Petaluma, Bay Area prep for earthquake

The Association of Bay Area Governments recently shared a new tool that helps residents gauge how much earthquake damage they might incur if the “big one” hits, which experts project will happen sometime in the next 30 years.

Aptly called the Earthquake Home Safety Quiz, ABAG’s questionnaire allows residents to determine the resiliency of a single-family house, apartment or mobile home, and gain insight into seismic safety precautions they can take to prepare.

The quiz was deployed in the aftermath of ABAG’s updated housing loss estimates for the Bay Area. Since Petaluma is nestled between two of the most powerful fault lines in the region, with pitiable infrastructure and a large stock of old buildings, it’s vital to emphasize the importance of taking proactive measures, officials said.

“Petaluma did fairly well in the past … with earthquakes, but if there was one on the Rodgers Creek Fault, it could have a pretty significant effect here in Petaluma,” said Sonoma County Supervisor David Rabbitt, who also serves as ABAG president and is a member of the California Seismic Safety Commission.

An ancient fault runs under Petaluma, but it has long been inactive. To the west of the city is the San Andreas Fault and, to the east, is the aforementioned Rodgers Creek Fault, both seismically active.

If an earthquake with a magnitude of 6.7 or higher occurred on either - something the U.S. Geological Survey determined has a 72 percent chance regionally by 2043 – Petaluma would experience “very strong” shaking that could make a significant number of buildings uninhabitable.

According to the Modified Mercalli Intensity Scale, or MMI, most of the city scores an 8. When very strong shaking occurs, “nearly everything” is thrown down from shelves, cabinets and walls, and furniture gets overturned. Masonry buildings that are poorly constructed will suffer partial or full collapse, and even well-constructed buildings get damaged.

Multi-family, wood-frame buildings can partially collapse, and loose partition walls suffer damage that could cause them to fail. One- and two-story wood-frame homes shift if they’re not bolted to the foundation or be displaced and partially collapse if cripple walls aren’t braced. Certain pipes could break, too.

Some areas in the southeastern edge of the city have an MMI of 9, which coincides with “violent” shaking that would not only collapse poorly-constructed buildings, but even damage ones that are retrofitted.

Under the most dramatic scenario, ABAG projected as many as 2,400 residential buildings would be uninhabitable countywide if a magnitude 7.8 earthquake occurred on the San Andreas Fault. Damages would be upward of $710 million.

“We just need to be prepared and take steps to get us incrementally in the right places,” Rabbitt said.

The latest housing figures, while disturbing, were meant to kick start various disaster preparedness efforts in conjunction with the 10th annual Great California Shakeout on Oct. 18. Agencies and businesses statewide participated in earthquake drills and went over emergency procedures.

Public safety officials encourage residents to bolt or strap down moveable furniture, organize disaster supplies, and strengthen their home either physically or with insurance protections.

Self-reliance has become a common thread for elected officials hoping to encourage more personal onus in neighborhoods throughout the state. After last year’s deadly firestorm, the importance of disaster preparedness has never been more apparent.

“I think what we learned in the fires even is something we can pull into this,” Rabbitt said. “There’s a personal readiness (that’s required). You need to be able to survive on your own.”

(Contact News Editor Yousef Baig at yousef.baig@arguscourier.com or 776-8461, and on Twitter @YousefBaig.)