Dams and Earthquakes

China’s earthquake and early warning system

(May 13, 2009) The Chinese government has announced it is installing an experimental earthquake early warning system, capable of sending warnings within seconds before a quake strikes.

The fully functional system, though years away, is meant to give residents a few seconds, or minutes, to take cover so to speak.

The plan, issued the day before the highly charged 1st anniversary of the Sichuan earthquake, which killed close to 90,000 people, was released by China’s State Council in a white paper, called “China’s Actions for Disaster Prevention and Reduction.”

According to the state news agency, Xihuanet, the system will be “three-dimensional” involving monitoring on land, in the ocean and on the ocean-bed, and in the space-air-ground observation.

Some 937 fixed seismic stations, more than 1,000 mobile seismic stations, and 1,300 earthquake precursor observation stations have already been built, enabling quasi-real-time monitoring of quakes above 3.0 on the Richter scale. A mobile observation network of more than 4,000 mobile observation stations is up and running, a high-speed seismic data network of 700 information nodes has been built, and a text message service to provide prompt earthquake reporting has been launched.

But what will become of all these seismic readings that the hardware is meant to generate? The experience with last year’s earthquake doesn’t bode well.

Last year, in the months prior to the May 12, 2008 earthquake, when the reservoir level of the Zipingpu dam, just miles from the earthquakes’ eventual epicentre, was in rapid drawdown, a flurry of foreshocks were measured around the Zipingpu dam. Fan Xiao, chief engineer of the Regional Geology Investigation Team of the Sichuan Geology and Mineral Bureau called the “swarm” of 200 small earthquakes, including five bigger than magnitude 3 during the evening of February 14, “spectacular.” Many scientists think that the Zipingpu dam’s location and its drawdown triggered what is called “reservoir induced seismicity” (RIS). So far, over 90 cases of RIS have been reported around the world. Earthquakes are thought to be “triggered” by fluctuations in the reservoir level, by the weight of the reservoir, when the “stress field” is perturbed by the reservoir, and when water infiltrates the rock and propagates the “pore pressure.”

Those same scientists are desperate to see the detailed seismological measurements to fully understand the dynamic role that Zipingpu’s reservoir had in last May’s deadly earthquake. So far, the Sichuan Seismological Bureau has refused to release that data.

Why? Because with clear scientific evidence that the Zipingpu dam triggered last year’s deadly quake, public pressure to abandon the rash of large dam building in the seismically active southwest part of China would become intense.

So, seismological data, as it turns out, can cause seismic political shifts. I expect that Chinese officials will think twice before they hit the “disclosure” button and Chinese lives will continue to be at risk.

Patricia Adams, Probe International, May 13, 2009

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