Aftermath of the October 17, 1989 Loma Prieta Earthquake in Oakland, California. The highest concentration of fatalities, 42, occurred in the collapse of the Cypress Street Viaduct on the Nimitz Freeway (Interstate 880), where a double-decker portion of the freeway collapsed, crushing the cars on the lower deck. At a magnitude of 7.1, it was the worst earthquake in the San Francisco Bay Area since 1906.