Hayward Fault may give us next quake

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While San Francisco is likely to be hit by a catastrophic earthquake within the next 30 years, its starting point is likely to be across the East Bay on the Hayward Fault, according to seismologists.

When studying fault lines, scientists look at how frequently earthquakes of a certain magnitude “repeat” themselves on each line.

According to these studies, San Francisco is not expected to face an earthquake like the one that ravaged The City in 1906, rupturing from the San Andreas Fault, for another 100 years or more, scientists from the United States Geological Survey say.

“A repeat of the 1906 earthquake is not real likely, there are many other earthquakes I think we're far more concerned about, particularly on the East Bay faults,” said Mary Lou Zoback, a USGS senior scientist. “We've done a study on the Hayward Fault and the average is 150 years for a repeat and the last one was 1868, so we're very close.”

Known as the “Great San Francisco Earthquake” until 1906 because it caused damage on both sides of the Bay, the 1868 earthquake on the Hayward Fault had a 7.0 magnitude and resulted in the deaths of five people, injuries to dozens more and property damage in excess of $300,000 in 1868 dollars.

Due to increased population and building, a Hayward repeat is expected to wreck more havoc than its predecessor. Anticipated to have a 6.9 magnitude, it would cause 500-plus deaths, destroy 5,800 buildings, damage some 227,000 others, push 450,000 people into homelessness and result in $23 billion in damage, according to USGS estimates.

Although a Hayward earthquake would not affect San Francisco as severely as places in the East Bay, The City will still be “really hard hit and damaged,” according to Tom Brocher, another USGS seismologist, who is based in Menlo Park.

Buildings around San Francisco’s shorelines, where there is landfill, will be particularly vulnerable.

“All the ports, docks, the Marina, Mission Bay, a lot of the Financial District — that part of town will really get shaken,” said Brocher, who said a Hayward earthquake would hit San Francisco harder than the 1989 Loma Prieta earthquake.

Nonetheless, many San Franciscans seem to be putting off any worries about earthquakes for another day, said Connie Halog, a volunteer for California's Office of Emergency Services. Halog spent Sunday and Monday staffing a booth about putting together 72 hours of emergency preparations at a commemorative earthquake expo presented by The San Francisco Fire Department Historical Society.

“People say they know it’s going to happen, but it’s easier to put it off until tomorrow,” Halog said.

San Francisco resident Glenn Mogel, visiting the expo with his 4-year-old daughter, said he and his wife have stocked up several days worth of food and water, as well as added extra seismic strengthening to their Mount Davidson home.

“I don't know if you can be ready enough,” Mogel said. “I'd like to think things are built [better] and it wouldn’t be totally destroyed.”

Robert Dreschler, a San Francisco native, said he hoped past history would determine the future of his Eureka Valley home, built in 1896.

“I've been through two of them [earthquakes, in 1957 and 1989],” said Dreschler. “You can only do so much, then fate takes over.”

beslinger@examiner.com

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