The goal of SAFOD is to drill a hole nearly 2.5 miles (4 kilometers) into the Earth's crust and into the San Andreas Fault. In 2004, work began just north of Parkfield on the San Andreas Fault Observatory at Depth (SAFOD). Because of this frequent activity and prediction, Parkfield has become one of the most popular spots in the world to try to capture and record large earthquakes. This quake eventually struck in 2004 (see Parkfield earthquake). Following earthquakes in 1857, 1881, 1901, 1922, 19, scientists predicted an earthquake to hit Parkfield in 1993. Seismologists discovered that this section of the fault consistently produces magnitude 6.0 earthquakes about every 22 years. The small town of Parkfield, California lies along the San Andreas Fault.
The northern segment of the fault runs from Hollister, through the San Francisco Peninsula where it briefly goes offshore, then follows the coast of California fairly closely before it makes a sharp turn west and goes offshore near Eureka, California. This results in the fault being able to move without the need of earthquakes. While the southern section of the fault and the parts through Parkfield experience earthquakes, the rest of the central section of the fault exhibits a phenomenon called aseismic creep. The central segment of the fault runs in a northwestern direction from Parkfield to Hollister. The Elkhorn Scarp defines the fault trace along much of its length within the plain.
Northwest of Frazier Park, the fault runs through the Carrizo Plain, a long treeless plain within which much of the fault is plainly visible. This section of the fault has a recurrence interval of roughly 140 - 160 years. This area is referred to as the "Big Bend" and is thought to be where the fault locks up in Southern California as the plates try to move past each other. This is due to a cutout of the fault in Palmdale, the second largest city directly sitting on the fault, where the Antelope Valley Freeway passes through it and the deep layers of "shifted" crust can clearly be seen.Īfter crossing through Frazier Park, the fault begins to bend northeast. This segment of the fault is the most commonly analyzed of any earthquake fault in the world by geologists. These mountains are a result of movement along the San Andreas Fault and are commonly called the Transverse Range. Here, it runs along the southern base of the San Bernardino Mountains, crosses through the Cajon Pass and continues to run northwest along the northern base of the San Gabriel Mountains. The southern segment begins in near the Salton Sea and runs northward before it begins a slow bend to the west when it meets the San Bernardino Mountains. The San Andreas Fault can be divided into 3 segments. Despite the extra time, the earthquake was no larger than originally expected. Eleven extra years elapsed before this prediction was finally fulfilled. This earthquake was originally expected to strike in 1993 based on then recently discovered theories of earthquake prediction. On Septemat 10:15 am, a magnitude 6.0 earthquake struck at Parkfield, California on the San Andreas Fault.