San Andreas fault Geological fault line extending more than 965km (600mi) through California. It lies on the boundary between the North American and the Eastern Pacific plates of the Earth's crust. Plate tectonic movement causes several thousand earthquakes each year, although only a few are significant. San Francisco lies close to the fault line, and is prone to earthquake damage. The most destructive earthquake occurred in 1906, when it horizontally displaced land around the fault by up to 6.4m (21ft) and killed 503 people. Notable tremors also occurred in 1989 and 1994.

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San Andreas fault a fault line extending through the length of coastal California. Seismic activity is common along its course and is due to two crustal plates sliding past each other along the line of the fault. The city of San Francisco lies close to the fault, and such movement caused the devastating earthquake of 1906 and a further convulsion in 1989.