The longest and most active tectonic fault in the world is the San Andreas fault, located on the Carrizo Plain in California, USA.
In some places San Andreas is visible as a ravine, in others it is almost invisible. But especially clearly visible from the air or on the Carrizo Plain
1. The legendary San Andreas Fault was formed as a result of the collision of the Pacific and North American lithospheric plates. Being their border, the fault originates in Mexico, crosses the state from south to north, passing by Los Angeles through San Bernardino, and goes into the ocean right under San Francisco 
2. The depth of the fault reaches at least 16 km, and the length is 1,280 km (from east to south of California). All earthquakes occur along this boundary. 
3. 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 roads that cross the San Andreas Fault: displaced road markings and signs of regular road repairs are visible at the fault site.
4. In the San Gabriel Mountains north of Los Angeles, the asphalt of streets sometimes swells as forces accumulating along a fault line put pressure on the mountain range. As a result, on the western side, rocks compress and crumble, annually forming up to 7 tons of fragments, which are getting closer and closer to Los Angeles. 
5. 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 in the area of the epicenter the “left” part of California shifted relative to the “right” by almost 7 meters
6. The shift began 10 kilometers under the ocean floor in the San Francisco area, after which, within 4 minutes, the shear impulse spread over 430 kilometers of the San Andreas fault - from the village of Mendocino to the town of San Juan Bautista. The earthquake measured 7.8 on the Richter scale. The whole city was flooded. 
7. By the time the fires broke out, more than 75% of the city had already been destroyed, 400 city blocks lay in ruins, including the center. 
8. Two years after the devastating earthquake in 1908, geological research began, which continues to this day. Research has shown that over the past 1,500 years, major earthquakes have occurred along the San Andreas Fault approximately every 150 years. 
9.
The legendary San Andreas Fault was formed as a result of the collision of the Pacific and North American lithospheric plates. Being their border, the fault originates in Mexico, crosses the state from south to north, passing by Los Angeles through San Bernardino, and goes into the ocean right under San Francisco
The fault reaches a depth of at least 16 km and a length of 1,280 km (from east to south of California). All earthquakes occur along this boundary.
"St. Andreas Fault. Will San Francisco disappear into the earth's crust?"
By Yuri Panchul, Sunnyvale, California
The Russian magazine “New Times” published my popular science article about geology, plate tectonics and experiments in artificially causing earthquakes.
Http://newtimes.ru/magazine/2008/issue063/doc-47647.html
In April 1906, an earthquake struck San Francisco, killing more than 3,000 people and leaving 300,000 homeless. 83 years later, another thing happened, although not so terrible in terms of consequences. Catastrophists predict: sooner or later there will be a big earthquake that will level San Francisco to the ground, and the city will disappear into huge gaps 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 have 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 a Soviet nuclear missile aimed at a certain point (“water tower”) in California, which would cause the state’s crust to split into two pieces. After this, the western part would be flooded Pacific Ocean, which would cause the deaths of most of the 30 million Californians, including residents of Los Angeles and San Francisco. Of course, this story was not born in the USSR Ministry of Defense, but was a distorted account of the 1978 Hollywood film “Superman”.
1300 km of fear
But is there a grain of reality in this story? The 1,300-kilometer-long San Andreas fault actually runs along the California coast, separating the Pacific and North American tectonic plates. The 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 was 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 “went” along the fault over millions of years 314 kilometers north and became Pinnacles National Monument.
Where are the continents heading?
What forces move thousands of kilometers of 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 were motionless, and sections of the earth’s crust moved only down and up, according to the theory of geosynclines accepted in the mid-19th century.
But since the 16th century, cartographers have noticed that the coasts of Africa and South America may be superimposed on each other, like two pieces of a broken plate, after which some researchers have periodically put forward the idea that the continents are moving. The German scientist Alfred Wegener gave the most arguments. In 1915, Wegener showed that the coasts of different continents not only coincide in contour, but also contain the same types of rocks, 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 considered a bunch of random coincidences, since geophysicists believed it was impossible that a continent (a mass of rock) could move on another mass of rock (the solid floor of the oceans) without being destroyed by friction. The situation changed only after World War II, when the US military, using sonar, mapped the oceans and discovered in the middle of them long chains of seamounts, clearly of volcanic origin. Researcher Harry Hess showed that the floor of the Atlantic Ocean is moving in two directions from a mountain range running in the middle of the Atlantic. The spreading ocean floor carries continents like a subway escalator carries passengers.
And who moves them...
As a result of the research of Hess and other scientists 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 plate 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 continents.
When plates collide, depending on the nature of the collision, mountains are formed (for example, the Himalayas), chains of islands (for example, Japanese islands), depressions and volcanoes. When the oceanic and continental plates collide, the oceanic plate moves down. This is due to the fact that the ocean crust has a different chemical composition and greater density. Gerry Hess called the process a “conveyor belt”: new crust is born from solidified lava in the middle of the ocean, moves slowly for millions of years, after which it sinks back into the depths and melts.
