SALT LAKE CITY - Until 1992, when California's magnitude-7.3 Landers earthquake set off small jolts as far away as Yellowstone National Park, scientists did not believe large earthquakes sparked smaller tremors at distant locations. Now, a definitive study shows large earthquakes routinely trigger smaller jolts worldwide, including on the opposite side of the planet and in areas not prone to quakes.
"Previously it was thought seismically active regions or geothermal areas were most vulnerable to large earthquake triggers," says Kris Pankow, a seismologist at the University of Utah Seismograph Stations and a co-author of the new study.
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| ©Aaron Velasco, University of Texas at El Paso
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| This map of the world shows seismic stations that detected more than twice the normal number of small, nearby earthquakes after the passage of what are known as "surface waves" from major quakes that were centered hundreds to thousands of miles away and occurred from 1992 through 2006. A new study co-authored by University of Utah seismologist Kris Pankow found that at least 12 of the 15 major earthquakes (greater than magnitude-7) during 1992-2006 triggered small quakes in distant parts of the world. Scientists once believed big quakes could not trigger distant tremors.
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