What is the san andreas fault
The largest earthquakes in California since European settlers arrived struck in 18 on the San Andreas Fault. Map of the modern San Andreas Fault in relation to the greater plate-tectonic setting of western North America. "This material has less friction than on the northern and southern section of the fault, so the central section of the fault can creep." "They found some talc-like minerals," Wdowinski said. Rocks retrieved from the deep drilling project revealed that slippery clays may be responsible for some of the "creeping" behavior along the San Andreas Fault. Scientists predicted another earthquake should occur in 1993, but it didn't happen until 2004. It was the site of the first official earthquake prediction by the U.S. Parkfield, in central California, pops off a moderate earthquake of around magnitude 6 every couple decades, and is a center for earthquake research. In 2004, work began near the town of Parkfield on the San Andreas Fault Observatory at Depth(SAFOD) to drill nearly 2 miles (3.2 km) into the fault. The San Andreas Fault was the site of a massive effort to drill into Earth's crust and investigate a fault at depth. The stress on Earth's crust is relieved by building mountains (squeezing) and faulting, or breaking, the Earth's crust, such as the faults that slice up Los Angeles, Wdowinski said. This bend creates geologic squeezing and stretching between the two tectonic plates. Near the town of Gorman, the fault suddenly swings east for about 6 miles (10 km), the turns south again. South of the creeping section, the fault also has a visible "Big Bend" that helps push up some of southern California's spectacular mountain ranges. These stuck sections of the fault store energy like springs, slowly building up strain until - sproing! - they suddenly unzip and slide past one another in an earthquake. That's because the creeping section slowly, continuously moves, while the locked sections seem to get stuck. In historical times, this creeping section has not generated powerful earthquakes similar to those on the "locked" sections. The central, creeping section includes everything from Parkfield to Hollister. The southern segment stretches from Parkfield south through the Salton Sea. The northern segment runs from Hollister north through the Point Reyes National Seashore, then eventually moves offshore. Geologists divide the fault into northern and southern segments, separated in the middle by a curiously quiet portion that "creeps." The San Andreas Fault is about 800 miles long (1,287 kilometers), stretching from the Mendocino coast south to the San Bernardino Mountains and the Salton Sea. Geologists think the total amount of displacement along the fault is at least 350 miles (563 km) since it formed. For example, the volcanic rocks in Pinnacles National Park south of Monterey match volcanic rocks in Los Angeles County (called the Neenach volcanics). Researchers have measured identical rocks offset by 150 miles (241 kilometers) across either side of the fault. And stream channels with sharp jogs - the channels are offset across the fault line - can be visited in the central California's Carrizo Plain National Monument. "The dominant motion along the fault is primarily horizontal, but some areas also have vertical motion," noted Shimon Wdowinski, a geophysicist at the University of Miami's Rosentiel School of Marine & Atmospheric Sciences who has studied the San Andreas Fault. For example, sharp cliffs called scarps form when the two sides of the fault slide past each other during earthquakes. On the ground, one can find the San Andreas Fault by looking for landforms it created. Sometimes the boundary is a zone of several smaller faults, one or more of which may break during an earthquake. But viewed up close, there are actually many fractures and faults that mark the zone where the two plates slide past one each other. This narrow break between the two plates is called a fault. Viewed from space, the San Andreas Fault looks like a long, narrow valley that marks where the North America plate meets the Pacific plate.