home Biology Amazing san andreas fault. San Andreas Fault: a rare case when the script of the film turns into reality San Andreas Fault what happens

Amazing san andreas fault. San Andreas Fault: a rare case when the script of the film turns into reality San Andreas Fault what happens

Some of the world's largest megacities are located just in the area of the most dangerous faults in the earth's crust. Californians living on the San Andreas fault line are constantly threatened by devastating earthquakes.

At first glance, the streets of Taft, in central California, are no different from the streets of any other city in North America. Houses and gardens along wide avenues, car parks, street lights every few steps. However, a closer look reveals that the line of the same lamps is not quite straight, and the street seems to be twisted, as if it was taken by the ends and pulled in different directions. The reason for these oddities is that Taft, like many Californian large urban centers, is built along the San Andreas Fault - cracks in the earth's crust, 1050 km of which run through the United States.

The strip, stretching from the coast north of San Francisco to the Gulf of California and extending into the depths of the earth for about 16 km, is a line connecting two of the 12 tectonic plates on which the oceans and continents of the Earth are located.

The average thickness of these plates is about 100 km, they are in constant motion, drifting on the surface of the liquid inner mantle and colliding with each other with monstrous force when their location changes. If they crawl one on top of the other, huge mountain ranges rise into the sky, such as the Alps and the Himalayas. However, the circumstances that gave rise to the San Andreas fault are completely different.

Here, the edges of the North American (on which most of this continent rests) and Pacific (supporting most of the California coast) tectonic plates are like ill-fitting gear teeth that do not fit one over the other, but do not fit neatly into the grooves intended for them. The plates rub against each other, and the friction energy formed along their boundaries does not find an outlet. It depends on which part of the fault such energy accumulates, where the next earthquake will occur and what strength will be.

In the so-called "floating zones", where the movement of the plates is relatively free, the accumulated energy is released in thousands of small shocks, which do almost no damage and are recorded only by the most sensitive seismographs. Other sections of the fault - they are called "castle zones" - seem to be completely immovable, where the plates are pressed against each other so tightly that there has been no movement for hundreds of years. The tension gradually builds up until finally both plates move, releasing all the accumulated energy in a powerful jerk. Then earthquakes occur with a magnitude of at least 7 on the Richter scale, similar to the devastating San Francisco earthquake of 1906.

Between the two described above lie intermediate zones, whose activity, although not as destructive as in the castle, is nevertheless significant. The city of Parkfield, located between San Francisco and Los Angeles, is in such an intermediate zone. Earthquakes with magnitude up to 6 on the Richter scale can be expected here every 20-30 years; the last one happened in Parkfield in 1966. The phenomenon of earthquake cyclicity is unique for this region.

From 200 AD e. 12 major earthquakes occurred in California, but it was the 1906 disaster that attracted the attention of the whole world to the San Andreas Fault. This earthquake, with its epicenter in San Francisco, caused destruction in a colossal area stretching from north to south for 640 km. Along the fault line, in a matter of minutes, the soil shifted 6 m - fences and trees were knocked down, roads and communication systems were destroyed, the water supply stopped, and the fires that followed the earthquake raged throughout the city.

As the science of geology has developed, more advanced measuring instruments have appeared that can constantly monitor the movements and pressure of water masses under the earth's surface. During a number of years before a major earthquake, seismic activity increases somewhat, so it is quite possible that they can be predicted many hours or even days in advance.

Architects and civil engineers take into account the possibility of earthquakes and design buildings and bridges that can withstand a certain force of the earth's surface vibrations. Thanks to these measures, the 1989 San Francisco earthquake destroyed most of the buildings of the old structure, without harming modern skyscrapers.

Then 63 people died - most due to the collapse of a huge section of the two-tier Bay Bridge. According to scientists, in the next 50 years, California is facing a serious disaster. It is assumed that an earthquake with a magnitude of 7 on the Richter scale will occur in southern California, in the Los Angeles area. It could cause billions of dollars in damage and cause 17,000 to 20,000 deaths, and another 11.5 million people could die from smoke and fires. And since the energy of friction along the fault line tends to accumulate, each year that brings us closer to an earthquake increases its likely strength.

According to the scenario of the famous disaster movie, a devastating earthquake occurs in the city of Los Angeles. But what makes this film different from many other Hollywood fantasies is that the San Andreas Fault actually exists in California. This fault has already caused several destructive earthquakes and, as scientists believe, more dangerous manifestations can be expected from it in the near future.