Why do plates on the San Andreas Fault move sideways and not towards each other? The fact is that for 40 million years, a complex “dance” of three tectonic plates (Pacific, Farallon and North American) took place in the region, the boundaries between which passed at an angle to each other. The Farallon plate was “pushed” under the North American plate, after which the Pacific plate began to slide sideways along the former boundary of the Farallon and North American plates.
Tectonic plates are like froths driven by the 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 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 existence. We live on a huge nuclear reactor - planet Earth!
Earth shaking
Well, okay, continents are moving, but how does this affect our lives, besides the need to periodically repair several small roads crossing the San Andreas Fault? The point is that the movement is not continuous. Each shift begins with an accumulation 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 microearthquakes that are not felt by humans. But sometimes the tension 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 in the area of the epicenter the “left” part of California shifted relative to the “right” by almost 7 meters.
The shift began 10 kilometers under the ocean floor in the San Francisco area, after which, within 4 minutes, the shear pulse spread across 430 kilometers of the San Andreas Fault - from the village of Mendocino to the town of San Juan Bautista.
By the time the fires broke out, more than 75% of the city had already been destroyed, with 400 city blocks in ruins, including the center.
Two years after the devastating earthquake in 1908, geological research began, which continues to this day. Research has shown that over the past 1,500 years, major earthquakes have occurred along the San Andreas Fault approximately every 150 years.
The main villain's plan
Thus, it is impossible to flood coastal California with a targeted 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 plate is less realistic than sinking an aircraft carrier with a kick. But is it possible to cause serious destruction with an artificial earthquake? Oddly enough, this idea was tested not only in Hollywood films. In 1966, geologists from the US Geological Survey (USGS) noticed an unexpected sequence of earthquakes in the area of the Rocky Flats military arsenal in Colorado. The timing of the earthquakes coincided exactly with the moments when the military got rid of liquid waste by pumping it under pressure deep into the ground. Geologists conducted an experiment by pumping water into an abandoned oil deposit near Rangeley, Colorado. For the first time in history, people artificially caused an earthquake.
After this, the USGS briefly discussed the idea of preventing large earthquakes along the San Andreas by releasing fault stress using a large number of microquakes. However, the USGS decided not to experiment, since it is clear that they would not have enough money to pay in case of an error for the complete destruction of Los Angeles or San Francisco.
It could be worse
Despite the earthquakes, California is one of the nicest places to live on Earth. Most of the state's residents live in one or two-story houses and know the safety precautions. Therefore, the significant earthquake in San Francisco in 1989 did not cause much destruction. After all, there are problems in other places on the planet - hurricanes, tsunamis or unfavorable political conditions. And the San Andreas Fault is not the most dangerous geological feature in the United States. For example, there is the Yellowstone supervolcano, which about two million years ago covered the entire western half with ash. modern territory USA. A huge number of animals died even thousands of kilometers from the eruption - due to dust that entered the lungs and contaminated 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. Man-made earthquake – http://www.usgs.gov/newsroom/article.asp?ID=343
Used sources.
According to the script of the famous disaster film, 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.
Still from the film “San Andreas Fault” (2015)
California is one of the most seismically active regions in the United States. It is here that the notorious transform fault is located between two huge lithospheric plates: the North American and Pacific. The plates are in constant motion, and the result of increasing stress is earthquakes. The fault begins 160 kilometers north of San Francisco and runs southeast toward the Gulf of California, passing directly under San Francisco and 40 kilometers north of Los Angeles. A number of other faults pass through the area of this fault, forming a dense network of potentially dangerous geological formations.
Powerful earthquakes have already occurred on the Pacific coast of the United States, caused by movements of the earth's crust associated with the San Andreas fault. The last major earthquake in California occurred in 1989, and the epicenter of the events was the vicinity of Mount Loma Prieta. As a result of the 7.0-magnitude earthquake, the city of Santa Cruz suffered the most, killing 62 people and injuring more than 3.5 thousand.
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 formed. During the numerous destructions, about 3,000 residents of San Francisco and nearby communities were killed, and more than 80% of all buildings in the city were damaged as a result of the disaster.
Aftermath of the 1906 San Francisco earthquake The situation is complicated by the fact that the US Pacific Coast is the most densely populated region of the country. The state of California (as of 2015) had a population of 39 million. The San Andreas Fault runs 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. There are many others in potential danger settlements, which are located in southern California.
Los Angeles
American geologists believe that in the near future a powerful earthquake with an intensity of at least 7 points should occur in California. Such concerns are related to 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 regularly recorded 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 casualties and cause significant damage to the region's infrastructure.
