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Geology of National Parks, 3D and Photographic Tours

San Andreas Fault at Wallace Creek

This view is looking south along the San Andreas Fault from the top of the fault scarp at Wallace Creek. The foot trail at the base of the hill basically follows the trace of the surface rupture associated with the Fort Tejon Earthquake. The trace of the fault can be seen as a line extending to the horizon. The Caliente Range on the west side of the Carrizo Plain can be seen in the distance.

The Great California Earthquake of 1857 (also known as the Fort Tejon earthquake) occurred on January 9, 1857 at 8:20 a. m. Its estimated magnitude was 7.9 (note that magnitude estimates vary in the literature (Southern California Earthquake Data Center, [2010]; Grant and Sieh, 1993). The San Andreas Fault ruptured from San Bernardino to near Parkfield, a distance of nearly 225 miles (360 km). It was one of the strongest earthquakes recorded in the United States, rivaled in California only by the Great San Francisco Earthquake of 1906. Although the Fort Tejon earthquake was felt throughout the California and southern Nevada, the quake did little damage because of the sparse population at the time. Today, a similar earthquake would likely cause billions of dollars in damage to the highly populated region of Los Angeles and surrounding areas.

On the Carrizo Plain, the rupture associated with the Fort Tejon earthquake displaced the western side of the San Andreas fault about 30 feet (9.5 meters) northward. This distance was determined from the offset of survey monuments established by a Township and Range survey conducted in 1855 and 1856 by James E. Freeman. Additional measurements of offset from the earthquake were derived from offset drainages, roads, and other features in the region (Grant and Sieh, 1993). Roads and fences constructed after the earthquake show that there has been no measurable fault creep or movement along the fault for the past hundred years (Sieh and Wallace, 1987).


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