Research: Big quakes weaken faults far away

On the heels of two powerful earthquakes around the Pacific Ring of Fire, U.S. seismologist are reporting that major quakes can weaken distant faults in the Earth's crust and may boost chances of future tremors.

The scientists studied 22 years of data from a section of the San Andreas fault near Parkfield, Calif., a tiny town in a seismically active area. After the devastating December 2004 earthquake off Indonesia, which triggered a deadly tsunami, small earthquakes increased in 2005 and caused the San Andreas fault to slip slightly. Similar movement was detected after a magnitude 7.3 quake in the California desert in 1992.

The findings are reported in tomorrow's issue of the journal Nature.

Today's magnitude 7.6 Indonesian earthquake occurred along the same fault that ruptured in 2004, killing more than 230,000 people. Thousands remain buried under collapsed homes, schools, shops, hotels and at least one hospital on the island of Sumatra, and authorities say the death will soar.

In American Samoa, at least 119 people died in yesterday's magnitude 8 quake and the tsunamis it generated.

(Top: Quake damage in Padang, on the island of Sumatra. Photo by Fitra Yogi, AP. Bottom: Tsunami damage in Pago Pago, on American Samoa. Photo by Ausage Fausia of Samoa News, via AP.)

Posted by Michael Winter at 06:39 PM/ET, September 30, 2009 in Asia, Nation, Research, World

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