Garlock Fault

The Garlock Fault is a left-lateral strike-slip fault running approximately northeast-southwest along the north margins of the Mojave Desert of Southern California. It runs for much of its length along the southern base of the Tehachapi Mountains.

The Garlock Fault marks the northern boundary of the area known as the Mojave Block, as well as the southern ends of the Sierra Nevada and the valleys of the westernmost Basin and Range province. Stretching for 250 kilometers (160 mi), it is the second-longest fault in California and is one of the most prominent geological features in the southern part of the state.

The Garlock Fault runs from a junction with the San Andreas Fault in the Antelope Valley, eastward to a junction with the Death Valley Fault Zone in the eastern Mojave Desert. It is named after the historic mining town of Garlock, founded in 1894 by Eugene Garlock and now a ghost town.

The Garlock Fault is believed to have developed to accommodate the strain differential between the extensional tectonics of the Great Basin crust and the right lateral strike-slip faulting of the Mojave Desert crust.

Unlike most of the other faults in California, slip on the Garlock Fault is left-lateral; that is, the land on the other side of the fault moves to the left from the perspective of someone facing the fault. In the case of the Garlock Fault, this means that the terrain north of the fault is moving westward relative to the terrain south of the fault, which is moving relatively eastward.

The Garlock Fault moves at a rate of between 2 and 11 mm a year, with an average slip of around 7 millimeters. While most of the fault is locked, certain segments have been shown to move by aseismic creep.

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