20 Years After Quake, Safety Renovations Continue

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UC Berkeley seismologist Peggy Hellweg still remembers what she was doing when the Loma Prieta earthquake struck 20 years ago this Saturday.

"I was looking over my son's shoulder and reviewing this essay that he had just finished editing on our Apple 2C," she said. "We felt the bump of the P-wave and ran out the door three feet away and into the yard. We watched the trees waving fantastically with no wind. It was exciting."

After the rumbling subsided, Hellweg's son returned to the computer, only to realize the power had gone out and his unsaved essay was gone.

But the essay was hardly the only thing damaged by the 6.9 magnitude temblor Oct. 17, 1989, which caused 63 deaths and nearly $6 billion in estimated damages to the Bay Area.

According to Stephen Mahin, director of UC Berkeley's Pacific Earthquake Engineering Research Center, technology has greatly improved since the quake, but there are still many unreliable structures built before safer building codes were established.

"Now we have to retrofit buildings that might be vulnerable," he said.

To address its seismic vulnerabilities, UC Berkeley has been retrofitting buildings since 1975.

In 1997, a structural engineering report found that 27 percent of the campus' square footage would perform either poorly or very poorly in a quake. Later that year, the campus launched the SAFER program, creating an

ongoing plan to improve the seismic safety of its facilities.

The campus has made significant progress, said Christine Shaff, spokesperson for facilities services.

"We have retrofit all of the buildings on the central campus that were rated very poor that are occupied," she said.

Shaff said most funding for retrofitting comes from the state, though the campus also received funds from the Federal Emergency Management Agency.

The campus uses a wide variety of retrofit methods, Shaff said. Hearst Memorial Mining Building, for example, uses an efficient-and more expensive-system called base isolation to protect against earthquake shaking.

Beyond the UC Berkeley campus, Bay Area cities have also been working to strengthen buildings.

David Bonowitz, a San Francisco-based structural engineer, said current vulnerable structures in Bay Area cities include unreinforced masonry-older red brick buildings-and soft-story wood-frame apartment buildings, which have parking garages or retail spaces on the ground floor that make the apartments likely to collapse.

Bonowitz said Berkeley has generally been ahead of the seismic safety curve.

"The big cities in the bay area, Oakland and San Francisco, are following Berkeley's lead," he said.

In order to mitigate future damage, Berkeley uses tax money to improve critical structures throughout the city, said Deputy Fire Chief Gil Dong.

"The city has taxed itself close to $400 million ... to retrofit schools, fire stations and our civic center," he said.

Dong also said the taxes funded past programs to fix unreinforced masonry and soft-story buildings.

According to a report by the Association of Bay Area Governments, Berkeley has the highest rate of adequately retrofitted homes-nearly 40 percent-in the Bay Area. Around 15 percent of homes are adequately retrofitted in Oakland and San Francisco. Furthermore, almost 80 percent of homes in Berkeley have been at least partially retrofitted.

Jeanne Perkins, a consultant for the association, said Berkeley's higher retrofit rate is largely due to the city's 1989 tax rebate program, which refunds up to a third of taxes assessed on a sold home to owners who properly retrofit their homes or apartment buildings.

However, Perkins said there is no guarantee that a retrofitted home will perform better in an earthquake.

"The California Earthquake Authority notes that it has never gotten proof that the losses will be reduced by more than 5 percent," she said in an e-mail, adding that an efficient retrofit on a home built before 1960 could create a ten-fold increase in the chance that it will be habitable after an earthquake.

Ultimately, retrofits in the Bay Area will be untested until the next major temblor. According to Hellweg, there is a 65 percent chance of a 6.7 magnitude temblor in the next 30 years.

When asked whether the Bay Area will be more prepared for a quake, Mahin simply replied, "I hope so."

Tags: EARTHQUAKE, LOMA PIETRA


Contact Michael Garcia at [email protected]



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