occurred on the afternoon of January 16 with an estimated magnitude of about 6.7, with a possible offshore location, and high felt intensities in Southern California communities. Santa Barbara and San Bernardino reported an MM intensity of V and Los Angeles reported V and VI. Two significant events occurred in the San Bernardino area on December 15–16, 1858, with the latter having an estimated magnitude of about 6. The last recorded major aftershock occurred on April 16, 1860, with an estimated magnitude of about 6.3, with an epicenter close to the Parkfield section of the San Andreas Fault. Future threat Scientists and public service officials have speculated on the threat of another very large earthquake occurring in southern California and what type and scale of damage might result. The portion of the fault that ruptured in 1857 has settled into a period of dormancy and this has given rise to suggestions that future slip along that zone may be characterized by a very large 1857-type event followed by another period of inactivity. The communities of Frazier Park, Palmdale, and Wrightwood are all located very close to the San Andreas fault, though much of the Los Angeles area could be affected even at a greater distance from the rupture area if a similar event were to reoccur there. Swaminathan Krishnan, assistant professor of civil engineering and geophysics at the California Institute of Technology, said that if a similar rupture from Parkfield to Wrightwood were to happen again, it would severely affect the Los Angeles area, with the San Fernando Valley being particularly hard hit. The Los Angeles Aqueduct and California Aqueduct, two of the principal water transfer infrastructure systems supplying Greater Los Angeles, both cross the San Andreas fault within the main damage zone of the Fort Tejon earthquake, in the Tehachapi and Sierra Pelona Mountains. See also List of earthquakes in California List of earthquakes in the United States List of historical earthquakes References Bibliography Further reading External links Reports of the Great California Earthquake of 1857 – Scripps Institution of Oceanography The San Andreas Fault System, California – USGS Professional Paper #1515 – United States Geological Survey 1857 1857 earthquakes 1857 in California History of Southern California San Emigdio Mountains Sierra Pelona Ridge Tehachapi Mountains History of Kern County, California History of Ventura County, California History of Los Angeles County, California History of Santa Barbara County, California Mountain Communities