Earthquakes in San Francisco

San Francisco faces a very high earthquake risk, ranking among the most seismically hazardous major cities in the United States. The San Andreas Fault runs just offshore to the west of the city, while the equally dangerous Hayward Fault lies across the bay to the east, cutting through the densely populated East Bay. Together with the Rodgers Creek and Calaveras faults, this system makes a large quake almost a certainty over the coming decades. The U.S. Geological Survey has estimated roughly a 72 percent chance of a magnitude 6.7 or greater earthquake striking the wider Bay Area before 2043.

The city's history is defined by catastrophe. The great 1906 San Francisco earthquake, an estimated magnitude 7.9 rupture of the San Andreas Fault, and the fires that followed destroyed much of the city and killed roughly 3,000 people, making it one of the deadliest natural disasters in American history. In 1989 the magnitude 6.9 Loma Prieta earthquake struck during a World Series game, collapsing a section of the Bay Bridge and the Cypress Street freeway and killing 63 people. Since then the region has invested heavily in retrofitting bridges, hospitals, and older brick and soft-story buildings, and it uses the ShakeAlert warning system, but its position astride two major faults keeps the threat ever-present.