Giant Dam May Have Triggered Sichuan Quake

Shai Oster
Friday, February 6, 2009

Originally published in The Wall Street Journal 

BEIJING - Chinese and U.S. scientists are examining the possibility that a giant dam may have triggered the earthquake that killed some 80,000 people when it struck Sichuan province nine months ago, raising questions about ambitious dam-building projects across China's earthquake-prone western regions.

Pressure from the Zipingpu Dam, upriver from the town of Dujiangyan in Sichuan, may have helped trigger China's devastating earthquake in May 2008.

Scientists are looking into the likelihood that the weight of hundreds of millions of tons of water behind the Zipingpu Dam -- built only 500 meters from the earthquake's fault line and 5.5 kilometers away from the epicenter of the devastating May earthquake -- may have caused the 7.9 magnitude quake.

A research paper by a group of Chinese scientists concluded that the weight of water clearly affected seismic activity "and it is worthwhile to further study if the effect played a role in triggering the Wenchuan earthquake", according to an abstract of the paper published in the December issue of the Chinese journal "Geology and Seismology". The scientists were led by geologist Lei Xinglin a researcher at the Geological Survey of Japan and the Institute of Geology at the China Earthquake Administration.

"Science" magazine first reported on the debate in January.

Christian Klose, a researcher at Columbia University who has looked at man-made earthquakes, including those caused by mines or dams, has also looked into the causes of the Sichuan quake. In a presentation to the American Geophysical Union last year, he said the quake in a region that had been stable may have been set off by "local and abnormal mass imbalances on the surface of the Earth's crust," according to an abstract of that report. While not naming the Zipingpu dam, his talk noted that an extra 320 million tons of water accumulated two years before the quake on the upper Min River valley - the location of the Zipingpu dam. "The water volume amplified the strain on the Earth's crust," he said according to the abstract.

After the quake, there were fears that the 156-meter dam would collapse, but the reservoir was only half full at the time and it held.

Other Chinese scientists and the government have staunchly denied any connection between the dam and the quake.

"Nobody is claiming that there is direct proof that Zipingpu triggered the earthquake," said Peter Bosshard, policy director of environmental advocacy group International Rivers, which is a critic of many dam projects. "But there is disturbing scientific evidence based on the limited evidence available. That makes it all the more important that Chinese authorities make all the data available."

Dam-building is an especially sensitive topic in China, where the tangle of engineering and politics is epitomized by the Three Gorges Dam, by most measures the world's largest hydropower project. Some 1.4 million people had to be relocated to make way for the 400-mile long reservoir. Dams have been flashpoints for anger as relocated residents demand better compensation. Environmentalists say the projects needlessly damage the ecology.

Scientists caution that it's still far too early to say for certain that Zipingpu reservoir, which started filling in 2004 and had major fluctuations in the water level between 2007 and 2008, is the direct cause of the quake. But the debate could have an impact on plans to build even more dams in the area. A group of 62 Chinese environmentalists and scientists has already appealed for a moratorium on construction of new dams in the region pending further study of the risks.

China, the world's biggest dam builder, is eager to tap into a clean source of energy to fuel a growing economy now largely reliant on coal-fired power plants. China already has the world's largest hydropower capacity and is planning to double that capacity by 2020 -- the equivalent of adding another Three Gorges dam every two years, according to a recent report by the Asia Society and the Pew Center on Global Climate Change.

The most famous man-made earthquake was in India in 1967 when water behind the Koyna Dam set off a 6.3 magnitude quake that killed about 200 people. Even along China's Three Gorges Dam, a sacred cow for China's government, officials acknowledge that seismic activity has increased slightly since the 400-mile reservoir began filling eight years ago. But scientists rule out any connection between the Three Gorges Dam and the Wenchuan earthquake because the dam was too far away.