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3D View of San Andreas Fault – Earthtopomaps 3D overlay imagery

Earth’s crust is a collection of fractured plates that shift across the planet’s surface over millions of years. Two of the major plates meet at the coast of California:. The Pacific Plate:. Under the ocean, is drifting slowly northwest:. Grinding along the margin of the North American Plate, to the east. Where they meet, the intense pressure of the collision creates an 800-mile-long fracture zone called the San Andreas Fault.

3D View of San Andreas Fault – Earthtopomaps 3D overlay imagery

Much of the length of the fault is lined by a distinct trough. This false-color NASA radar image shows a section of the fault west of San Francisco Bay;. The Crystal Springs Reservoir fills the trough that marks the underlying fault. The black line curving along the east side of the fault is I-280:. And California highway 92 runs from the top right across to the center left of the image:. Heading towards Half Moon Bay to the west. San Mateo and Burlingame are parts of the large urbanized area in various tones of pink and green:. And Foster City is the area of curved streets extending out into the San Francisco Bay at the top right.

The image was captured in November 2008 as part of a campaign to repeatedly collect detailed:. Three-dimensional images of the San Andreas Fault along the same flight path.

The goal is to map which parts of the fault are creeping past each other with little “stickiness,”:. And which parts appear to be locked together places where pent-up stress may be released suddenly in a major earthquake:. By repeatedly collecting images over an identical flight track, scientists can spot places where the topography is visibly deformed.

Ground deformation sometimes just a fraction of inch can indicate that far below the surface, the plates are stuck together.

To read more about NASA’s mission to map the San Andreas and related faults with radar imagery:. Please read Scientists Search for a Pulse in Skies Above Earthquake Country.

Gooble Earth Web: 3D View of San Andreas Fault

NASA image courtesy Jet Propulsion Laboratory. Caption by Rebecca Lindsey, based on the Planetary Photojournal’s image description.

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. (In this region around the San Francisco Bay Area several significant “sister faults” run more-or-less parallel:. And each of these can create significantly destructive earthquakes.):. After that, it runs underwater along the coast until it nears Cape Mendocino:. Where it begins to bend to the west, terminating at the Mendocino Triple Junction.

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Early years

Eleven years later, Lawson discovered that the San Andreas Fault stretched southward into southern California after reviewing the effects of the 1906 San Francisco earthquake. This idea, which was considered radical at the time:. Has since been vindicated by modern plate tectonics.

Current research

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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. It eventually occurred in 2004. Due to the frequency of predictable activity, Parkfield has become one of the most important areas in the world for large earthquake research.

A 2023 study found a link between the water level in Lake Cahuilla (now the Salton Sea) and seismic activity along the southern San Andreas Fault.

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3D View of San Andreas Fault – Earthtopomaps 3D overlay imagery

The study suggests that major earthquakes along this section of the fault coincided with high water levels in the lake. The hydrological load caused by high water levels can more than double the stress on the southern San Andreas Fault, which is likely sufficient for triggering earthquakes. This may explain the abnormally long period of time since the last major earthquake in the region since the lake has dried up.

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The San Andreas Fault System has been the subject of a flood of studies. In particular, scientific research performed during the last 23 years has given rise to about 3,400 publications.

3D View of San Andreas Fault – Earthtopomaps 3D overlay imagery

Cascadia connection

A 2008 paper, studying past earthquakes along the Pacific coastal zone, found a correlation in time between seismic events on the northern San Andreas Fault and the southern part of the Cascadia subduction zone (which stretches from Vancouver Island to northern California). Scientists believe quakes on the Cascadia subduction zone may have triggered most of the major quakes on the northern San Andreas within the past 3,000 years. The evidence also shows the rupture direction going from north to south in each of these time-correlated events.

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 motion between the Pacific and North American Plates was different from the relative motion between the Farallon and North.

3D View of San Andreas Fault – Earthtopomaps 3D overlay imagery

See also:

Earthtopomaps – Cape Verde Archipelago the island chain – 3D

The summary:

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 motion between the Pacific and North American Plates was different from the relative motion between the Farallon and North.

Wikipedia wiki San Andreas Fault

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Revised September 22, 2023