1868 Hayward earthquake
|Date||October 21, 1868|
|Origin time||15:53 UTC |
|Areas affected||United States, California|
|Total damage||$350 million |
|Max. intensity||IX (Violent) |
The 1868 Hayward earthquake occurred in the San Francisco Bay Area, California, United States on October 21. With an estimated Richter magnitude of 6.8–7.0 and a maximum Mercalli intensity of IX (Violent), it was the most recent large earthquake to occur on the Hayward Fault Zone. It caused significant damage and a number of deaths throughout the region, and was known as the "Great San Francisco earthquake" prior to the 1906 San Francisco earthquake and fire.
The earthquake occurred at 7:53 a.m. on October 21, 1868. Its epicenter was likely located near Hayward, California, and its magnitude has been estimated to have been 6.8–7.0 on the Richter scale. At the surface, ground rupture was traced for 20 miles (32 km), from San Leandro to what is now the Warm Springs District in Fremont.
The town of Hayward experienced the most damage, with nearly every building destroyed or significantly damaged in the earthquake. The Alameda County Courthouse in San Leandro was destroyed, which resulted in the re-location of the County Seat to Oakland, its current site. The adobe chapel of Mission San José in what is now Fremont was also destroyed, as were several buildings in San Jose, San Francisco and throughout Alameda County. Damage was reported from Santa Rosa in the north to Gilroy and Santa Cruz in the south. Thirty deaths were attributed to the earthquake.
The United States Geological Survey estimates that Hayward experienced shaking measuring IX (Violent) on the modified Mercalli scale. San Leandro experienced shaking measuring VIII (Severe), while San Francisco and Oakland experienced shaking measuring VII (Very strong).
- Stover, C.W.; Coffman, J.L. (1993). Seismicity of the United States, 1568-1989 (Revised). U.S. Geological Survey professional paper 1527. United States Government Printing Office. pp. 73, 104.
- "Historic Earthquakes: Hayward, California, 1868 October 21 15:53 UTC". United States Geological Survey. 1993. Archived from the original on 5 November 2008. Retrieved 2008-10-15.
- The 1868 Hayward Earthquake: 139 years and counting... (press conference). Hayward Area Historical and Society Museum: U.S. Geological Survey, Association of Bay Area Governments, Hayward Area Historical and Society Museum, Vice Mayor-City of Hayward. 17 October 2007. Retrieved 15 October 2008.
- Aldrich, M. L.; Bolt, B. A.; Leviton, A. E.; Rodda, P. U. (1986), "The "Report" of the 1868 Haywards earthquake", Bulletin of the Seismological Society of America, Seismological Society of America, 76 (1): 71–76
- Boatwright, J.; Bundock, H., Modified Mercalli Intensity Maps for the 1868 Hayward Earthquake Plotted in ShakeMap Format, Open-File Report 2008-1121, United States Geological Survey