<Tr> <Th> Orogeny </Th> <Td> Gorda - California - Nevada </Td> </Tr> <P> The San Andreas Fault is a continental transform fault that extends roughly 1,200 kilometers (750 mi) through California . It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right - lateral strike - slip (horizontal). The fault divides into three segments, each with different characteristics and a different degree of earthquake risk . The slip rate along the fault ranges from 20 to 35 mm (0.79 to 1.38 in) / yr . </P> <P> The fault was identified in 1895 by Professor Andrew Lawson of UC Berkeley, who discovered the northern zone . It is often described as having been named after San Andreas Lake, a small body of water that was formed in a valley between the two plates . However, according to some of his reports from 1895 and 1908, Lawson actually named it after the surrounding San Andreas Valley . Following the 1906 San Francisco earthquake, Lawson concluded that the fault extended all the way into southern California . </P> <P> In 1953, geologist Thomas Dibblee concluded that hundreds of miles of lateral movement could occur along the fault . A project called the San Andreas Fault Observatory at Depth (SAFOD) near Parkfield, Monterey County, is drilling into the fault to improve prediction and recording of future earthquakes . </P>

When was the san andreas fault line discovered