San Andreas Fault

American  

[san an-drey-uhs fawlt] / ˈsæn ænˈdreɪ əs ˈfɔlt /

noun

Geology.

1. an active strike-slip fault in the western United States, extending from San Francisco to southern California and forming the on-land portion of the western margin of the North American Plate.

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San Andreas Fault ¹ Cultural  

1. A fault in California where the North American and the Pacific tectonic plates meet and slide past each other. (See earthquake and plate tectonics.)

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San Andreas Fault ² Cultural  

1. A major geologic fault located in California. It runs from San Francisco to near San Diego and has been the source of serious earthquakes. (See also under “Earth Sciences.”)

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A major earthquake along this fault has been predicted for many years. Because California is densely populated, such an event might have very serious consequences.

Etymology

Origin of San Andreas Fault

First recorded in 1900–05; named after San Andreas Lake, located in the rift, in San Mateo County

Example Sentences

Monday evening’s earthquake was the second temblor of magnitude 3 or greater to occur near the San Andreas Fault on Friday.

From Los Angeles Times • Nov. 28, 2025

To the south, the Pacific and North American plates grind past each other along the San Andreas Fault, occasionally producing devastating earthquakes such as the 1906 San Francisco event.

From Science Daily • Oct. 22, 2025

The lake is situated atop the San Andreas Fault system, which creates substantial geothermal activity and an abundance of geothermal heat.

From Salon • Sep. 7, 2023

That’s why seismologists watch closely when swarms happen in this area, since the Salton Sea marks the end of the southern stretch of the San Andreas Fault.

From Seattle Times • May 30, 2023

The most common types of earthquakes are those where two plates meet, as in California along the San Andreas Fault.

From "A Short History of Nearly Everything" by Bill Bryson