One thousand dead, $54 billion in property damage, a $15 billion hit to business and 85,000 housing units lost. That is the grim scenario facing San Francisco if privately owned buildings are not seismically retrofitted to withstand the violent earthshaking of the next big temblor, according to a recent analysis.
Faced with the large number of fatalities and dire economic consequences, city officials are examining ways to require owners of earthquake-vulnerable buildings to upgrade their properties to survive the violent earthshaking.
“The life losses that we are projecting vary from a low of about 70 in a magnitude-6.9 earthquake on the Hayward fault to nearly 1,000 if it occurs during the day with a magnitude of 7 on the San Andreas [fault],” Tom Tobin, a consultant with The City’s Community Action Plan for Seismic Safety project, said during a recent Building Inspection Commission meeting.
“The concrete buildings built before about 1980 is a source of about 50 percent of the casualties,” Tobin said. That’s followed by residential soft-story buildings at 31 percent. Those are wood-framed buildings where the first story is weaker than the above stories, so they can lean or collapse as a result of an earthquake.
Last year, The City adopted a voluntary program to encourage private-property owners to retrofit soft-story buildings with five or more units by waiving some fees. Those types of buildings account for about one-third of the projected 85,000 housing units that would be lost. Three- or four-unit soft-story buildings comprise another one-third.
Also, The City is asking voters to approve Proposition A on Nov. 2. The earthquake retrofit bond would authorize the borrowing of $46.1 million in loans or grants to pay for the seismic retrofitting of 125 government-funded affordable-housing soft-story buildings and 31 single-room-occupancy buildings.
In addition to collapsed buildings and lost lives, ensuring that San Francisco can swiftly recover following a major earthquake, that residents can remain at home amid rebuilding efforts, and ensuring that food services for those in need continue uninterrupted are among the challenges.
The Community Action Plan for Seismic Safety has spent several years examining San Francisco’s earthquake vulnerabilities and plans to issue a final report by Dec. 31 with recommendations for making buildings seismically sound. Under consideration is a deadline for private-property owners to do the work, along with incentives.
Also, the plan will examine the losses San Francisco could face if fires flare up following the earthquake, and how to protect those buildings on “poor soil” found in the Marina district as well as parts of the Mission district and South of Market area.
“Effects on community character both physical and social are real, in terms of losses that we would expect and the disruption that would occur under present conditions would change this city dramatically,” Tobin said.
Pressure put on seismic work
City officials should ultimately establish a deadline for when private-property owners must have their buildings seismically retrofitted, according to one recommendation under consideration through San Francisco’s Community Action Plan for Seismic Safety project.
“We think fundamental to this is The City has to say this is important to us and establish that there is a deadline,” said Tom Tobin, a consultant for the project.
Before the deadline arrives, however, Tobin said other measures should first be established. That includes requiring retrofitting upon the point of sale.
“We know from experience from other programs statewide that not everybody will retrofit if it’s voluntarily,” Tobin said. “Doing it upon sale is a time when the cost could be rolled into the financing. Not that that is easy. That would make either owners lose value or it would make the building more expensive for the buyer.”
Such a mandate would impact about 1 to 2 percent of The City’s housing stock annually.
Seismic retrofitting of soft-story buildings cost about $16,000 per unit, according to a city controller’s report.
— Joshua Sabatini
Estimated losses in the event of a big earthquake:
Deaths: Up to 1,000
Housing units lost: 85,000
Cost to repair building damage: $17 billion to $54 billion
Business losses: $5 billion to $15 billion
Source: San Francisco’s Community Action Plan for Seismic Safety project, Oct. 7 presentation