San Francisco works toward seismically retrofitting some concrete buildings

Amid collective anxiety about when the " Big One " will hit, San Francisco city officials are working to seismically retrofit the concrete buildings at risk of collapsing during a major earthquake .

Why it matters: Certain types of concrete buildings — ones that are inflexible or lack steel reinforcements — can be vulnerable to cracking and collapsing during a major quake, according to city officials .

Driving the news: Mayor London Breed on Tuesday directed San Francisco's Office of Resiliency and Capital Planning to draft legislation creating a screening process for concrete buildings to determine if they would be at risk during a quake.

• So far, San Francisco has a preliminary list of about 3,400 concrete buildings that could be at risk, the San Francisco Chronicle reports .
• But the city can't know for sure without speaking to building owners and doing proper inspections, Laurel Matthews, an earthquake resilience analyst for the city office told the Chronicle.
• Breed has also directed the Department of Building Inspection to create retrofit criteria for concrete buildings within the city's building code.

What they're saying: "San Francisco is always working to prepare for its next earthquake because for us it's not a matter of if, but when," Breed said in a press release.

Context: These efforts are part of the city's Earthquake Safety Implementation Program, a 30-year plan to improve seismic safety.

• In 2013, San Francisco introduced a program that has led to seismic retrofits of more than 4,500 multi-family residential buildings in the city, according to the mayor's office.

Threat level: There is at least a 95% chance of a damaging earthquake occurring in the San Francisco Bay Area within the next 100 years, the United States Geological Survey said in January.

• USGS defines that level of intensity as "felt by all, many frightened" with some heavy furniture moved, some instances of fallen plaster and slight damage.
• The USGS has alo determined that the Bay Area has a 72% chance of having a 6.7-magnitude or greater earthquake by 2043.

Flashback: The 1989 Loma Prieta earthquake was a magnitude-6.9 quake that caused extensive damage to parts of the Bay Area, resulting in dozens of deaths, thousands of injuries and billions of dollars in damage.

• The most powerful earthquake in Northern California's recorded history was in 1906, and ranged from a magnitude 7.7 to 8.3, according to USGS.

What's next: The resilency office and building inspection department must complete their respective tasks by Oct. 16, per the mayor's directive.

• But the entire process — from draft legislation to completion of seismic retrofits — is expected to be a lengthy one, the Chronicle reports, noting how past retrofits took seven years.

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