San Francisco’s big seismic gamble

[...] San Francisco lives with the certainty that the Big One will come. But the city is also putting up taller and taller buildings clustered closer and closer together because of the state’s severe housing shortage. Now those competing pressures have prompted an anxious rethinking of building regulations. Experts are sending this message: The building code does not protect cities from earthquakes nearly as much as you might think.

It’s been over a century — Wednesday marks the 112th anniversary — since the last devastating earthquake and subsequent inferno razed San Francisco. Witnesses on the morning of April 18, 1906, described the city’s streets as rising and falling like a ribbon carried by the wind.

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California has strict building requirements to protect schools and hospitals from a major earthquake. But not skyscrapers. A five-story building has the same strength requirements as a 50-story building.

Yet skyscrapers cast a much broader shadow of risk across a city and their collapse or impairment could cause a cascade of consequences.

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