The San Andreas Fault is the boundary between the North American and Pacific Plate. It is anomolous that the westward movement of the North American Plate has not yet resulted in either plate undergoing suduction on their boundary. Instead, they are sliding sideways as the Pacific Plate is moving northwards at a rate of one to two inches per year.
The illustration on the right shows the various plates involved with the Pacific Plate's movement. Note that each of the other plates is subducting on the eastern edge, while it is subducting in the north at the Aleutian Trench. Not shown is the Jaun del Fuca Plate that is subducting under the Pacific Northwest. The triangular shaped plate south of Mexico is the Cocos Plate, which is the primary source of tectonic force driving the Mexican Disconnection.
Considered te primary source of tectonic activity in the west, the San Andreas Fault's steady movement has preoccupied geologists for the past century.
Although it is considered the primary source of California tectonic activity, there are many features of the land forms and fault lines that are clearly the result of east-west compression.
Look carefully at this map of the area and you will quickly recognize the patterns that support this idea and the specific patterns caused by the Mexican Disconnection.
The above illustration shows the southern California area with the faults in blue and the Interstate Highways in yellow. The increased number of faults and their direction is consistent with the Mexican Disconnection Theory.