The Western portion of California is an area which experiences frequent and strong earthquakes due to the interactions between the two tectonic plates. Earthquakes are vibrations in the earth produced by a rapid release of energy, such as a sudden slip on a fault. This movement occurs along faults, mainly the San Andreas Fault. The San Andreas Fault system is the major fault system found in California. Fault systems running parallel to the San Andreas include the San Jacinto, Elsinore and Imperial.
Faults are breaks in rock masses along which movement has occurred.
A fault zone can be identified by a band of crushed rock. The length of a fault may vary from a few centimeters to thousands of kilometers. The Pacific Plate moves Northwest relative to the North American Plate at approximately the same rate that your fingernails grow. So, in 10 million years, San Diego will be located approximately where we now find Santa Barbara. This slip can be released in the form of a larger, infrequent earthquake.