San Andreas Fault

The San Andreas Fault is a right-lateral geological fault that runs roughly northwest to southeast along the western coast of North America. This is a transform boundary between the Pacific Plate and the North American Plate. Many major earthquakes have been caused by slipping and ruptures of this fault.

Parkfield, California, a small town that lies on the fault, has been the location of several magnitude-6 quakes.

The San Andreas Fault has had three major earthquakes in the last 200 years:

• In 1857, 350 kilometers ruptured in Southern California. The approximate epicenter was Fort Tejon. Estimated magnitude = 7.9
• In 1906, 430 kilometers ruptured in Northern California, around San Francisco. The epicenter was near San Francisco. Approximately 3000 people died in the quake and subsequent fires. Estimated magnitude = 7.8 See: San Francisco earthquake of 1906.
• In 1989, 40 kilometers ruptured near Santa Cruz, California, causing 63 deaths. Estimated magnitude = 7.1. See: Loma Prieta earthquake.

See also:

• plate tectonics