Wednesday, February 4, 2009

Did construction of a new reservoir...

and its subsequent filling with water cause the devastating M7.9 earthquake in China on 12 May 2008 where ~70,000 people died? Some scientists certainly believe so, especially because of the close proximity of the reservoir to the fault, and that such a large magnitude event hasn't occurred at this location in centuries. I don't believe in coincidences either, and other earthquakes have been attributed to dam projects elsewhere. However, in this case, I remain skeptical.

A simple quantitative analysis of the circumstances of this tremor leads me to doubt that crustal loading was indeed the cause. I calculated the additional weight of the water relative to the weight of the column of crustal rocks to the 19 km depth of the focus. The added weight of the impounded water contributed only 0.3% of the total mass of the underlying rocks, which, in my opinion, is an insignificant load. Perhaps other factors were at work, say, increased pore fluid pressures that may have "lubricated" the fault plane?

Shameless self-promotion: if you are interested in hazardous Earth processes then you should consider enrolling in my GEOL 360 course during spring term.

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