February 5, 2009

Man-Made Dam May Have Caused Massive Earthquake In China

While some believe China's devastating magnitude 7.9 earthquake last year was caused by natural occurrences, some government officials and scientists have blamed a man made dam.

The quake, which occurred in the Sichuan province, was China's worst in a generation, causing 70,000 deaths and leaving 5 million homeless.

Now some scientists are claiming that the quake was the result of excess pressure on a fault line caused by Zipingpu dam.

The 511-foot-high dam's reservoir, which lies 550 yards from the fault line, was drained as a result of the quake.

"I'm not saying the earthquake would not have happened without the dam, but the presence of the massive Zipingpu dam may have changed the size or time of the quake, thus creating a more violent quake," Fan Xiao, a chief engineer at the Sichuan Geology and Mineral Bureau, told the AP on Wednesday.

Scientists call the phenomenon "reservoir induced seismicity," which has caused several small quakes in the past, including a magnitude-6.4 quake near India's Koyna dam killed at least 180 people in 1967.  However, no quake linked to reservoir activity has been as large as the Sichuan quake.

Fan told AFP on Thursday that Zipingpu's location was an important factor, as was the fact that the huge tremor happened at a key moment for the reservoir when its water level was falling at a rapid pace.

"The Zipingpu reservoir was built right on the earthquake fault area, so it was very easy for Zipingpu to have had an impact on the fault," Fan said.

"The most dangerous period (for reservoir-induced quakes) is after the water level in a reservoir has reached its highest point, and it changes and starts going down."

"And Zipingpu's water level started to change and go down rapidly just before the earthquake happened," he added.

Fan and other experts who believe the quake was caused by the dam published their opinions in last month's issue of Science magazine.

The Chinese government maintains that the Sichuan quake was an unavoidable natural disaster.

Lei Xinglin, a geophysicist at the government's China Earthquake Administration, argues that while reservoirs increase seismic activity, they will not cause an earthquake.

"A reservoir in the region will have positive and negative effects on a potential earthquake, but it is ridiculous to say an earthquake was caused by the dam," Lei told the AP.

"In order to gain more knowledge, we still need to carefully research this topic rather than jumping to conclusions."

Pan Jiazheng, a well-known hydraulic engineer involved in the Three Gorges Dam project, also rejected the theory in an article published by Science Times, a Chinese magazine, in December.

"There has never before been a case of a reservoir triggering an 8.0-magnitude earthquake in the world," Pan wrote.


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