Manifestation of the San Andreas Fault in the terrain Introduction
In recent years, there have been regular publications that a global eruption or earthquake is about to occur in the United States, which will destroy most of the country and have a negative impact on other countries. And everything speaks about this - the number of earthquakes has become more frequent, the temperature in the geysers has risen, the layers of the earth have begun to subsidence, cracks have appeared in the soil, animals are leaving the dangerous area.... I don’t know, I don’t know how correct this is. One gets the impression that most of the authors of such messages publish them for the sake of sensation or in the thirst for anticipation of the end of the world on a separate hated part of the Earth. Decide for yourself how much you can trust them. But today a new message has appeared about expectations of a catastrophe in the San Andreas Fault area.
At the end there is a list of posts and links on Conte about future earthquakes on the West Coast of the United States and the Yellowstone volcano.
In the coming days, America faces a tragedy worse than Fukushima
America faces a 9.3 magnitude earthquake if ten aftershocks occur on the mainland within ten days. Such power of earthquakes can cause a devastating tsunami on the west coast of America, experts are sure.
In California, along the San Andreas Fault, ten tremors of moderate strength have occurred in recent days - an average of one per day. The last one was three miles from Yucca Valley yesterday, the US Geological Survey said. These were relatively weak tremors with a magnitude of 3.6, scientists recorded movement at a depth of 1.2 km.
San Andreas tectonic fault
Similar small tremors (about two hundred in total) were felt from Santa Barbara all the way to the border with Mexico. All underground shaking occurred in one area, so scientists expect a devastating continuation - a powerful shock with a magnitude of more than nine points.
According to Express, emergency services are already preparing to deal with the most powerful earthquake in the Cascadia subduction zone (subduction is an area of the Earth where tectonic plates plunge under one another). From this area the disaster is expected to move north along west coast America.
Most powerful for Lately An earthquake occurred in Borrego Springs, San Diego, last Friday. Its magnitude was 5.2, and rescue efforts lasted four days.
More frequent tremors with a power of three on the Richter scale have raised concerns about the near future of the American continent. According to scientists, Express writes, the California fault line and the Cascadia subduction zone have long threatened America with a major shake-up.
Scientists from the US Geological Survey released the results of their analysis, based on computer modeling. Scientists' findings indicate that the San Andreas fault in California is capable of producing tremors with a power of 8.3. The results of the research made Americans very nervous: in 1906, San Francisco was almost wiped off the face of the earth by an earthquake with a magnitude of only 7.9.
The scientists' computer model allowed them to identify the areas of Cascadia that cause the greatest concern. The main risk area extends 60 miles along the Pacific Coast from Northern California to Vancouver Island.
Portland, Seattle and Vancouver are in the zone of a powerful tsunami that could destroy major infrastructure and take the lives of millions of people. According to Express, the US Geological Survey has every reason to expect an earthquake of up to 9.3 magnitude, which will entail a crushing wave.
To explain the scale of the expected disaster, scientists cite the example of the earthquake that struck Japan in 2011. Thousands of people died then a large number of buildings and cities were destroyed and flooded, breakdowns occurred at 11 nuclear power units (the largest accident was the shutdown of the Fukushima nuclear power plant).
San Andreas Fault: the calm before the storm
June 10, 2016
San Andreas
Seismologists are good observers. With the advent of a new generation of geophysical instruments and data processing methods, they are able to not only intercept all the vibrations produced by earthquakes, but also hear every tectonic groan or creak of our planet. In this regard, areas at the boundaries of tectonic plates, which remain “silent” for a long time and do not emit even a dim seismic whisper, are of particular concern.
Along the San Andreas Fault, in central and southern California, there are several such places whose stubborn silence remains a constant mystery to experts. In a report published this week in the scientific journal Science, seismologists Yunle Jiang and Nadia Lapusta of the California Institute of Technology proposed a new model to explain this uncharacteristic silence on certain sections of the fault.
To understand their arguments, it is worth first describing the nature of the San Andreas and the mechanical behavior of the earth's crust along its entire length. The rift runs through California, connecting two underwater mid-ocean ridges where volcanic activity forms a new ocean floor. One ridge is located off Cape Mendocino, the other is in the Gulf of California off the Mexican mainland.
Throughout its entire length, the San Andreas cuts through the continental crust, consisting of rocks of different ages, structures and geological features. As a result of this heterogeneity, different fault segments respond differently to tectonic movements of the Pacific and North American plates. In some areas, the San Andreas moves in parallel with the movement of plates, and in others it gets stuck for several decades, after which it releases the accumulated pressure in moderate to strong tremors.
On the one hand, such variability can be called favorable for people living along the San Andreas, since in the event of a catastrophic earthquake, crustal displacement is unlikely to occur along the entire 1,300-kilometer length of the fault. But on the other hand, this unevenness significantly complicates the forecasts of seismologists.
