Study: aseismic quakes may be precursors

July 5, 2006 at 4:05 PM
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STANFORD, Calif., July 5 (UPI) -- U.S. geoscientists are urging their colleagues around the world to search for evidence of tiny earthquakes in seismically active areas.

"In the last six years, there's been an explosion in research in what people are calling slow, silent or aseismic earthquakes," said Paul Segall, a Stanford University geophysics professor and lead author of a study concerning them. "In our paper, we describe four aseismic events that occurred on the Big Island of Hawaii. What made them interesting to us is when we realized that all four were associated

Unlike seismic earthquakes, which release sudden shock waves, silent temblors are too slow to cause ground shaking and, thus, are not considered hazardous. However, some researchers have speculated silent quakes may be precursors of mega-temblors that regularly occur in subduction zones where some of the world's biggest earthquakes have occurred.

"Silent earthquakes have recently been discovered in subduction zones in the Pacific Northwest, Japan, Mexico and elsewhere," Segall says. "It is likely that as these silent slow-slip events occur, the probability of a bigger seismic quake goes up."

The study appears in the journal Nature.

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