How many miles has the San Andreas Fault moved?
Geologists believe that the total accumulated displacement from earthquakes and creep is at least 350 miles along the San Andreas fault since it came into being about 15-20 million years ago.
Why is the San Andreas Fault a strike-slip fault?
The Northern Pacific plate is sliding laterally past the North American plate in a northerly direction, and hence the San Andreas is classified as a strike-slip fault.
How often do earthquakes occur on the San Andreas Fault?
Current research 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.
Is the San Andreas fault constantly moving?
The two plates grind against each other along the fault, producing seismic events, moving 0.79 to 1.38 inches per year in a process called continental drift. The San Andreas Fault is made up of three sections, each shifting independently past each other like two hands being rubbed together.
How often is the San Andreas fault active?
Moving at 5 to 7 centimeters a year, the San Andreas is one of the most active fault zones in the world.
What is the average rate of movement along the San Andreas fault?
Geologic rates The rate of plate movement along the San Andreas fault, 33 millimeters (1.3 inches) each year, is about how fast your fingernails grow. As a result, Los Angeles City Hall is now 2.7 meters (9 feet) closer to San Francisco than when it was built in 1924.
When was the last time the San Andreas fault moved?
San Andreas FaultStatusActiveEarthquakes1857, 1906 (Mw ≈7.8), 1957 ( Mw 5.7), 1989 ( Mw ≈6.9), 2004TypeTransform faultMovementDextral16 more rows
What year will the big one hit?
The chart tells us the average interval between large earthquakes is 138 years, plus or minus 30 years. Based on this average and standard deviation, the next large earthquake on the Hayward fault could be anywhere between 1977 and 2036, or even later, of course.
How likely is it that San Andreas fault will happen?
Because of the time needed to accumulate slip equal to a 20 ft offset, there is only a small chance (about 2 percent) that such an earthquake could occur in the next 30 years, according to the report of the Working Group on California Earthquake Probabilities.
What would happen if the San Andreas fault slipped?
Death and damage About 1,800 people could die in a hypothetical 7.8 earthquake on the San Andreas fault — that's according to a scenario published by the USGS called the ShakeOut. More than 900 people could die in fires, more than 600 in building damage or collapse, and more than 150 in transportation accidents.
What is the biggest fault line in the world?
San Andreas Fault -- the biggest fault on Earth | San andreas fault, Earthquake, Earthquake fault lines.
Is the San Andreas fault drifting at a rate of 2 inches per year?
Although it is difficult to imagine this great amount of shifting of the Earth's crust, the rate represented by these ancient offsets is consistent with the rate measured in historical time. Surveying shows a drift at the rate of as much as 2 inches per year. Movement of blocks along the San Andreas fault.
How overdue is a Big One on the San Andreas fault?
200 yearsParts of the San Andreas fault have not ruptured in over 200 years, meaning it's overdue for a high-magnitude earthquake commonly referred to as "The Big One."
What states will feel the San Andreas fault?
It slices California in two from Cape Mendocino to the Mexican border. San Diego, Los Angeles and Big Sur are on the Pacific Plate. San Francisco, Sacramento and the Sierra Nevada are on the North American Plate.
Will there be a tsunami after San Andreas fault?
Tsunami Science The San Andreas fault cannot create a big tsunami, as depicted in the movie.
What is the average rate of motion on faults?
The faults are most commonly found around the edge of plates which are continental-size blocks of rocks that comprise the outermost part of the earth. These plates are constantly moving (albeit very slowly) at rates up to four inches per year (10 cm/yr) although most rates of travel are considerably less.
How Fast Is San Andreas moving?
San Andreas Fault Zone – The Big Picture The relative motion between these two tectonic plates is 50 mm/yr (about 2 inches/yr), but that rate is distributed across all the faults that are part of the SAFZ.
What type of movement happens along the San Andreas Fault?
The San Andreas Fault—made infamous by the 1906 San Francisco earthquake—is a strike-slip fault. This means two fault blocks are moving past each other horizontally. Strike-slip faults tend to occur along the boundaries of plates that are sliding past each other.
What kind of movement does the San Andreas Fault have?
A San Andreas earthquake would be classified as occurring on a strike-slip fault. Strike-slip faults are found along boundaries of tectonic plates sliding past each other. A strike-slip fault is a vertical fracture in the earth's crust that creates horizontal motion, along the line of the fault.
How long has the San Andreas fault been around?
The main southern section of the San Andreas Fault proper has only existed for about 5 million years.
How long will the San Andreas fault slide past San Francisco?
Assuming the plate boundary does not change as hypothesized, projected motion indicates that the landmass west of the San Andreas Fault, including Los Angeles, will eventually slide past San Francisco, then continue northwestward toward the Aleutian Trench, over a period of perhaps twenty million years.
How many segments does the San Andreas fault have?
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. It was formed by a transform boundary.
What is the name of the mountain range that runs through the San Andreas fault?
