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30 years after the Loma Prieta earthquake

30 years after the Loma Prieta earthquake

Reflecting on the 30th anniversary of Loma Prieta this week, earthquake experts recently shared their perspectives on how the event impacted them, the Bay Area and the research community at large.
October 17, 2019

On Oct. 17, 1989, destruction from the Loma Prieta earthquake killed 67 people and injured 3,757. The magnitude 6.9 quake went down in the history of California’s central coast as the most damaging seismic event since 1906. It sent seismic waves from its origin in the Santa Cruz Mountains to San Francisco, the East Bay and beyond. The 20 seconds of shaking knocked down part of the Bay Bridge, collapsed a section of freeway in Oakland and caused more than $5 billion in damages.

Anne Kiremidjian, a professor of civil and environmental engineering, remembers exactly what she was doing 30 years ago when the shaker struck. She was driving in Los Altos southeast of Stanford’s campus around 5 p.m. “As the aftershocks were coming it was amazing to see the cars across from me on Foothill Expressway heave up and then down and, as the seismic wave rolled across, the cars on our side did the same,” said Kiremidjian, who studies the intensity and duration of ground shaking during a quake and estimates the probable structural damage. On the Farm, library collections fell over like dominoes and huge pieces of concrete were shaken from the facades of old buildings. More than 200 campus structures were damaged, some beyond repair. That night, 1,600 students were displaced from their residences.

Loma Prieta caused an underground rift along 22 miles, mostly on a previously unknown fault, whereas the 1906 quake occurred along the San Andreas Fault and ruptured about 300 miles of Northern California with an estimated magnitude of 7.9. But Loma Prieta impacted a larger population and more buildings – and it served as a much-needed wake-up call to residents, city planners, engineers and geophysicists. According to the U.S. Geological Survey, there is a 72 percent likelihood of at least one earthquake of magnitude 6.7 or greater striking somewhere in the San Francisco Bay region before 2043.

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