The fault was the cause of the 1906 San Francisco earthquake.It first appeared about 20 million years ago. The San Andreas Fault is the foremost of a set of faults along the boundary between the Pacific Plate on the west and the North American Plate on the east.
They happened on nearby major faults. The San Andreas is the stuff of nightmares because back on April 18, 1906, it caused the most catastrophic event in California history, the great San Francisco earthquake, which was so powerful that it caused a rupture in the land that stretched for 296 miles (477 kilometers).While its magnitude is uncertain, scientists have estimated that it may have been as large as 8.3. The forces associated with the fault have pushed up mountains in some places and stretched apart large basins in others. The San Fernando Earthquake (1971), the Northridge Earthquake (1994) and the Loma Prieta Earthquake (1989) did not take place on the San Andreas Fault (arguable in the case of the Loma Prieta Earthquake). The west side moves north, causing earthquakes with its movement. 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.
The San Andreas Fault is a right-moving ('dextral') strike-slip fault.It marks the boundary between the North American Plate on the east and the Pacific Plate on the west. San Francisco lies close to the fault line, and is prone to earthquake damage. Plate tectonic movement causes several thousand earthquakes each year, although only a few are significant. The SAF was rather casually named for San Andreas Lake (San Mateo County) sometime around 1906.