Dams and Earthquakes

Dam’s Role in Earthquake Revisited

(November 9, 2009) A recent scientific study adds to suggestions that a dam built near an underground geological fault line helped trigger the massive earthquake in Sichuan in May 2008 that killed more than 69,000 people and left almost 18,000 missing.

The study, published in late October in “Geophysical Research Letters,” and mentioned here (link to a Probe International story), suggests that the added weight of the Zipingpu Reservoir and dam likely helped trigger the 7.9 magnitude earthquake.

The dam “potentially hastened the occurrence of the Wenchuan earthquake by tens to hundreds of years,” wrote the report’s five authors. Wenchuan, a county in Sichuan, was the epicenter of the 2008 earthquake.

The study adds to the controversy over China’s massive dam-building program, which includes the flagship Three Gorges Dam, which forced the relocation of some 1.2 million residents. China’s biggest dam was not impacted by the May quake.

Critics say the dams are ecologically unsound white elephants. The government counters they provide much-needed clean energy and reduce reliance on dirty coal.

This latest study follows similar research by a group of Chinese scientists. “It is worthwhile to further study if the effect played a role” in triggering the quake, according to an abstract of the paper published in the December 2008 issue of the Chinese journal Geology and Seismology.

Chinese officials deny the reservoir, which was completed in 2005, had anything to do with the earthquake.

The authors of the latest study warn that there’s not enough data from before the dam was built to make a definitive correlation between the dam and increased seismic activity. “The microseismicity data recorded by the reservoir authority in the vicinity of the reservoir do not contain background data prior to 2004 or these data are currently unavailable to the public,” the authors explained.

There have been other concerns around the dam program. Influential business magazine Caijing reported this month that the threat of increasing landslides has forced managers of the Three Gorges dam to delay reaching the reservoir’s target height of 175 meters.

Ongoing droughts have further contributed to the Three Gorges problems. There’s less water than expected flowing into the reservoir, and officials have to release more to ensure sufficient water downstream.

Lower water cuts into two of the core justifications of the dam: electricity generation and shipping. Less water means the electricity turbines don’t operate at full capacity. Lower water also limits the size of boats that can travel on the reservoir.

(The Wall Street Journal reported about the geological risks of the dam in 2007. Government officials acknowledged those risks but said they had taken appropriate preventative actions.)

Shai Oster, Wall Street Journal, November 9, 2009

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