The San Andreas Fault is a 750-mile-long right-lateral strike-slip transform fault in California that forms the tectonic boundary between the Pacific and North American plates, sliding at an average rate of 20 to 35 millimeters per year and divided into three main segments with varying earthquake risk. Identified by Professor Andrew Lawson in 1895 and confirmed as the source of the devastating 1906 San Francisco earthquake, the fault was actually named after the San Andreas Valley, not the nearby lake—a common misconception. Spanning from the Mendocino Triple junction offshore to the Salton Sea in the south, the fault transitions into a rifting boundary where sediment from the Colorado River prevents the trough from filling with seawater. In 1953, geologist Thomas Dibblee proved the fault had experienced hundreds of miles of lateral movement, while the SAFOD project (2004-2007) near Parkfield drilled directly into the fault to study its deep behavior. The southern section's "Big Bend" acts as a restraining bend that locks the fault, producing a Southern California earthquake-recurrence interval of roughly 140–160 years. This massive structure remains one of the most studied earthquake systems in the world, posing a continuous threat to the region's large population centers.