Pre-Quake Shake

IRFAN KHAN/LA TIMES VIA GETTY IMAGES

AFTERSHOCK: A librarian surveys the mess after a big earthquake shook California this past July.

Earthquakes usually strike without warning. But scientists recently discovered that a sequence of small tremors may foretell a larger quake, days or even weeks in advance.

Scientists at Los Alamos National Laboratory in New Mexico compiled a detailed record of earthquakes in Southern California from 2008 to 2017. They found that 72 percent of the quakes were preceded by clusters of foreshocks. Only extremely sensitive equipment can detect these tiny tremors.

This minor shaking might eventually help scientists more accurately predict larger earthquakes, says Wendy Bohon, a geologist at Incorporated Research Institutions for Seismology in Washington, D.C.

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