China’s May 12 earthquake raises risk along nearby faults

September 11th, 2008 - 4:25 pm ICT by IANS  

Beijing, Sep 11 (DPA) The devastating 8.0-magnitude earthquake in southwest China’s Wenchuan county has increased the risk of major quakes along nearby geological fault lines, a group of international experts has said in a report.Using computer modelling, the geophysicists found that “geological stress has significantly increased on three major fault systems in the region,” said the report in Geophysical Research Letters, published by the American Geophysical Union.

The researchers calculated changes in stress along the Xianshuihe, Kunlun, and Minjiang faults, which are 150 km to 450 km from the Longmenshan fault that caused the earthquake in Wenchuan May 12.

They concluded that the Longmenshan quake had doubled the probability of major earthquakes on the other three fault lines to between 57 percent and 71 percent for a quake of at least 6 on the Richter scale in the next 10 years.

The team, led by Shinji Toda of the Geological Survey of Japan, estimated the chances of a quake of magnitude 7 or higher at 8-12 percent in the next decade and 23-31 per cent over the next 30 years.

“One great earthquake seems to make the next one more likely, not less,” researcher Ross Stein of the US Geological Survey said in a statement.

“We tend to think of earthquakes as relieving stress on a fault. That may be true for the one that ruptured, but not for the adjacent faults,” Ross said.

Another team member, Jian Lin of the Woods Hole Oceanographic Institution, urged the Chinese government to step up education in earthquake risks and improve building quality in areas near the three fault lines on the eastern Tibetan Plateau.

“There needs to be widespread education in earthquake preparedness, as well as systematic inspection of buildings in these regions of heightened risk,” Lin said.

“Every new building inspection and evacuation plan could potentially save lives.”

Chinese government officials and scientists were “carefully examining the paper in detail”, the report said.

“We hope the long-term forecasting allows the Chinese government to make it a priority to mitigate future damage,” Toda said.

“We recommend that Chinese scientists carefully observe changes in seismicity by installing new seismometers in the region.”

The Wenchuan earthquake killed at least 70,000 people, with some 18,000 people still listed as missing.

Thousands of aftershocks have shaken the area since May, including two 6.1- and 5.6-magnitude quakes at the southern end of the Longmenshan fault that killed at least 38 people in the last two days of August.

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