These mountains are a result of movement along the San Andreas Fault and are commonly called the Transverse Range.
What plate is the San Andreas fault?
A continental transform fault through California between the Pacific Plate and the North American Plate. This article is about the continental fault in California. For other uses, see San Andreas (disambiguation). San Andreas Fault. The fault, right, and the Carrizo Plain, left.
What was the magnitude of the San Francisco earthquake in 1957?
1957 San Francisco earthquake: A magnitude 5.7 quake with an epicenter on the San Andreas fault in the ocean west of San Francisco and Daly City.
What is the effect of the North American plate movement?
The effect is expressed as the Coast Ranges. The northwest movement of the Pacific Plate is also creating significant compressional forces which are especially pronounced where the North American Plate has forced the San Andreas to jog westward. This has led to the formation of the Transverse Ranges in Southern California, and to a lesser but still significant extent, the Santa Cruz Mountains (the location of the Loma Prieta earthquake in 1989).
What is the San Andreas fault?
According to the theory of plate tectonics, the San Andreas Fault represents the transform ( strike-slip) boundary between two major plates of the Earth’s crust: the Northern Pacific to the south and west and the North American to the north and east. The Northern Pacific plate is sliding laterally past the North American plate in a northerly direction, and hence the San Andreas is classified as a strike-slip fault. The movement of the plates relative to each other has been about 1 cm (0.4 inch) per year over geologic time, though the annual rate of movement has been 4 to 6 cm (1.6 to 2.4 inches) per year since the early 20th century. Parts of the fault line moved as much as 6.4 metres (21 feet) during the 1906 earthquake.
Where does the Pacific Ocean fault go?
The fault trends northwestward for more than 800 miles (1,300 km) from the northern end of the Gulf of California through western California, U.S., passing seaward into the Pacific Ocean in the vicinity of San Francisco.
How long ago were the Klamath Mountains?
North America: 30 to 2.5 million years ago. …to North America along the San Andreas Fault system.
Which fault was responsible for the 1906 earthquake that all but destroyed San Francisco?
United States: The Western Cordillera. …ridges, and the greatest—the notorious San Andreas Fault —was responsible for the earthquake that all but destroyed San Francisco in 1906. Along the California–Oregon border, everything changes again.
Is BART a fault zone?
Some cities, towns, housing developments, and roads are actually built on it, and a tunnel of the San Francisco Bay Area Rapid Transit System (BART ) is bored right through the fault zone.
How to find the San Andreas fault?
On the ground, one can find the San Andreas Fault by looking for landforms it created . For example, sharp cliffs called scarps form when the two sides of the fault slide past each other during earthquakes. "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. 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.
When did the San Andreas fault occur?
The San Andreas Fault was born about 30 million years ago in California, when the Pacific Plate and the North America plate first met. Before then, another oceanic plate, the Farallon plate, was disappearing beneath North America at a subduction zone, another type of plate boundary. The new configuration meant the two plates slid past one another instead of crashing into each other, a boundary called a strike-slip fault.
What is the cause of the creeping of the San Andreas fault?
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. "They found some talc-like minerals," Wdowinski said. "This material has less friction than on the northern and southern section of the fault, so the central section of the fault can creep."
How many miles are there on the Neenach fault?
Researchers have measured identical rocks offset by 150 miles (241 kilometers) across either side of the fault. For example, the volcanic rocks in Pinnacles National Park south of Monterey match volcanic rocks in Los Angeles County (called the Neenach volcanics). Geologists think the total amount of displacement along the fault is at least 350 miles (563 km) since it formed.
What is the name of the valley that marks where the North America plate meets the Pacific plate?
Viewed from space, the San Andreas Fault looks like a long, narrow valley that marks where the North America plate meets the Pacific plate. This narrow break between the two plates is called a fault. But viewed up close, there are actually many fractures and faults that mark the zone where the two plates slide past one each other.
What is the bend in the California fault?
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. Near the town of Gorman, the fault suddenly swings east for about 6 miles (10 km), the turns south again. This bend creates geologic squeezing and stretching between the two tectonic plates. 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.
What is the biggest earthquake in California?
California's sleeping giant, the San Andreas Fault, marks the slippery yet sticky boundary between two of Earth's tectonic plates. It is responsible for the biggest earthquakes in California, up to at least magnitude 8.1.
How long is the San Andreas fault?
The entire San Andreas fault system is more than 800 miles long and extends to depths of at least 10 miles within the Earth.
When did the San Andreas fault occur?
The San Andreas Fault. The presence of the San Andreas fault was brought dramatically to world attention on April 18 , 1906 , when sudden displacement along the fault produced the great San Francisco earthquake and fire. This earthquake, however, was but one of many that have resulted from episodic displacement along the fault throughout its life ...
When Could the Next Large Earthquake Occur Along the San Andreas Fault?
