A coastal map including tectonic plate locations or fault-lines shows the tectonic plate boundaries in California. The coastline of California marks the border between the North American and Pacific plates.
The coastline of California lies between the North American plate and the Juan De Fuca plate. The Juan De Fuca plate is actually a small portion of the Pacific plate, which stretches from the western edge of the Americas to the eastern coastlines of Japan and Australia. The point at which the two plates meet is called the San Andreas Fault, which is responsible for much of the seismic activity in California.