Seven years into Los Angeles’ landmark earthquake safety campaign, more than 8,000 seismically vulnerable buildings have been retrofitted across the city at an estimated cost of $1.3 billion, a new analysis shows.

The improvements mark the biggest advance in seismic upgrades in decades but still leave thousands of buildings vulnerable to damage or even collapse in a catastrophic temblor.

The regulations, a legacy of Mayor Eric Garcetti’s push for the nation’s most sweeping earthquake safety legislation, require a total of nearly 14,000 buildings to be retrofitted. The rules came after years of stalled efforts to improve the resilience of buildings despite growing evidence of earthquake threats.

The rules target apartments and other structures with soft, flimsy first floors as well as larger concrete-frame buildings of the type that sustained major damage during the 1971 Sylmar and 1994 Northridge quakes.

Many of the completed retrofits have come in wood-frame, soft-story apartment buildings, where upgrades are considerably cheaper than those in brittle concrete-frame buildings. Under the city’s rules, property owners pay for the structural improvements, but landlords can pass on a portion of the costs to tenants.

Earthquake experts have been pushing communities across California to focus on strengthening key infrastructure to better withstand big quakes, including utilities, water systems and buildings. Though L.A. has targeted thousands of structures, it still has not dealt with another type of vulnerable construction: steel-frame buildings, of which 25 were significantly damaged in the Northridge earthquake. That includes the Automobile Club of Southern California building in Santa Clarita, which came very close to collapsing.

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