Vulnerable city still in need of retrofit

Architectural professionals hope this month’s centennial of the 1906 Great Earthquake and Fire will make San Franciscans ask: Are we ready for the Big One?

Last month’s East Bay earthquakes served as small reminders we are in a vulnerable seismic zone. Experts say The City has made commendable progress on preparing for earthquakes but there is still significant work to be done.

Since the 1989 Loma Prieta earthquake, The City has focused on retrofitting buildings by type. The initial focus was on unreinforced masonry buildings, which, according to Fred Turner, a staff structural engineer for the California Seismic Safety Commission in Sacramento, are 73 percent retrofitted to date. The City has yet to specify which type of building it will focus on next, but structural engineers say unreinforced concrete buildings are the second largest threat.

“It’s important that The City and the building owners recognize that if they have a nonductile reinforced concrete building, that those buildings deserve review and having qualified professional engineers evaluate and assist the owners in developing strengthening schemes,” says Kurt R. Lindorfer, principal of Paradigm Structural Engineers Inc., San Francisco.

The silver lining, Lindorfer said, is that these buildings are typically built on relatively good soilmaking, them just a bit less vulnerable to quake damage. But Ron Hamburger, senior principal at Simpson Gumpertz & Heger Inc., San Francisco, and past president of the Structural Engineers Association of California and the National Council of Structural Engineering Association, said these structures, typically built in the 1920s and 1930s, are scattered throughout the city. He warned that buildings on corners and next to vacant lots are more vulnerable to earthquake damage.

“Buildings in the city tend to be leaned up against their neighbors and stabilize themselves,” Hamburger said. “It’s like a line of people. When something happens, the people at the end of the line will go flying.”

There are four seismic zones in the U.S., from 1 to 4, with 4 being the most dangerous. All the Bay Area and most of the state’s coastal areas are in Zone 4.

California law requires commer-cial property owners in Zone 4 to post placards if their buildings are not retrofitted according to code. Unfortunately, this is not strictly enforced.

“There is no law that requires a regulator to enforce the [placard] law so compliance is spotty at best and nonexistent typically,” Turner said. “It’s a lot like smoke detectors. You really should comply but no one really checks.”

Laurence Kornfield, chief building inspector for The City’s Department of Building Inspection, disagrees.

“I believe it is observed,” Kornfield said. “We are not actively in buildings looking for postings, but I’ve seen plenty around the city.”
Concerned San Franciscans should either look for compliance placards or ask building owners about the status of the building where they work and/or live. Owners should know what type of structure they own, but they may not necessarily know the condition of the building since California law does not require that commercial property sellers disclose earthquake weaknesses. Typically, the real estate industry polices itself around disclosure, but earthquake information is a bit thorny.

“If you’re selling a building and you’re by code required to upgrade and you haven’t, I think you’ve got to disclose that,” says Greg Shaughnessy, an attorney with Thelen Reid & Priest in San Francisco. “But if you didn’t, the seller could argue, ‘Why would I if I don’t have to?’ so to me, it’s arguable that it might not be actionable. It’s a gray area, but I would recommend to my clients that they disclose it.”

Building experts say they don’t want to scare San Franciscans about earthquake readiness but they do want to get the retrofit ball rolling a little faster, especially since the U.S. Geological Survey calculates a 70 percent chance of an earthquake with a magnitude of 6.7 or higher hitting the Bay Area within the next 30 years. “I think this discussion will come to the forefront, and I think you’ll see that a lot buildings haven’t been touched and a lot of realty is underutilized,” said architect Benito Olguin with BFHL Architects Inc., San Francisco. “At the very least, there will absolutely be a number of discussions.”

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