The San Francisco Bay Area is ripe for a major earthquake, and it could strike as early as next year, experts announced yesterday.
The "most dangerous urban fault in America," scientists say, is the Hayward Fault, which runs under densely populated areas in the Bay Area including the city of Oakland (see map of California).
The past five major earthquakes along the fault have occurred at regular 140-year intervals. The last one, in 1868, was mostly forgotten in the aftermath of the ruinous 1906 quake, which was triggered by the nearby San Andreas Fault.
(See a photo gallery of San Francisco after the 1906 quake and today.)
But the 1868 event has garnered more distinction recently: October 2008 will mark the 140th anniversary of that magnitude 7 quake.
"We don't know when the next big quake [will be], but we do know that the Hayward Fault is ready," Tom Brocher, a seismologist with the U.S. Geological Survey (USGS), told National Geographic News.
New research also suggests the Hayward is much longer than previously believed, which could portend a disastrous earthquake two to four times bigger than was once thought.
"It's going to be right in Oakland," Brocher said of the quake's likely epicenter. "The shaking is going to be much stronger and much more damaging."
Predicting the Big One
Scientists are now scrambling to predict when the next big one will hit.
USGS geophysicist Fred Pollitz has developed a prediction model by studying active Bay Area faults that move at regular intervals.
By studying the recurrence of events and the rates of creep—continuous, tiny movements of faults that don't cause earthquakes—Pollitz has concluded that the probability of a quake along the Hayward fault in the next 30 years is 45 to 75 percent.
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