The San Andreas is a transform fault. Numerous smaller faults are associated with the San Andreas and, together with the main San Andreas fault, they are responsible for the numerous and powerful earthquakes in California. California is moving north and will reach Alaska in about 50 million years. Fault Types Faults are fractures in rocks, where rocks on either or both sides of the fault occasionally move and generate earthquakes. Faults may range from only a few meters to hundreds of kilometers long.
Most faults ultimately form because of forces generated by the movement of tectonic plates.
The rocks surrounding a fault are called the hanging wall and the foot wall. The hanging wall is located above the fault and the foot wall is located below. Reverse faults are common near subduction zones or continent-continent collisions, where rocks are being pushed on top of other rocks. A thrust fault is a special type of reverse fault. In a thrust fault, the angle between the fault plane and horizontal is less than 30 o .