Earliest references to California earthquakes are contained in the records of the Missions, and diaries of priests and soldiers stationed in Alta California by the Mexican or Spanish governments.

Earthquake records became far more accurate with the arrival of Thomas Tennant in San Francisco during the Gold Rush. He kept weather observations and noted local earthquakes. Later, the U.S. Weather Bureau took over that duty. In addition, newspapers here generally printed one-line items about the smaller tremors; hence some of the data from the 1850-1890 era contain simple phrases such as “Earthquake felt here today,” or “An earthquake at 9 p.m.” Earthquakes mentioned in this online document with no locations listed were all felt in San Francisco, though the epicenters may not have been known.

Also invaluable for tracking earthquakes were various almanacs published in San Francisco and Oakland which kept day-by-day records of interesting or important occurrences.

Almost all data for the post-1900 era, concerning dates and locations, come from scientific publications, such as Holden’s catalogue of earthquakes, or records kept by Prof. Alexander McAdie of the Weather Bureau in San Francisco.

Information about the effects of those post-1900 earthquakes comes from diaries, newspapers, or other eyewitness accounts. Chabot Observatory in Oakland, Lick Observatory at Mt. Hamilton and the geology departments at Stanford and UC Berkeley were also invaluable in tracking earthquakes.

There are also two reports that are invaluable for the researcher: Toppozada, et al, California Division of Mines and Geology (CDMG) Open File report 81-11 SAC on Pre-1900 California Earthquakes, and USGS Professional Paper 1527 by Stover and Coffman on the Seismicity of the United States 1568-1989.

Historical information has been added to the 1865, 1868, 1906, 1957 and 1989 earthquake sections to give the reader the sense of the vast effects of major earthquakes.

Gladys Hansen
February 1996

There have been visitors to the earthquake chronology.