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

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

In 1812, a powerful quake — today, estimated at a magnitude of 7.5 and believed to have been caused by the San Andreas Fault — shook Southern California and immediately destroyed seven missions.

From Salon • Jan. 26, 2025

Such strike-slip faults are commonplace in the state, the most notable of which is the San Andreas Fault.

From Seattle Times • May 11, 2023

A large welcome sign planted directly on the San Andreas Fault proudly states: “The Lakes, Where Nature is Your Neighbor.”

From Los Angeles Times • Apr. 2, 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