Quakes far from tectonic plate boundaries may simply be aftershocks of ancient temblors
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.
Most large earthquakes occur along the edges of tectonic plates, where stress and strain accumulate as large masses of fractured crust jostle and scrape past each other. But major temblors can also strike fault zones in continental interiors thousands of ki