Shot from the film "The San Andreas Fault" (2015)

California is one of the most seismically active regions in the US. It is here that the infamous transform fault is located between two huge lithospheric plates: the North American and Pacific. The plates are in constant motion, and earthquakes are the result of the growing tension. The fault begins 160 kilometers north of San Francisco and runs southeast to the Gulf of California, passing directly under San Francisco and 40 kilometers north of Los Angeles. A number of other faults pass in the area of this fault, forming a dense network of potentially dangerous geological formations.

On the Pacific coast of the United States, powerful earthquakes have already occurred, which were caused by the movements of the earth's crust associated with the San Andreas Fault. The last major earthquake in California occurred in 1989, and the vicinity of Mount Loma Prieta became the epicenter of the events. As a result of the 7-point earthquake, the city of Santa Cruz was hit hardest of all, in which 62 people died and more than 3.5 thousand were injured.

Aftermath of the 1989 Loma Prieta earthquake

In 1906, an earthquake of magnitude 7.7 occurred, the epicenter of which was located 3 kilometers from San Francisco. As a result of horizontal displacements, cracks up to 8 meters wide were formed. During the numerous destructions, about 3,000 residents of San Francisco and nearby settlements were killed, and more than 80% of all buildings in the city were damaged as a result of the elements.

Aftermath of the 1906 San Francisco earthquake

The situation is complicated by the fact that the Pacific coast of the United States is the most densely populated region of the country. The state of California (as of 2015) was home to 39 million people. The San Andreas fault passes in close proximity to the cities of Los Angeles (with a population of 3.8 million people) and San Francisco, which is home to more than 800 thousand people. Many other settlements located in southern California are also in potential danger.

Los Angeles

American geologists believe that in the near future a strong earthquake with an intensity of at least 7 points should occur in California. Such fears are connected with the fact that the southern part of the San Andreas fault has not shown powerful activity for a long time, although small fluctuations in the earth's surface are recorded regularly in the region. During long intervals between strong earthquakes, a colossal amount of energy accumulates in the lithosphere, requiring discharge. The next earthquake, according to seismologists, will affect Los Angeles, which will entail human casualties and cause significant damage to the infrastructure of the region.

The manifestation of the San Andreas fault in the terrain

Earlier, after the September 8 earthquake in Mexico, the US seismological service published a message that the earthquake gave a powerful impulse that affected the tectonic plates of the San Andreas fault.

The process goes:

September 19 a new strong earthquake in Mexico, magnitude 7.1 points.
September 20 in California, flashes were observed in the sky, immediately after this phenomenon, an earthquake of 3.6 points occurred in the Beverly Hills region and these mysterious lights, which are also called "earthquake lights", became the harbingers of the earthquake that occurred.

Flash video over California

https://youtu.be/mOlP2XD8EXI

All this speaks of powerful tectonic processes going deep in the Earth's crust. The tectonic plates are in motion and this could trigger a magnitude 9 earthquake in California, located in the San Andreas fault zone, which would lead to very devastating and catastrophic consequences. If this happens, it will cause a giant tsunami wave that will cover the coast of California in just 15 minutes after the earthquake. The number of casualties among the population and the scale of destruction will be enormous.

San Andreas Fault

Tremors near the coast of Mexico had a force of 8 to 8.4 points. This is a very worrying sign for the US, because the fault on which they occurred is closely related to the Cascadia zone. This is where the Juan de Fuca plate is subducting under the North American plate.

The length of this zone is 900 kilometers along the coast. According to seismologists, in California, in the San Andreas fault zone, it is worth fearing an earthquake of even greater strength, since the seismic tremors of the Mexican earthquake are just harbingers of disaster.

There have already been landslides and ground displacements in the fault area more than once, for example, on November 20, 2015, due to ground displacement, a section of the Vasquez Canyon road was closed, located about 30 km from Los Angeles and 20 km from the San Andreas. This is what the road has become

The video shows seismic sensors, if they turn blue, then the plate on which they are located is moving down. If red - then vice versa up. Specialists pay special attention to the San Andreas fault, where absolutely all seismic sensors turned into different colors.

Watch the waves from the M8.1 earthquake in Mexico travel across the lower 48!What are you looking at? Short answer — What do you see here are seismic waves from the earthquake in Mexico moving seismic stations in the US (each dot is a station). Red means the station is moving up and blue means the station is moving down. The spinning lines show the direction and size of other motions.Long answer — The USArray Ground Motion Visualization (GMV) is a video-based IRIS DMC product that illustrates how seismic waves travel away from an earthquake location by depicting the normalized recorded wave amplitudes at each seismometer location using colored symbols (see maps below). The color of each symbol depicts the amplitude of the vertical ground motion, as detected by the station’s seismometer (for TA stations this represents velocity of ground movement) and normalized to its peak amplitude. The color changes as waves of differing amplitude travel past the seismometer. Blue indicates downward ground motion while red represents upward ground motion with the darker colors indicating larger amplitudes.For large events like this one a 3-component GMV is also produced that uses “tailed” symbols with the direction and length of their tail representing the direction and amplitude of the normalized horizontal ground motion at the corresponding location respectively.For more information visit http://ds.iris.edu/ds/products/usarraygmv/To see more data products from the IRIS DMC related to this earthquake please visit http http://ds.iris.edu/spud/gmv/14211093

