GEOLOGY

Detailed explanation-1: -The driving force of earthquakes in California is movement along the San Andreas Fault and the many associated faults within the San Andreas Fault System that form the tectonic boundary between the Pacific and North American tectonic plates.

Detailed explanation-2: -Tectonic plates move very slowly relative to each other, typically a few centimetres per year, but this still causes a huge amount of deformation at the plate boundaries, which in turn results in earthquakes.

Detailed explanation-3: -The San Andreas fault is the primary feature of the system and the longest fault in California, slicing through Los Angeles County along the north side of the San Gabriel Mountains. It can cause powerful earthquakes-as big as magnitude 8.

Detailed explanation-4: -The San Andreas fault line formed about 30 million years ago as the North American plate engulfed nearly all of the Farallon plate. Since then, the North American plate has ground against the Pacific plate at a boundary called a strike-slip fault.

Detailed explanation-5: -Tectonic Plate Boundaries The Pacific Plate (on the west) slides horizontally northwestward relative to the North American Plate (on the east), causing earthquakes along the San Andreas and associated faults. The San Andreas fault is a transform plate boundary, accomodating horizontal relative motions.