The Hosgri Fault (also Hosgri Fault Zone, San Gregorio-Hosgri Fault Zone) is an offshore fault zone located near the Central Coast of California in San Luis Obispo County. The main fault stretches for about 87 miles (140 km), and is located nearest to the coastal communities of Cambria, San Simeon, Morro Bay, Baywood Park-Los Osos and Avila Beach.^[1] The fault system (including its branches) is some 260 mi (420 km) long, and is a right-lateral strand of the San Andreas Fault system.^[2]

The Hosgri Fault is a component of the San Andreas Fault system.^[3] Its movement is primarily reverse thrust, as well as exhibiting right lateral slip, and is thought to be capable of generating earthquakes of up to magnitude 7.5.^[1] The November 4, 1927 Lompoc earthquake (magnitude 7.1) is thought to have occurred (uncertainty) on this fault.^[4]

Seismologists monitor activity on the Hosgri fault constantly because of its physical proximity to the nuclear Diablo Canyon Power Plant. In fact, the fault lies only 2+1⁄2 miles offshore from the nuclear power plant.^[5] More recently in 2008, yet another even closer fault was discovered, the Shoreline Fault 1 mile from the NPP.

35°07′N 119°39′W