134 earthquakes in California - the San Andreas fault began to move Coastal cities of the United States will soon go under water Hurricane Maria downgrades to Category 1, but threat of hitting US remains

The reason for these oddities is that Taft, like many Californian large urban centers, is built along the San Andreas Fault, a crack in the earth's crust, 1050 km of which runs through the United States.

Let's find out more about him...

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Lithospheric plates move very slowly, but not constantly. The movement of the plates occurs approximately at the rate of growth of human nails - 3-4 centimeters per year. This movement can be seen on the roads that cross the San Andreas Fault, with shifted road markings and signs of regular pavement repair visible at the fault.

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In the San Gabriel Mountains region north of Los Angeles, the asphalt of the streets sometimes swells - these are forces accumulating along the fault line, pressing on the mountain range. As a result, on the western side, the rocks are compressed and crumbled, annually forming up to 7 tons of fragments, which are getting closer and closer to Los Angeles.

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If the tension of the layers is not discharged for a long time, then the movement occurs suddenly, with a sharp jerk. This happened during the 1906 earthquake in San Francisco, when the “left” part of California moved relative to the “right” by almost 7 meters near the epicenter.

The shift began 10 kilometers under the ocean floor in the San Francisco area, after which, within 4 minutes, the shift impulse spread to 430 kilometers of the San Andreas Fault - from the village of Mendocino to the town of San Juan Bautista. The earthquake was 7.8 on the Richter scale. The whole city was flooded.

By the time the fires broke out, more than 75% of the city had already been destroyed, with 400 city blocks lying in ruins, including the center.

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Two years after the devastating earthquake in 1908, geological research began, which continues to this day. Studies have shown that over the past 1500 years, major earthquakes have occurred in the San Andreas fault region, approximately every 150 years.

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Plate tectonics is the main process that largely shapes the face of the Earth. The word "tectonics" comes from the Greek "tekton" - "builder" or "carpenter", but in tectonics, pieces of the lithosphere are called plates. According to this theory, the Earth's lithosphere is formed by giant plates that give our planet a mosaic structure. It is not continents that move on the surface of the earth, but lithospheric plates. Slowly moving, they drag the continents and the ocean floor with them. Plates collide with each other, squeezing out the earth's firmament in the form of mountain ranges and mountain systems, or pushing deep into, creating ultra-deep depressions in the ocean. Their mighty activity is interrupted only by short catastrophic events - earthquakes and volcanic eruptions. Almost all geological activity is concentrated along plate boundaries.

San Andreas Fault The heavy line running down from the center of the figure is a perspective view of California's famous San Andreas Fault. The image, created with data collected by SRTM (Radar Topographic Exposure), will be used by geologists to study the dynamics of faults and landforms resulting from active tectonic processes. This fault segment is located west of Palmdale, California, about 100 km northwest of Los Angeles. The fault is an active tectonic boundary between the North American platform - on the right and the Pacific - on the left. In relation to each other, the Pacific platform is away from the viewer, and the North American platform is towards the viewer. Two large mountain ranges are also visible: on the left, the San Gabriel Mountains, and on the upper right, the Tehachapi. Another fault - Garlock, lies at the foot of the Tehachapi ridge. The San Andreas and Garlock faults meet in the center of the image near the town of Gorman. In the distance, above the Tehachapi Mountains, lies the Central California Valley. Antelope Valley is visible along the foot of the hills on the right side of the image.

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The San Andreas Fault runs along the line of contact between two tectonic plates - the North American and Pacific. The plates are shifting relative to each other by about 5 cm per year. This results in strong stresses in the crust and regularly generates strong earthquakes centered on the fault line. Well, small tremors happen here all the time. So far, despite the most careful observations, it has not been possible to identify signs of an upcoming major earthquake in the dataset on weak shocks.

The San Andreas Fault, which cuts through the western coast of North America, is a transform fault, that is, one where two plates slide along each other. Near transform faults, earthquake sources are shallow, usually at a depth of less than 30 km below the Earth's surface. Two tectonic plates in the San Andreas system move relative to each other at a rate of 1 cm per year. The stresses caused by the movement of the plates are absorbed and accumulated, gradually reaching a critical point. Then, instantly, the rocks crack, the plates shift and an earthquake occurs.

