2008-05-21

Could the Sichuan earthquake be a man-made disaster?

The following Scientic American article, published well before the deadly Sichuan earthquake, lists a whole range of environmental catastrophes the Three Gorges Dam is already causing and could cause in the future. One of them is major earthquakes.

China's Three Gorges Dam: An Environmental Catastrophe? (Mara Hvistendahl, Scientific American 25/3/08)

One of the greatest fears is that the [Three Gorges] dam may trigger severe earthquakes#, because the reservoir sits on two major faults: the Jiuwanxi and the Zigui–Badong. According to Fan*, changing the water level strains them. "When you alter the fault line's mechanical state," he says, "it can cause fault activity to intensify and induce earthquakes."

Engineers in China blame dams for at least 19 earthquakes over the past five decades, ranging from small tremors to one near Guangdong province's Xinfengjiang Dam in 1962 that registered magnitude 6.1 on the Richter scale—severe enough to topple houses.

Surveys show that the Three Gorges region may be next. Chinese Academy of Engineering scholar Li Wangping reports on the CTGPC's Web site that the area registered 822 tremors in the seven months after the September 2006 reservoir-level increase. So far, none have been severe enough to cause serious damage. But by 2009, the dam's water level is set to be raised to its full 575-foot capacity and then lowered about 100 feet (30 meters) during flood season. That increase in water pressure, in water fluctuation and in land covered by the reservoir, Fan says, makes for a "very large possibility" that the situation will worsen.

# Reservoir-induced seismicity.
* Fan Xiao is a geologist at the Bureau of Geological Exploration and Exploitation of Mineral Resources in Sichuan province.


- China's deadly earthquake: Was the Three Gorges reservoir a trigger? (Probe International, 14/5/08)
- China's quake: the dam factor (San Francisco Chronicle, 19/5/08)
- Induced seismicity (Wikipedia)
- Reservoir-induced Seismicity in China (L. Chen & P. Talwani, Pure and Applied Geophysics)