists' "long-sought goal of predicting potentially devastating quakes," according to Lisa M. Krieger of the San Jose Mercury News.

Tremors and quakes are quite different, Krieger explains. While earthquakes "are brief and fairly shallow events," tremors can last up to 21 minutes and occur up to 20 miles underground. The study also showed that tremors "are far more widespread than once thought," Krieger reported.

Led by Robert Nadeau, a seismologist at the University of California, Berkeley, and graduate student Aurelie Guilhem, the study also suggests that tremor activity has not lessened since significant quakes in the area in 2003 and 2004. According to Krieger, the continued tremors are "an indication that this stretch of the San Andreas Fault did not release stress, as once imagined, but instead has turned into a region of new stress and deformation."
Nadeau admitted that he is uncertain where tremors originate. According to Robert Sanders in an article for PhysOrg.com, some seismologists believe underground fluids cause tremors. Nadeau suggests otherwise: that tremors "are generated in a deep region of hot soft rock" that, when fractured, results in faint, rumbling tremors.

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Background: Earthquakes and their mechanisms

In "Nature Wages War: Earthquakes," learn what an earthquake is and what happens underground when one occurs. Explore the study of earthquakes and read about major earthquakes throughout history.

Reference: Earthquake activity in the U.S.; The San Andreas Fault

The U.S. Geological Survey provides regional maps of earthquake activity across the U.S. and the world.

Watch a Discovery Channel clip on YouTube that shows the San Andreas Fault up close and from a distance. The video also explains how tectonic plates along the fault line get "stuck," which can build tension and lead to earthquakes.

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