List of earthquakes in California

Although the written history of California is not long, records of earthquakes exist that affected the Spanish missions that were constructed beginning in the late 18th century. Those records ceased when the missions were secularized in 1834, and from that point until the California Gold Rush in the 1840s, records were sparse. Other sources for the occurrence of earthquakes usually came from ship captains and other explorers. For the period 1850–2004, there was about one potentially damaging event per year on average, though many of these did not cause loss of life or property damage. The earliest known earthquake was documented in 1769 by the Spanish explorers and Catholic missionaries of the Portolá expedition as they traveled northward from San Diego along the Santa Ana River near the present site of Los Angeles.

The few damaging earthquakes that occurred in the American Midwest and the East Coast were well known (1755 Cape Ann, 1811–12 New Madrid, 1886 Charleston), and it became apparent to settlers that the earthquake hazard situation was much different in the West. While the 1812 Wrightwood, 1857 Fort Tejon, and 1872 Lone Pine shocks were only moderately destructive in mostly unpopulated areas, the 1868 Hayward event affected the thriving financial hub that is the San Francisco Bay Area, with damage from Santa Rosa in the north to Santa Cruz in the south. By this time, scientists were well aware of the threat, but seismology was still in its infancy. Reactions following destructive events in the late 19th and early 20th centuries included developers, press, and boosters minimizing and downplaying the risk out of fear that the ongoing economic boom would be negatively affected.

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