A strike-slip fault is a zone where the land moves in a side-to-side motion instead of a vertical one. Most of the major faults in the United States are slip-strike faults.
Faults are weak areas in rock that allow the land to fracture to relieve stress. When the rock breaks or the land moves along the fault line, the vibration causes an earthquake. In strike-slip faults, the land ruptures in an almost vertical position. The San Andreas Fault is a special type of strike-slip joint that occurs between two crustal plates. This transform fault travels begins in the Pacific Ocean and travels almost two-thirds of the length of California to where the North American Plate and the Pacific Plate join the Juan de Fuca Plate.