Small earthquakes may not predict larger ones

Quakes far from tectonic plate boundaries may simply be aftershocks of ancient temblors

12:52pm, November 4, 2009

Using the locations of moderate-sized quakes to estimate where “The Big One” will eventually strike may not work for all regions, a new study reveals.

Many researchers assume that small-scale seismic activity reveals where stress is building up in the Earth’s crust — stress that can cause larger quakes in the future, says Mian Liu, a geophysicist at the University of Missouri in Columbia. However, Liu and Seth Stein of Northwestern University in Evanston, Ill., report in the Nov. 5 Nature, many moderate-sized temblors that occur far from the edges of tectonic plates could be merely the aftershocks of larger quakes that occurred along the same faults decades or even centuries ago.

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