San Francisco Earthquake October 17, 1989 and its aftermath. The largest to hit the San Francisco area since 1906 and registering a 7.1 magnitude, the earthquake's effects are shown in stores, and on the street. California Highway Patrol's response to, and findings of, the seismic shaking on the San Francisco-Oakland Bay Bridge and the Cypress Street Viaduct. Scenes show difficult rescue attempts and earthquake victim evacuations.