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This is not a shot from the filming of another disaster movie, and not even computer graphics.

Here we examined in detail this earthquake in the USA -

http://www.indiansworld.org/Articles/travel_san_andreas.html#.VQVwMY6sXWQ

https://ru.wikipedia.org/wiki/%D0%A0%D0%B0%D0%B7%D0%BB%D0%BE%D0%BC

http://galspace.spb.ru/index15.html

The legendary San Andreas Fault was formed as a result of the collision of the Pacific and North American lithospheric plates. As their border, the fault originates in Mexico, crosses the state from south to north, passing Los Angeles through San Bernardino, and goes into the ocean right under San Francisco

The fault is at least 16 km deep and 1,280 km long (from east to south of California). All earthquakes occur along this boundary.

"St. Andreas Fault. Will San Francisco disappear into the earth's crust?"
Author Yuri Panchul, Sunnyvale, California

The Russian magazine "New Times" (The New Times) published my popular science article on geology, plate tectonics and experiments on artificial induction of earthquakes.

http://newtimes.ru/magazine/2008/issue063/doc-47647.html

In April 1906, an earthquake hit San Francisco, killing more than 3,000 people and leaving 300,000 homeless. After 83 years, another thing happened, although not so terrible in terms of consequences. Catastrophists predict: sooner or later there will be a big earthquake that will raze San Francisco to the ground, and the city will disappear into huge breaches in the earth's crust. And the reason for this is a crack in the ground, called the St. Andreas Fault. Can a terrible earthquake be caused artificially? Where are the continents rushing and what forces pushed Africa away from South America - The New Times was looking for answers to these questions

During the Cold War, there was a story that there was supposedly a Soviet nuclear missile aimed at a certain point (“water tower”) in California, hitting which would cause the earth’s crust of the state to split into two pieces. After that, the western chunk would be inundated by the Pacific Ocean, which would cause the death of most of the 30 million Californians, including residents of Los Angeles and San Francisco. Of course, this tale was not born in the USSR Ministry of Defense, but was a distorted presentation of the 1978 Hollywood movie Superman.

1300 km of fear

But is there a grain of reality in this bike? A 1,300-kilometer-long San Andreas fault indeed runs along the coast of California, separating the Pacific and North American tectonic plates. San Andreas (together with the adjacent Hayward, Calaveras and other faults) is a source of large earthquakes.

The most visible manifestation of the “work” of the fault is the ancient volcano Ninah, which formed 23 million years ago, after which it was neatly, like a cake, “cut” by the San Andreas fault into two halves, and the left half “left” along the fault for millions of years. 314 kilometers to the north and became the Pinnacles National Monument.

Where are the continents going?

What forces move thousand-kilometer pieces of the earth's surface? Until the 20th century, the answer to this question was unknown. More precisely, there was not even a question: geological science believed that the continents are motionless, and sections of the earth's crust move only up and down, according to the theory of geosynclines adopted in the middle of the 19th century.

But since the 16th century, cartographers have noticed that the coasts of Africa and South America can be superimposed on each other, like two pieces of a broken plate, after which some researchers periodically put forward the idea that the continents are moving. Most of the arguments were given by the German scientist Alfred Wegener. In 1915, Wegener showed that the coasts of different continents not only coincided in contour, but also contained the same types of stones, as well as fossils of similar animal species. Wegener suggested that 200 million years ago there was a single supercontinent Pangea, which subsequently split into parts that became modern Eurasia, America, Australia and Antarctica. For 50 years, Wegener's theory was thought to be a set of coincidences, as geophysicists thought it improbable that a continent (a mass of rock) could move across another mass of rock (the hard bottom of the oceans) without being eroded by friction. The situation changed only after World War II, when the US military, using sonar, built maps of the oceans and found in the middle of them long chains of seamounts, clearly of volcanic origin. Researcher Harry Hess showed that the bottom of the Atlantic Ocean is moving apart in two directions from the mountain range passing in the middle of the Atlantic. The expanding ocean floor carries the continents like an escalator in a subway carries passengers.

And who drives them...

As a result of the research of Hess and others in the 1960s, a revolution occurred in geology comparable to the Copernican revolution in astronomy. It turned out that the earth's crust consists of several large plates (African, North American, Pacific, Eurasian and others), as well as a large number of small plates that move at a speed of several centimeters per year, colliding with each other. Each slab is about 100 kilometers thick. Beneath the plates that form the "lithosphere" is a hot, viscous layer about 200–400 kilometers thick called the asthenosphere. Tectonic plates “float” on it, carrying the continents.

