Experts Say Next Quake Could Wreak Havoc
By Carol Dimmick
Within the next 30 years the odds are that a major earthquake will strike the Bay Area and destroy thousands of homes in the Richmond and Sunset districts, according to a report commissioned by the SF Department of Building Inspection.
A year-long study by The Applied Technology Council of Redwood City paints a grim picture for west side residential neighborhoods, where it estimates that 11,000 buildings in the Sunset and more than 4,000 in the Richmond could be destroyed if a 7.9 earthquake occurs along the San Andreas Fault.
The report, which studied the effects of four major earthquake scenarios on privately owned buildings throughout the City, was undertaken by the SF Department of Building Inspection after the U.S. Geological Survey announced a more than 60 percent likelihood that a major earthquake will hit the Bay Area within the next three decades.
What is unique about this report is that it layers a lot of different information to predict where and how much loss will occur on a neighborhood-by-neighborhood basis.
According to computer models used in the study, the Sunset could lose as much as 41 percent of its privately owned buildings and the Richmond 35 percent in a major earthquake because of the vulnerability of its older housing stock of wooden, single-family homes and apartment buildings.
Ned Feenie, an architect who served on the panel of experts that put the study together, said the Richmond and Sunset districts are prime targets for the next big earthquake because of their "soft story" construction and sandy soils.
"In the Richmond and Sunset districts you have the perfect storm scenario for a major disaster," he said.
The study found that a major earthquake could have a devastating effect on the city's affordable housing stock. If a 7.2 magnitude quake were to occur along the San Andreas Fault, the City could lose 3,461 units of below-market-rate housing. One-third of those housing units, or 1,210 units, would be lost from the Richmond and Sunset districts.
The total economic loss from a major earthquake could reach $13.7 billion citywide. For Sunset property owners it could mean losses of more than $2 billion. Estimates for the Richmond are put at just over $1 billion.
Depending on the magnitude of the event and time of day, the report says hundreds of west side residents will need temporary housing and many will require hospitalization for injuries. Estimates of deaths and injuries vary depending on specific circumstances.
The grim picture came as a surprise to a panel of experts, who point to wood frame "soft story" construction in both districts and liquefied soil in the Sunset as the culprits.
The report says soft story buildings are particularly vulnerable because they are weaker and more flexible in a horizontal direction due to garage or extensive window openings at ground level.
"Until this report, we weren't even thinking about the residential areas of the Sunset and Richmond districts," said Patrick Buscovich, a structural engineer who served on a Building Inspection advisory panel, in an article published in the SF Chronicle.
Supervisor to Hold Hearings on Report
The report's predictions of building damage, death and economic losses have caught the attention of Supervisors Jake McGoldrick and Fiona Ma.
Ma, who is co-chair of the City Services Committee, expressed concern after reading the report.
"I am holding a hearing to discuss its impacts on July, 8 at 9:30 a.m., at City Hall, Room 263. The Sunset has a great number of wood frame buildings and I want to get some good ideas from the experts," she said.
Ma says she is looking for mitigation measures that could include ways to reduce the amount of non-shear walls, and may even consider new legislation requiring homeowners to retrofit their home if funding can be found.
McGoldrick also favors hearing from the experts before making any recommendations, although he expressed a preference for an outreach program to educate residents. McGoldrick, like Ma, wants to provide financial assistance to encourage homeowners to retrofit their homes.
City Unable to Use $315 Million in Bond Money
When the Loma Prieta Earthquake hit the Bay Area in 1989, voters approved $350 million in earthquake safety bonds after banks were reluctant to make loans for retrofitting buildings.
Several years later, after the economy rebounded, property owners were able to get loans at more favorable rates from private lenders and the City was left sitting on $315 million in earthquake safety bonds.
Wayne Lawrence, program administrator for the city's Unreinforced Masonry Buildings Seismic Safety Loan Program, says limits placed on the funds that restrict its use for commercial buildings or buildings with four of more units, combined with lower interest rates from private lenders, made the bond money unattractive to borrowers.
"We overestimated the need," he said.