China's massive earthquake last spring left three major nearby fault lines twice as likely to produce strong quakes in coming years, according to a recent study.
The findings could help focus programs to reduce earthquake losses in areas where the risk is highest.
The May 12 quake struck with a magnitude of 7.9 in the Himalayan foothills of southwest China's Sichuan Province. It killed more than 69,000 people, and thousands more are still missing. (See photos of the devastation.)
That rupture relieved stress in the Longmen Shan fault, where it occurred, said study co-author Jian Lin, a geophysicist at the Woods Hole Oceanographic Institution in Massachusetts.
"Unfortunately, the same event now has transferred stresses to three other faults," Lin said. "As a result, all these three faults are even more dangerous than before."
The researchers say the chance of another strong earthquake—magnitude 6 or greater—striking the region in the next ten years may be as high as 71 percent. They also expect many smaller quakes along the faults with increased stress.
(Related: "Study Warned of China Quake Risk Nearly a Year Ago" [May 16, 2008].)
The findings were published this month in the journal Geophysical Research Letters.
Fault Webs
All the geologic faults in the Sichuan basin are the result of the Indian subcontinent wedging itself under the Eurasian tectonic plate in a collision that has been occurring for 50 million years. (Watch how the plates slammed together during the May 12 quake.)
The collision created the elevated Tibetan Plateau, as well as a complicated fault system throughout the region.
Lin and his colleagues used computer models to determine changes in stress along the Xianshuihe fault to the southwest of the May 12 quake, and the Kunlun and Min Jiang faults to the northwest.
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