Which tectonic fault line is responsible for most of the major earthquakes in California?

The San Andreas Fault is the major tectonic fault line responsible for most of California's significant earthquakes. This extensive fracture in the Earth's crust stretches over 800 miles through western North America, marking the transform boundary between the Pacific and North American plates.12

Movement along the San Andreas Fault has caused numerous major earthquakes, including the devastating 1906 San Francisco earthquake and the 1994 Northridge earthquake, which occurred on a secondary fault. The fault's activity is a direct result of the Pacific plate sliding northward past the North American plate.13