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

In Southern California, two of the region's most important fault systems are the San Andreas Fault and the San Jacinto Fault.

From Science Daily • Jun. 18, 2026

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

Researchers based their conclusions on multiple core samples taken from a so-called “sag pond” along the San Andreas Fault, in the southeastern corner of San Luis Obispo County.

From Los Angeles Times • Jun. 2, 2024

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