Magazine article Science News

Seismic Risk in Silicon Valley

Magazine article Science News

Seismic Risk in Silicon Valley

Article excerpt

Seismic risk in Silicon Valley

In the latest James Bond movie, the villain schemes to make a killing in integrated circuits by eliminating the competition clustered in northern California's Silicon Valley. His plan is to trigger a series of devastating earthquakes along the San Andreas fault, the sliding boundary between the American and Pacific plates that slices through the San Francisco peninsula.

Bond, of course, foils the plan. But had Agent 007 been reading the seismic literature he would have realized that he would be up against a more formidable foe: Mother Nature. In the last three years, seismologists have tagged a section of the San Andreas fault near Silicon Valley as the likely site of a moderate earthquake in the near future. And now, in the October GEOPHYSICAL RESEARCH LETTERS, Christopher H. Scholz argues that the magnitude and rupture length of this quake could be greater than has been previously suggested.

Scholz, a seismologist at the Lamont-Doherty Geological Observatory (LDGO) in Palisades, N.Y., focused his study on the region of Black Mountain, an 860-meterhigh formation located southwest of Palo Alto, Calif. Near Black Mountain, the San Andreas fault abruptly bends so that the 100-kilometer-long fault segment to the south of the mountain trends 9| more toward an east-west direction than do the segments lying to the north and south. Scholz believes that when the great 1906 earthquake struck San Francisco, the rupture propagated down the fault, crashed into this bend and dissipated much of its energy into Black Mountain. "The whole Black Mountain was uplifted and shattered during the earthquake,' he says. As a result, the fault along the segment to the south of Black Mountain slipped only about 1 to 1.4 meters, while the rupture caused a typical slippage of 2.5 to 4 meters on the fault to the north.

This difference in slippage over the two general regions has prompted a number of researchers to suggest that the southern segment is due for a quake. …

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