Zone of transform faults at the boundary between two tectonic plates in the western U.S. The fault runs along the coast of northern California for 650 mi (1,050 km) and passes seaward in the vicinity of San Francisco .
Movement along the fault is characterized by frequent earthquake s, including the major San Francisco quake of 1906, when parts of the fault line moved as much as 21 ft (6.4 m), and the less serious earthquake of 1989.