Bay Area Faults
The Hayward Fault
The Hayward Fault runs along the foot of the East Bay hills, something that all residents of the Bay Area, and the East Bay in particular, should know. Its last major earthquake occured on October 21st, 1868, destroying downtown Hayward, killing 5 people and, injuring 30. With an estimated magnitude of 6.8 it caused damage throughout the area. San Francisco alone suffered $350,000 in property damage. It was considered the "Great Earthquake" until 1906.
Scientists have been studying the past earthquakes on the Hayward fault. They have found that the most recent 5 major earthquakes happened on average every 140 years. Since it has been more than 144 years since the last major earthquake, the clock is ticking. It is very likely that the Hayward fault will rupture and produce a significant earthquake within the next 30 years.
The Hayward fault is not our only fault. It is a member of the San Andreas Fault system that runs from the Gulf of California in the south, to Cape Mendocino in the north. The San Andreas Fault system forms the boundary between the North American and the Pacific tectonic plates. In the Greater Bay Area, it San Andreas, which continues north up the peninsula, has several branches. Starting in the south near Hollister, the Calaveras Fault branches off to run east of San Jose and continue through Pleasanton and Danville toward Walnut Creek.
Please take some time to prepare yourself and your family in the unfortunate event of the 'Big One'. Click the 'Hazards and Preparedness' link at the top of the page for more information and great resources to help you.