Did Humans Help Cause the Great China Earthquake?

Feb 3, 2009 1:47pm

Earthquakes, whether you’re a believer or an actuary, are "acts of God."  We humans do not have the power to predict, stop, or cause them.  Or so we think.  We all jumped a bit at a headline in The Telegraph of London: "Chinese earthquake may have been man-made, say scientists." "An earthquake that killed at least 80,000 people in Sichuan last year may have been triggered by an enormous dam just miles from the epicentre," says Malcolm Moore’s article from Shanghai.  (See the full text HERE.) "The 511ft-high Zipingpu dam holds 315 million tonnes of water and lies just 550 yards from the fault line, and three miles from the epicentre, of the Sichuan earthquake. "Now scientists in China and the United States believe the weight of water, and the effect of it penetrating into the rock, could have affected the pressure on the fault line underneath, possibly unleashing a chain of ruptures that led to the quake. "Fan Xiao, the chief engineer of the Sichuan Geology and Mineral Bureau in Chengdu, said it was ‘very likely’ that the construction and filling of the reservoir in 2004 had led to the disaster." Huh?  We talked to a number of seismologists, and it turns out there is a lively debate going on in geology, with scientists believing that while the weight of a reservoir may not actually "cause" an earthquake, it may add to the stresses near a fault line, and hasten a quake that would have happened eventually.  "There have been some fairly large earthquakes that you can say were triggered by reservoirs around them, but proving this is not easy," says Leonardo Seeber of Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y.  In the case of last year’s China disaster, he says, "the conditions for the earthquake were there, and the trigger — the reservoir — is, shall we say, the straw that broke the camel’s back." The earthquake, in Sichuan Province in May, is estimated to have killed about 80,000 people and left five million homeless.  The region where it struck has been fairly quiet, but it is close to the line between tectonic plates where the Indian subcontinent is pushing northward into the rest of Asia. Christian Klose, a researcher at Columbia, made a presentation to the American Geophysical Union in December that in Sichuan, "The water volume amplified the strain energy on the Earth’s crust," relieving stresses in some places underground — but worsening it elsewhere.  His abstract is HERE.  Richard Kerr and Richard Stone, writing in the journal Science (their piece is HERE, but it’s subscription-only), say he is coy about his explosive subject; he never even mentions the dam.  But his colleagues know, and urge caution.  Paul Earle of the U.S. Geological Survey, in an e-mail to me, writes, "the only remote possible effect the dam had was to trigger the earthquake before it would have otherwise happened if the dam was not there. It is very difficult to make this connection and it remains rather speculative." Still, Seeber says there have been cases in the past where a reservoir provided a possible trigger for an earthquake, and in some, there’s no saying the quake would have happened any time soon without it.  Are we more powerful than we thought?  Seeber says it sometimes takes surprisingly little to upset the earth beneath us.

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