Expert Sees 90% Chance of Big Bay Area Quake by 2020

The chance of a major earthquake in the San Francisco Bay Area by 2020 has climbed to near certain, according to a scientist who warns that new faults were found after the devastating 1989 Loma Prieta quake.

“A 90% likelihood is probably not unreasonable,” David Schwartz, a seismologist for the U.S. Geological Survey, told a conference on earthquake hazards.

Four years ago the agency forecast a 67% chance of a killer quake by 2020.

But since the October, 1989, quake, researchers have found new faults or suspected faults, including two in the southern half of San Francisco Bay that run under or close to San Francisco International Airport, Candlestick Park and the San Mateo Bridge.

The Oct. 17, 1989, earthquake had a magnitude of 7.0, killed 63 people and caused more than $6 billion in damage.

“Significant new information has been obtained on the behavior and location of faults in the region,” Schwartz told a San Francisco conference on seismic hazards this week.

Growing evidence indicates that some Bay Area faults are potentially deadlier than anyone guessed four years ago. Researchers also found that some faults are slipping faster than originally suspected.

The researchers used sonar-like devices on boats to map hidden faults beneath the bay and detonated explosives to map faults under hills and valleys. Other tools included instruments that measured the millimeter-by-millimeter creep of faults.