Expecting the Big One

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THOUGH it can offer scant comfort to the victims of the earthquake in Haiti, seismology is making some slight progress in its search for the holy grail of being able to predict dreadful events like that on Tuesday. New studies into ultra-slow-motion events deep underground called nonvolcanic tremors are showing vague but promising signs that the same kind of subterranean danger signals that allow us today to forecast when a volcano is about to erupt may one day offer some warning of the hitherto unpredictable nucleation — the explosive beginning — of an earthquake.

The most interesting studies are those that are proceeding, slowly and expensively, in Parkfield, Calif. (as it happens, just a little north of the road crossing where James Dean was killed in a traffic accident nearly 55 years ago). A deep hole has been drilled into the countryside there, directly into the San Andreas fault, which runs for 800 miles along the junction between the North American and Pacific tectonic plates.

The academic and government researchers who run the drilling program seek to find out what happens at the precise point of contact between two plates. It now appears highly likely that the very low impact, but still measurable, nonvolcanic tremors that the researchers have detected in boreholes deep beneath the San Andreas are in some way associated with the destructive earthquakes that occur at shallower depths above them. What the scientists would still like to determine is whether it might be possible to discern a nonvolcanic tremor’s signature in the deep crust some useful time before a major earthquake happens far above.

This is highly relevant to the disaster in Haiti because the Enriquillo-Plantain Garden fault, the tectonic culprit behind Tuesday’s earthquake, shares many similarities with the San Andreas: it is a strike-slip fault of about half the length (it runs from the Dominican Republic to Jamaica), it separates two plates (the North American and the Caribbean), for most of its length it is simultaneously locked solid and under severe stress, and it shears substantially every century or so. (The last time was in 1907, in Jamaica; scientists have long warned of a catastrophe — one day — involving Port-au-Prince.)

http://www.nytimes.com/2010/01/15/opinion/15winchester.html?th&emc=th