The Great Fort Tejon Earthquake of January 9, 1857 was the second largest earthquake recorded in the continental United States.* It left an incredible surface rupture scar that is more than 220 miles in length along the San Andreas fault. Its Richter Scale magnitude was estimated to be 7.9 to 8.0. This would rank it as a "Great Quake" where, in heavily populated areas, tremendous destruction and loss of life occurs (or about 20 times the magnitude and 89 times the strength of the 1994 Northridge earthquake). Yet, despite the destructive power of this monster, only two people were reported to have lost their lives. A woman at Reed's Ranch, near Fort Tejon, was killed by the collapse of an adobe house. An elderly man had fallen dead in the Los Angeles area. Southern California in 1857 was sparsely populated, especially in the areas most strongly shaken. This fact and good fortune kept loss of life to a minimum. Nevertheless, the effects of the earthquake were quite dramatic, even frightening. Property as far away as Santa Cruz was destroyed.
Were the Fort Tejon shock to occur today, the damage would easily run into the billions of dollars. Loss of life would probably be substantial. Some present day communities that lie on or near the 1857 rupture area are Wrightwood, Palmdale, Frazier Park, and Taft. Today, the U.S. Geological Survey estimates a seven percent chance of a similar-sized or greater earthquake for the Los Angeles area within the next 30 years.
* The Cascadia earthquake of 1700 in the Pacific Northwest was believed to be larger (magnitude 8.7–9.2). Alaska has experienced 11 earthquakes recored at magnitude 8.0 or larger.