The movie San Andreas, which depicted back-to-back earthquakes hitting Los Angeles and San Francisco, provided a chuckle for seasoned seismologists. In the film, the biggest temblor measures 9.6, a tsunami crests over the Golden Gate Bridge, and skyscrapers knock together like children's toys. Not that we admit to actually watching the thing.
Retired U.S. Geological Survey seismologist Lucy Jones said the story covered “fantasy territory.” But a new analysis of the damage possible in a worst-case-scenario earthquake is pretty eye-opening. Under one scenario, the state wouldn't necessarily split from here to the Bay Area, but millions of homes would be damaged and destroyed.
A new California Earthquake Risk Analysis report from CoreLogic, the Southern California real estate data firm behind oft-quoted monthly sales reports, essentially translates the latest USGS Uniform California Earthquake Rupture Forecast for the Golden State into home value. A longer fault rupture from SoCal to the Bay is now possible under an 8.3 magnitude scenario along the San Andreas Fault, according to the USGS, and that could result in 2.3 million to 3.5 million damaged homes, CoreLogic found.
For comparison, the city of Los Angeles has about 3.9 million people, most sharing homes. Damage to homes statewide could amount to $289 billion, the risk report found.
Because the analysis is based on a newer rupture forecast, that damage amount is as much as 111 percent more than the last report, based on a years-old USGS forecast, the real estate firm stated. The “increase in damaged homes” compared with the prior USGS forecast would “primarily” affect those in Southern California, the analysis states — the result of a fault rupture “extending nearly the full length of the San Andreas Fault, from Mendocino County to Riverside County.”
An 8.3 magnitude quake that shatters the San Andreas up and down the state might be farfetched, but a earthquake with a magnitude 6.7 or greater is long overdue. “California has always been at high risk for earthquakes,” according to the CoreLogic report, “but this risk may have a greater impact than previously anticipated.”
Federal earthquake experts, however, are hedging their bets.
“Because of a lack of consensus on how to forecast earthquakes, it is important that our model adequately portray epistemic uncertainties, which represent our incomplete understanding of how the earthquake system works,” according to the Uniform California Earthquake Rupture Forecast.