<P> The Pacific Plate is a major section of the Earth's crust, gradually expanding by the eruption of magma along the East Pacific Rise to the southeast . It is also being subducted far to the northwest into the Aleutian Trench under the North American Plate well north of San Francisco . In California, the plate borders the North American Plate along a transform boundary, the San Andreas Fault . The westward component of the North American Plate's motion and the irregularity of the San Andreas Fault results in some compressive force along the San Andreas and its associated faults, thus helping lift the Coast Ranges . The Mount Diablo Thrust Fault and the Great Valley Blind Thrust faults are consequences of this compression . </P> <P> Movement along the Mount Diablo Thrust Fault includes crustal shortening of about 2.6 mm and uplift of about 1 mm per year . </P> <P> The Mount Diablo Thrust Fault is approximately 25 km long, and dips at an angle of 38 degrees to the northeast . The Mount Diablo Thrust Fault is capable of generating an earthquake of magnitude M = 6.7 . The predicted rupture surface begins 8 km below the surface, and there is thus no surface expression of the fault, and a low likelihood of surface rupture in the event of a large earthquake on the fault . No large historic earthquakes are known to have occurred on the Mount Diablo Thrust Fault . The recurrence interval for large earthquakes along the fault is predicted to be about 400 years . </P> <P> Compressive stresses are produced by offset and converging slip - strike motions between the Calaveras Fault and the Clayton - Marsh Creek - Greenville Fault which manifest in the Mount Diablo Thrust Fault . </P>

Quake here on thrust fault near san andreas