When plates collide, depending on the nature of the collision, mountains are formed (for example, the Himalayas), chains of islands (for example, the Japanese islands), depressions and volcanoes. When the oceanic and continental plates collide, the oceanic plate goes down. This is due to the fact that the oceanic crust has a different chemical composition and greater density. Gerry Hess called the ongoing process a “conveyor belt”: a new crust is born from hardened lava in the middle of the ocean, slowly moves for millions of years, after which it sinks back into the bowels and melts.

Why are the plates on the San Andreas fault moving sideways and not towards each other? The fact is that for 40 million years in the region there was a complex "dance" of three tectonic plates (Pacific, Farallon (Farallon) and North American), the boundaries between which were at an angle to each other. The Farallon Plate was "pushed" under the North American, after which the Pacific began to slide sideways along the former border of the Farallon and North American plates.

Tectonic plates are like foams driven by convection currents of boiling soup. In the 19th century, scientists did not understand how this "soup" could continue to "boil" at all. According to the calculations of the famous physicist William Thomson (Lord Kelvin), according to the laws of thermodynamics, the Earth should have cooled down in just 20 million years. This contradicted geologists' estimates of the age of the Earth. Thomson did not take into account the heating of the Earth by the decay of radioactive elements, which were discovered only at the beginning of the 20th century. Because of this heating, the Earth continues to be hot after four and a half billion years of its existence. We live on a huge nuclear reactor - planet Earth!

earth shaking

Okay, the continents are moving, but how does this affect our lives, in addition to the need to periodically repair a few small roads that cross the San Andreas fault? The problem is that the movement is not continuous. Each shift begins with a buildup of stress, which is "discharged" by a jerk during a large or small earthquake. In the central part, the fault “creeps” due to thousands of micro-earthquakes that are not felt by humans. But sometimes the voltage is not discharged for a long time, after which the movement occurs in a jump.

This happened during the 1906 earthquake in San Francisco, when the “left” part of California moved relative to the “right” by almost 7 meters near the epicenter.

By the time the fires broke out, more than 75% of the city had already been destroyed, with 400 city blocks lying in ruins, including the center.

The villain's plan

Thus, it is impossible to flood coastal California with a point nuclear explosion on the San Andreas Fault. The plates in the fault area do not move towards each other, but to the sides (along the north-south line), so pushing the Pacific plate under the North American one is less realistic than flooding an aircraft carrier with a kick. But is it possible to cause serious damage with an artificial earthquake? Oddly enough, this idea was tested not only in Hollywood films. In 1966, geologists from the United States Geological Survey (USGS) noticed an unexpected sequence of earthquakes near the Rocky Flats military arsenal in Colorado. The timing of the earthquakes exactly coincided with the moments when the military disposed of liquid waste by pumping it under pressure deep underground. Geologists set up an experiment by pumping water into an abandoned oil field near the town of Rangely in Colorado. For the first time in history, humans artificially caused an earthquake.

After that, the USGS discussed for some time the idea of preventing large earthquakes along the San Andreas by relieving fault stress with a large number of micro-quakes. However, the USGS decided not to experiment, since it is clear that they would not have enough money to pay in case of a mistake for the complete destruction of Los Angeles or San Francisco.

It gets worse

Earthquakes notwithstanding, California is one of the nicest places to live on Earth. Most residents of the state live in one-two-story houses and know the precautions. Therefore, the significant San Francisco earthquake in 1989 did not cause much destruction. After all, there are problems elsewhere on the planet - hurricanes, tsunamis or an unfavorable political situation. And the San Andreas fault is not the most dangerous geological object in the United States. For example, there is the Yellowstone supervolcano, which about two million years ago covered the entire western half of the modern United States with ash. A huge number of animals died even thousands of kilometers from the eruption - due to dust that got into the lungs and polluted drinking water. Such eruptions change the climate of the entire planet for years, causing a "volcanic winter". But the topic of volcanoes and supervolcanoes deserves a separate article.

Information sources:

1 Michael Collier A Land in Motion - California's San Andreas Fault. Golden Gate National Parks Conservancy. University of California Press, 1999.

2. Allan A. Schoenherr. A Natural History of California. University of California Press, 1995

3. Sandra L. Keith. Pinnacles National Monument. Western National Parks Association. 2004.

4 Bill Bryson A Short History of Nearly Everything. Broadway Books, 2005.

5. Wikipedia - Plate Tectonics, San Andreas Fault, Supervulcano, etc.

6. Artificial earthquake - http://www.usgs.gov/newsroom/article.asp?ID=343

Used sources.