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Information AboutSan Andreas Fault |
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San Andreas Fault is a Geological Fault that spans a length of roughly 800 miles (1287 kilometres) through California , United States . The fault, a right-lateral strike-slip fault, marks a Transform Boundary between the Pacific Plate and the North American Plate . Segments The San Andreas Fault can be divided into three segments. The southern segment (known as the Mojave segment) begins near the Salton Sea and runs northward before it begins a slow bend to the west when it meets the San Bernardino Mountains . 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 . These mountains are a result of movement along the San Andreas Fault and are commonly called the Transverse Range . This segment of the fault is the most commonly analyzed of any earthquake fault in the world by geologists. 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. After crossing through Frazier Park , the fault begins to bend north. 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 section of the fault has a recurrence interval of roughly 140 - 160 years. Northwest of Frazier Park, the fault runs through the Carrizo Plain , a long treeless plain within which much of the fault is plainly visible. The Elkhorn Scarp defines the fault trace along much of its length within the plain. map of the fault in California]] The central segment of the San Andreas fault runs in a northwestern direction from Parkfield to Hollister . 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 . This results in the fault being able to move without the need of earthquakes. 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 to Cape Mendocino , where there is an unstable Triple Junction where three tectonic plates come together to form a geologically complex and highly unstable zone. To the north lies the Cascadia Subduction Zone , where the Juan De Fuca Plate and the last bit of its lower section sometimes called the Gorda plate, are being subducted under the margin of the North American plate. And west, along the continental shelf, lies the Mendocino fault zone, the strike-slip boundary between the main Juan de Fuca plate and the Pacific plate. Scientific research The small town of Parkfield, California lies along the San Andreas Fault. Seismologists discovered that this section of the fault consistently produces magnitude 6.0 earthquakes about every 22 years. Following earthquakes in 1857 , 1881 , 1901 , 1922 , 1934 and 1966 , scientists predicted an earthquake to hit Parkfield in 1993 . This quake eventually struck in 2004 (see Parkfield Earthquake ). 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. 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 kilometers into the Earth's crust and into the San Andreas Fault. An array of sensors will be installed to capture and record earthquakes that happen near this area. {Link without Title} Other research monitoring slip rates along the fault has shown that Los Angeles and San Francisco (which rest on opposite sides of the San Andreas Fault) are moving towards one another at a rate of 1/5 inch (0.6 cm) a year. Notable earthquakes The San Andreas Fault has had three notable earthquakes in historic times:
On 6.0 earthquake Struck At Parkfield, California on the San Andreas Fault. This earthquake was originally expected to occur in 1993 based on the latest Earthquake Prediction theories known at the time. Eleven more years elapsed before this prediction was finally fulfilled. Despite the extra time between events (38 years compared to an average recurrence interval of 22 years), the magnitude of the earthquake was no larger than originally expected. Trivia
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