Geologic studies show that over the past 1,400 to 1,500 years large earthquakes have occurred at about 150-year intervals on the southern San Andreas fault. As the last large earthquake on the southern San Andreas occurred in 1857 , that section of the fault is considered a likely location for an earthquake within the next few decades. The San Francisco Bay area has a slightly lower potential for a great earthquake, as less than 100 years have passed since the great 1906 earthquake; however, moderate-sized, potentially damaging earthquakes could occur in this area at any time.
What Can Be Done About the Faults and Earthquakes?
Even though people cannot stop earthquakes from happening, they can learn to live with the problems caused by earthquakes. Three major lines of defense against earthquake hazards are being developed. Buildings in earthquake-prone areas should be designed and constructed to resist earthquake shaking. Building codes that require attention to earthquake shaking have been improving in recent decades and constitute a first line of defense. In some cities, programs are underway to strengthen or tear down older buildings most likely to collapse during earthquakes. A second line of defense involves the selective use of land to minimize the effects of hazardous ground. High- occupancy or critical structures, for example, should not be placed astride the San Andreas fault or on landslide-prone areas. The third line of defense will be the accurate prediction of earthquakes. When such prediction becomes possible, it will permit timely evacuation of the most hazardous buildings. A major program aimed at learning how to predict earthquakes and to assess and minimize their hazards was initiated following the Earthquake Hazards Reduction Act of 1977 and is being carried out by the U.S. Geological Survey, other Federal Agencies, universities, and private groups.
How many feet was the road across the head of Tomales Bay?
During the 1906 earthquake in the San Francisco region, roads, fences, and rows of trees and bushes that crossed the fault were offset several yards, and the road across the head of Tomales Bay was offset almost 21 feet, the maximum offset recorded. In each case, the ground west of the fault moved relatively northward.
What is the displacement of a block on the opposite side of the San Andreas fault?
Geologists refer to this type fault displacement as right-lateral strike-slip.
Where are the plates that meet on the Earth's surface?
Two of these moving plates meet in western California; the boundary between them is the San Andreas fault.
Overview
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 th…
Fault zones
The northern segment of the fault runs from Hollister, through the Santa Cruz Mountains, epicenter of the 1989 Loma Prieta earthquake, then up the San Francisco Peninsula, where it was first identified by Professor Lawson in 1895, then offshore at Daly City near Mussel Rock. This is the approximate location of the epicenter of the 1906 San Francisco earthquake. The fault returns onshore at Bolinas …
Plate boundaries
The Pacific Plate, to the west of the fault, is moving in a northwest direction while the North American Plate to the east is moving toward the southwest, but relatively southeast under the influence of plate tectonics. The rate of slippage averages about 33 to 37 millimeters (1.3 to 1.5 in) a year across California.
The southwestward motion of the North American Plate towards the Pacific is creating compress…
Formation
The San Andreas began to form in the mid Cenozoic about 30 Mya (million years ago). At this time, a spreading center between the Pacific Plate and the Farallon Plate (which is now mostly subducted, with remnants including the Juan de Fuca Plate, Rivera Plate, Cocos Plate, and the Nazca Plate) was beginning to reach the subduction zone off the western coast of North America. As the relative mo…
Study
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 o…
Earthquakes
The San Andreas Fault has had some notable earthquakes in historic times:
• 1857 Fort Tejon earthquake: About 350 kilometers (220 mi) were ruptured in central and southern California. Though it is known as the Fort Tejon earthquake, the epicenter is thought to have been located far to the north, just south of Parkfield. Two deaths were reported. Its moment magnitude was 7.9.
See also
• California earthquake forecast
• Central Valley (California) – Flat valley that dominates central California
• Coast Range Geomorphic Province
• Garlock Fault – Fault running along the margins of the Mojave Desert of Southern California,United States
Further reading
• Collier, Michael (December 1, 1999). A Land in Motion. UC Press. ISBN 978-0-520-21897-0.
• Stoffer, Philip W. (2005). The San Andreas Fault In The San Francisco Bay Area, California: A Geology Fieldtrip Guidebook To Selected Stops On Public Lands. USGS. General Interest Publication 16.
Beginnings
Norcal vs. SoCal
- 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 divide the fault into northern and southern segments, separated in the middle by a curiously quiet portion that "creeps." [Photo Journal: The Gorgeous San Andreas Fault] The northern segment runs from H…
Earthquake Prediction
- The San Andreas Fault was the site of a massive effort to drill into Earth's crust and investigate a fault at depth. 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. Parkfield, in central California, pops off a moderate earthquake of around magnitude 6 every couple decades, and i…
Earthquake History
- The largest earthquakes in California since European settlers arrived struck in 1857 and 1906 on the San Andreas Fault. The Jan. 9, 1857, Fort Tejon earthquake in southern California, an estimated magnitude 7.9, offset stream channels by as much as 29 feet (9 m). The U.S Geological Survey estimates that a similar-size earthquake today, in the same ...