China's Dams

Sichuan earthquake may be aftershock of 2008 killer quake: Chinese geologist

(April 22, 2013) China’s construction of huge dams increases the probability of earthquakes, Fan Xiao warns.

By Patricia Adams, Probe International

The magnitude-7 earthquake that rocked Lushan, Sichuan province on Saturday, killing 179 and leaving thousands injured and homeless, may be an aftershock of China’s deadly 2008 magnitude 8 earthquake.

The April 20 earthquake, says Fan Xiao, a Chinese geologist and chief engineer of the Regional Geological Survey Team of the Sichuan Geology and Mineral Bureau, occurred along the same Longmenshan Fault Belt and may have been part of the stress adjustment process in the aftermath of the quake that killed over 80,000 people in 2008, making “this region a more dangerous area after the May 2008 Wenchuan earthquake,” said Mr. Fan.

Indeed, the south-western region has been made more dangerous by the government’s frenetic dam-building along the great rivers of Sichuan-Yunnan in actively seismic zones, says Mr. Fan, who published a report last year on the Wenchuan earthquake. It found a “mounting body of evidence and analysis indicates that the magnitude-8 earthquake was triggered by the mass loading and increased pore pressure caused by the Zipingpu reservoir.”

All the more reason, says Mr. Fan that “studies be done to determine the extent to which the filling and drawdown of Zipingpu’s reservoir has had an impact on the stress adjustment and seismic activity of the Longmenshan Fault Zone in general, and on the latest Lushan earthquake in particular.”

Just a few weeks ago, Fan Xiao warned that construction of huge cascading dams, close together along the great rivers of Sichuan-Yunnan in seismic hazard zones, increases the probability that these dams will both induce and be damaged by seismic activity. He pointed out that the next 10 years represents an especially dangerous period since scientists have observed that reservoir-induced seismicity (RIS) is most likely to occur within the first few years after a dam is filled. Typically, it takes time for reservoir water to penetrate deep into seismic faults and fissures before it triggers seismic activity.

Meanwhile, Xinhua News Agency has reported that, according to the Water Resources Bureau of Sichuan Province, the April 20 Lushan earthquake has damaged 34 reservoirs, mainly in Ya’an, Chengdu, Meishan, Leshan, Liangshan and other cities and prefectures. Of the 34 reservoirs, 20 have suffered cracks on the top of the dam or on the dam slopes, 3 have leaked, 4 have sustained damage to the spillway or water distribution facilities, and 7 have suffered damage to the sluice gate room, management buildings and other buildings.

An earlier study published by Probe International also warned that the 130-plus large dams that China is building in its western region, an area of high seismicity, are vulnerable to earthquakes or could induce earthquakes. In a worst-case scenario, dams could collapse creating a tsunami that would wipe out everything in its path, including downstream dams, and cause untold loss of life and property.

For more background to this issue see:

Deadly earthquake in China may be aftershock of 2008 Wenchuan quake

On alert: RIS risk amid rash of earthquakes in China’s Sichuan-Yunnan region

Fan Xiao: Did the Zipingpu Dam Trigger China’s 2008 Earthquake? —The Scientific Case

Feverish Chinese dam building could trigger tsunami

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