Rampant destruction, death if the Big One hits

Up to 800 people could die and 400 fires could ignite if the Hayward Fault were to rupture on Wednesday, a new report by the U.S. Geological Survey found.

The study, scheduled for release Wednesday afternoon at two events in Fremont and Berkeley, imagined a magnitude 7.0 tremor along the 52-mile fault line that stretches from San Pablo Bay in the north, to just east of San Jose in the south.

It would cause rippling calamities. Eighteen thousand people could be injured. The fires could engulf — and potentially consume — some 50,000 homes. Two thousand five hundred could be trapped in fallen buildings, and 22,000 could be stuck in broken elevators. East Bay residents might spend up to six months without water in the hardest-hit areas.

The prospect is in fact quite realistic. A previous report on the “Haywired scenario,” published last year, found there is a 72 percent chance of one or more magnitude 6.7 earthquakes occurring in the Bay Area before 2043.

“This is something that we consider to be a very plausible scenario,” said Ken Hudnut, science adviser for risk reduction at the U.S. Geological Survey and co-author of the new report.

Twelve earthquakes have jolted the Hayward Fault in the last 1,900 years, with an average recurrence interval of from 150 to 160 years, Hudnut said.

And 150 years have passed since the last one — a magnitude 6.8 — on Oct. 21, 1868. It shook a far different Bay Area: There were fewer people, structures and utilities to harm, notes the first Haywired report.

But even in that sparse landscape, buildings crumbled. A historic photograph from the Bancroft Library at UC Berkeley shows the Alameda County Courthouse in San Leandro with its top floors felled.

An earthquake of the same strength would do far more damage today.

“The Hayward Fault now threatens more than 7 million people, approximately 2 million buildings, the San Francisco Bay region’s and the nation’s economies, and dozens of major infrastructure lifelines including freeways and tunnels, pipelines, aqueducts, electric substations, electric transmission and distribution lines, phone lines and fiberoptic routes, and rail lines,” the report said.

It went on to note that the fault traces 300 homes and runs beneath Memorial Stadium at UC Berkeley, which recently underwent a massive seismic retrofit.

The Bay Area has invested tens of billions of dollars in earthquake protections since the magnitude 6.9 Loma Prieta earthquake rattled the San Andres Fault in 1989. The Bay Bridge now has a new eastern span and cities have upgraded brittle old concrete buildings that are most vulnerable to collapse.

But an earthquake on the “heavily urbanized” Hayward Fault would be more severe than Loma Prieta, which was “kind of off to the side” of the Bay Area’s major cities, Hudnut said. It could be far more destructive than its 1989 antecedent.

“This one would produce stronger shaking through a much larger part of the San Francisco Bay Area,” Hudnut said. “What we’re trying to convey here is that people should be ready.”