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 and other prehistoric earthquakes. 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 am, an earthquake with an estimated magnitude of 7.9 that began just north of Carrizo Plain (note that magnitude estimates vary in the literature; see (Southern California Earthquake Data Center, [2010]; Grant and Sieh, 1993). The earthquake ruptured along the San Andreas Fault from San Bernardino to near Parkfield; a distance of nearly 225 miles (360 km). [In California, the 1857 earthquake was only rivaled by the Great San Francisco Earthquake of 1906 that was also in the same range of magnitude.] The earthquake was one of the strongest earthquakes in the United States and was felt throughout the California and southern Nevada. The quake did little damage in that the region because it was fairly sparsely populated at the time. Today, an earthquake of similar magnitude would likely produce billions of dollars in damage to regional urban areas from Los Angeles and throughout the San Joaquin Valley region, and beyond.

The 1857 slip along the San Andreas Fault was about 30 feet (9.5 meters). This 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 measurable 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 (Siek and Wallace, 1987).

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Last modified: 1/12/2011