Listening to the San Andreas

Discover what today's scientists are learning about the earthquakes to come

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  • Crystal Springs Reservoir marks the fault in California’s San Mateo County.

    Listening to the San Andreas

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Seismologist Mary Lou Zoback sometimes gives talks where she outlines all the good things the San Andreas has brought California. Gold. Oil. And a lovely, rumpled landscape.

The area around Parkfield, in southern Monterey County, shows these benefits. Its oak-dotted hills are genuinely beautiful. But no place reveals the frustrations of earthquake science more clearly.

In the 1980s, seismologists noticed that the San Andreas Fault beneath Parkfield possesses an unusual trait: It seemed to produce neatly timed 6.0 earthquakes about 20 years apart. Parkfield became to seismologists what Burning Man is to millennial revelers: a pilgrimage site that generated wild hopes. An expensive array of monitoring equipment was set up, a long-term forecast made: Parkfield would feel the next 6.0 quake in 1988.

That quake finally arrived in 2004.

"It certainly showed that earthquake prediction is not going to be easy," says Mark Zoback, professor of geophysics at Stanford University and USGS scientist Mary Lou Zoback's husband.

Still, Mark Zoback adds, the Parkfield project generated much useful data. And now he is heading a new project in the same vicinity: the San Andreas Fault Observatory at Depth. For the first time, scientists are drilling into an active fault zone: 10,000 feet "into an earthquake laboratory."

SAFOD researchers have retrieved core samples from the fault, and they've inserted seismometers deep into it as well. "They will tell us what's happening inside the fault before, during, and after quakes," says Mark Zoback. "That's never been done before."

And then? Like a lot of earth scientists, Mark Zoback is aware of the difficulties inherent in forecasting quakes: the unlikelihood that anytime soon we can turn on Channel 2 and hear, "Partly cloudy tomorrow, with a 90 percent chance of a 4.5 earthquake." The work at Parkfield reinforces the question: Is quake prediction even possible? "We just don't know," he says. "But I'm open-minded about it.

"People are not stupid. They know that if we could predict quakes, we could be a hell of a lot safer. Just because a problem is hard doesn't mean you shouldn't work on it."

Info: Visit http://quake.wr.usgs.gov to find out more about the San Andreas Fault and other quake research.

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