The Loma Prieta earthquake struck at 5:04 p.m. as fans filled Candlestick Park for a World Series game between the San Francisco Giants and the Oakland Athletics, and viewers watching the pregame broadcast saw it cut out. The worst damage came where soft ground amplified the shaking: the upper deck of Oakland's Cypress Street Viaduct collapsed onto the lower one, a section of the Bay Bridge fell, and buildings in San Francisco's Marina District sank and burned.
The earthquake ruptured part of the San Andreas Fault System beneath The Forest of Nisene Marks State Park, about ten miles northeast of Santa Cruz, and took its name from nearby Loma Prieta peak. It measured 6.9 in moment magnitude, killed 63 people and injured 3,757. Santa Cruz County suffered heavy damage, but some of the worst destruction lay far to the north, where landfill and bay mud liquefied under the shaking.
In Oakland, the upper level of the double-deck Cypress Street Viaduct on the Nimitz Freeway collapsed onto the lower level, crushing cars and killing 42 people, the largest toll of the disaster. A 50-foot section of the San Francisco–Oakland Bay Bridge gave way, and one driver died. In San Francisco's Marina District, built largely on fill, houses slumped and fires broke out.
The timing may have saved lives. With the Bay Area's two teams meeting in the World Series, rush-hour traffic on the region's freeways was much lighter than normal. The series resumed ten days later, and the collapsed freeway and bridge span pushed California into a long and costly program of seismic retrofitting.