<P> The fault was first identified in Northern California by UC Berkeley geology professor Andrew Lawson in 1895 and named by him after the Laguna de San Andreas, a small lake which lies in a linear valley formed by the fault just south of San Francisco . Eleven years later, Lawson discovered that the San Andreas Fault stretched southward into southern California after reviewing the effects of the 1906 San Francisco earthquake . Large - scale (hundreds of miles) lateral movement along the fault was first proposed in a 1953 paper by geologists Mason Hill and Thomas Dibblee . This idea, which was considered radical at the time, has since been vindicated by modern plate tectonics . </P> <P> Seismologists discovered that the San Andreas Fault near Parkfield in central California consistently produces a magnitude 6.0 earthquake approximately once every 22 years . Following recorded seismic events in 1857, 1881, 1901, 1922, 1934, and 1966, scientists predicted that another earthquake should occur in Parkfield in 1993 . It eventually occurred in 2004 . Due to the frequency of predictable activity, Parkfield has become one of the most important areas in the world for large earthquake research . </P> <P> In 2004, work began just north of Parkfield on the San Andreas Fault Observatory at Depth (SAFOD). The goal of SAFOD is to drill a hole nearly 3 kilometres (1.9 mi) into the Earth's crust and into the San Andreas Fault . An array of sensors will be installed to record earthquakes that happen near this area . </P> <P> The San Andreas Fault System has been the subject of a flood of studies . In particular, scientific research performed during the last 23 years has given rise to about 3,400 publications . </P>

When did the san andreas fault last erupt