...like California? - China is relaxing its one-child policy for victims of the May 12 earthquake, which killed more than 65,000 people, many of them children. Close to 25,000 people are still missing. And a new study shows that large earthquakes routinely trigger smaller quakes worldwide, including on the opposite side of the planet, even in areas that do not usually have earthquakes.
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. Scientists previously noted that three major quakes triggered not only nearby aftershocks, but small quakes at great distances. For instance, after the devastating 2004 Sumatra earthquake, quakes even occurred in Ecuador, on the opposite side of the earth.
Seismologist Kris Pankow says, "Previously it was thought seismically active regions or geothermal areas were most vulnerable to large earthquake triggers." But Pankow and colleagues analyzed 15 major earthquakes stronger than magnitude-7.0 since 1992, and found that at least 12 of them triggered small quakes hundreds and even thousands of miles away. Is California next? Keep an eye on the frogs. Our readers report that linear clouds, which are another sign of an impending earthquake, have been sighted in Seattle and northern California on May 20 and 21.
Art credit: Aaron Velasco, University of Texas at El Paso.
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