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SF Bay Area building demolition fuels quake study

By MIHIR ZAVERI
Associated Press

POSTED: 03:30 a.m. HST, Aug 17, 2013

HAYWARD, Calif. (AP) — Every time the ground trembles in the San Francisco Bay Area, people ask themselves: Could this be the big one?

For years now, the region has been bracing for a major earthquake that many worry could level vulnerable schools, hospitals and apartment buildings and unleash near-apocalyptic chaos. The U.S. Geological Survey estimates there is a 63 percent chance of a major earthquake in the region within the next three decades.

On Saturday, scientists hope to get one-up on the looming temblor, courtesy of the demolition of a university building.

Workers plan to implode the 13-story Warren Hall, a fixture of the East Bay hillside and of Cal State East Bay, which was built about 2000 feet from what researchers call one of the most dangerous fault lines in the country: the Hayward fault.

The building is expected to crumple into 12,500 tons of concrete and steel, which will slam against the ground sending out shockwaves similar to a magnitude-2.0 earthquake. Scientists have placed more than 600 seismographs in concentric circles within a mile of the building to pick up the vibrations.

USGS scientists hope the unique experiment will help map out where the ground might shake the most when the big one hits.

"We're just getting an idea of the distribution of the shaking," said Rufus Catchings, the lead USGS scientist on the project.

Many vividly remember the magnitude-6.9 Loma Prieta earthquake in 1989 that killed 63 people, injured almost 3,800, caused up to $10 billion damage, including a collapsed freeway that killed dozens of drivers. That quake was centered near Santa Cruz, about 50 miles south of here.

But in the East Bay, the Hayward fault — which runs through East Bay cities and under the University of California, Berkeley's football stadium — is the most likely to act up and cause a major earthquake in the next few decades, experts say.

The last major temblor on the Hayward fault was in 1868, Catchings said. He said the fault triggers a major earthquake every 140 years on average.

And it's not just the fault line residents have to worry about. Additional fault lines —called traces — split off from the main fault, and the location of many is unknown. The vibrations set off by Warren Hall's implosion will help scientists figure out where they are.

"In the event of a large earthquake, oftentimes it's not just one break in the ground, it's spread out over some distance," Catchings said. "You'd kind of like to know where all these things are if you really want to understand the hazard."

Mark Salinas, Hayward's mayor pro tem, said knowing where the ground shakes will help the city decide where to put new housing and other buildings. "This data, when it's available, will inform us on future development," he said.

The idea to use the building's demolition came from Luther Strayer, a geology professor at the university who called the USGS to see if they would be interested.

"Anybody in my position who is trained like I am would have recognized the opportunity," Strayer said. "That's really the cool part; it was sort of a simple obvious thing to do and it can do so much good for our society and the community."

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