Typically, earthquakes along the San Andreas occur at shallow depths (about 10–12 km), where the earth's crust consists primarily of brittle rocks - quartz and feldspar. On fault sections that generate regular tremors, this fragile area is the source of continuous microseisms - tiny earthquakes with a magnitude of less than 2.0 on the Richter scale. But in those segments where earthquakes occur quite rarely, microseisms are completely absent.
It is important to note that these quiet segments correspond to areas that produced very powerful and energetic earthquakes in the historical and prehistoric past. These include, for example, the magnitude 7.8 Fort Tejon earthquake in 1857, which is comparable to the infamous 1906 San Francisco earthquake.
According to Jiang and Lapusta, the calm in certain areas of the San Andreas is due to the fact that the earth’s crust in these places is torn into much greater depth than previously thought. Accordingly, earthquakes here occur 3–5 km below the seismogenic zone, that is, not in brittle feldspar, but in more pliable and warmer layers of the earth, and therefore do not produce microseismic “rumble,” but quiet, viscous waves.
If Jiang and Lapusta's model is correct, it rings alarm bells for seismologists because it means that fault sections that generate constant microseisms are less dangerous than quiet segments that accumulate pressure over centuries. It is still unclear why these particular areas produce rare but very powerful earthquakes, but the study authors believe that they have an unusually uniform frictional force, so that if they shift, they rupture with terrifying integrity.
San Andreas on the map
For those who want to dive deeper into the topic, see a selection of publications on Conte about the West Coast:
The United States will host unprecedented exercises simulating a magnitude 9 earthquake and mega tsunami in the Cascadia subduction zone on May 30
In the US state of California, numerous cases of deformation of the earth's surface were noted on April 24
Some of the world's largest megacities are located right in the area of the most dangerous faults in the earth's crust. Californians living along 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, parking lots, Street lights every few steps. However, a closer look reveals that the line of the same lamps is not entirely straight, and the street seems to be twisted, as if it were taken by the ends and pulled into different directions. The reason for these oddities is that Taft, like many of California's major urban centers, is built along the San Andreas Fault, a crack in the Earth's crust that runs 1,050 km across the United States.
The strip, which stretches from the coast north of San Francisco to the Gulf of California and extends approximately 16 km inland, represents the line between two of the 12 tectonic plates on which the Earth's oceans and continents 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 as their location changes. If they creep on top of each other, huge mountain ranges such as the Alps and Himalayas rise into the sky. However, the circumstances that gave rise to the San Andreas Fault are completely different.
Here, the edges of the North American (on which much of this continent rests) and Pacific (which supports most of the Californian coast) tectonic plates are like ill-fitting gear teeth that do not fit one another, but do not fit neatly into the grooves intended for them. The plates rub against one another, and the friction energy generated along their boundaries has no outlet. Where such energy accumulates in the fault determines where the next earthquake will occur and how strong it will be.
In the so-called “floating zones,” where plate movement occurs relatively freely, the accumulated energy is released in thousands of small tremors, causing virtually no damage and recorded only by the most sensitive seismographs. Other sections of the fault - they are called “lock zones” - seem completely motionless, where the plates are pressed against one another so tightly that no movement occurs for hundreds of years. The tension gradually increases 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 zones, is nevertheless significant. The city of Parkfield, located between San Francisco and Los Angeles, lies in this intermediate zone. Earthquakes with a magnitude of up to b 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 to this region.
Since 200 AD e. There have been 12 major earthquakes in California, but it was the 1906 disaster that brought the San Andreas Fault to the attention of the whole world. This earthquake, with its epicenter in San Francisco, caused destruction over a colossal area stretching from north to south for 640 km. Along the fault line, the soil shifted 6 m in a matter of minutes - fences and trees were toppled, roads and communication systems were destroyed, the water supply stopped, and fires that followed the earthquake raged throughout the city.
As geological science has developed, more advanced measuring instruments have appeared that can constantly monitor the movements and pressure of water masses under the earth's surface. For a number of years before major earthquake seismic activity is increasing slightly, 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 amount of ground vibration. Thanks to these measures, the 1989 San Francisco earthquake destroyed mostly older structures without causing damage to modern skyscrapers.
Then 63 people died - most due to the collapse of a huge section of the double-decker Bay Bridge. According to scientists, California is facing a serious disaster in the next 50 years. An earthquake with a magnitude of 7 on the Richter scale is expected to occur in southern California, in the Los Angeles area. It could cause billions of dollars in damage and claim 17,000-20,000 lives, with smoke and fires potentially killing an additional 11.5 million people. And because frictional energy along a fault line tends to accumulate, each year that gets us closer to an earthquake increases its likely severity.
