US scientists have announced a premonition of a catastrophe near the San Andreas Fault. san andreas fault in california geological fault san andreas california

Introduction

In recent years, there have been regular publications that the United States is about to experience a global eruption, an earthquake that will destroy most of the country and have a negative impact on other countries. And everything speaks of this - the number of earthquakes has become more frequent, the temperature in geysers has risen, earth layers have begun to subside, 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 a sensation or in a thirst for anticipation of the end of the world on a separate hated part of the Earth. How much you can trust them is up to you. But today a new message appeared about the expectation of a catastrophe in the San Andreas fault area.

At the end is a list of posts and links to Conte about future earthquakes on the US West Coast and the Yellowstone volcano.

In the coming days, America faces a tragedy worse than Fukushima

America is threatened with an earthquake of magnitude 9.3 if ten tremors occur on the mainland within ten days. Such power of tremors can cause a devastating tsunami on the west coast of America, experts are sure.

In California, along the San Andreas Fault last days there were ten aftershocks of medium strength - an average of one per day. The latest was yesterday three miles from the Yucca Valley, the USGS said. These were relatively weak shocks with a magnitude of 3.6 points, scientists recorded movement at a depth of 1.2 km.

San Andreas tectonic fault

Similar small shocks (about two hundred of them were counted in total) were felt from Santa Barbara all the way to the border with Mexico. All underground shaking occurred in the same area, so scientists expect a crushing continuation - a powerful shock with a magnitude of more than nine points.

According to Express, emergency services are already preparing to fight the most powerful earthquake in the subduction zone of Cascadia (subduction is a region of the Earth where tectonic plates sink one under another). From this zone, the disaster is expected to move north along the American west coast.

The most powerful earthquake in recent memory hit Borrego Springs, San Diego last Friday. Its magnitude was 5.2 points, rescue work lasted four days.

The increasing frequency of tremors with a power of three points on the Richter scale has raised fears about the near future of the American continent. According to scientists, the 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 simulations. The findings of scientists indicate that the San Andreas fault in California is capable of producing 8.3 magnitude tremors. 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 has allowed them to identify the areas of Cascadia that cause the greatest concern. The main risk zone 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 can destroy large objects infrastructure and take the lives of millions of people. According to the Express, the US Geological Survey has every reason to expect an earthquake of magnitude up to 9.3, which will entail a crushing wave.

To explain the scale of the expected catastrophe, scientists cite the example of the earthquake that hit Japan in 2011. Then thousands of people died, a large number of buildings and cities were destroyed and flooded, breakdowns occurred at 11 power units of the nuclear power plant (the largest accident was the shutdown of the Fukushima nuclear power plant).

The 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 manage not only to intercept all the vibrations produced by earthquakes, but also to hear every tectonic groan or creak of our planet. In this regard, areas on the borders are of particular concern. tectonic plates, which remain “mute” for a long time and do not emit even a dim seismic whisper.

Along the San Andreas Fault, in central and southern California, there are several such places whose stubborn silence remains a constant mystery to specialists. In a report published this week in scientific journal Science, seismologists Yunl Jiang and Nadia Lapusta from California Institute of Technology proposed a new model to explain this uncharacteristic silence in certain parts of the fault.

To understand their arguments, it is worth first describing the nature of San Andreas and the mechanical behavior of the earth's crust throughout its length. The fault runs through California, connecting two underwater mid-ocean ridges, in which volcanic activity forms a new ocean floor. One ridge is located at Cape Mendocino, the other is in the Gulf of California off the mainland of Mexico.

Throughout its length, San Andreas cuts through the continental crust, consisting of rocks of different ages, structures and geological features. As a result of this heterogeneity, different segments of the fault react differently to tectonic shifts in the Pacific and North American plates. In some areas, San Andreas moves in parallel with the movement of the plates, while in others it gets stuck for several decades, after which it releases the accumulated pressure with moderate or 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, the earth's crust is unlikely to move along the entire 1300-kilometer length of the fault. But on the other hand, this unevenness significantly complicates the forecasts of seismologists.

As a rule, earthquakes along the San Andreas occur at shallow depths (about 10–12 km), where Earth's crust consists mainly of brittle rocks - quartz and feldspar. At fault sites that generate regular tremors, this fragile region is the source of continuous microseisms - tiny earthquakes of magnitude 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, earthquake Fort Tejon of magnitude 7.8 in 1857, comparable to the infamous San Francisco earthquake of 1906.

According to Jiang and Lapust, the lull in certain areas of San Andreas is due to the fact that the earth's crust in these places is torn to a much greater depth than previously thought. Accordingly, earthquakes here occur 3-5 km below the seismogenic zone, that is, not in fragile feldspar, but in more pliable and warmer layers of the earth, therefore they produce not a microseismic “roar”, but quiet, viscous waves.

If Jiang and Lapusta's model is correct, then it is a wake-up call for seismologists, as it means that fault areas 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 authors of the study believe that they have an unusually uniform frictional force, therefore, in the event of a shift, they are torn apart with terrifying integrity.

San Andreas on the map

For those who want to dive deeper into the topic, see a selection of posts on Conte about the West Coast:

The US will host an unprecedented exercise simulating a 9-magnitude 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

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: 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.

Powerful earthquakes have already occurred on the Pacific coast of the United States, 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 800,000 people. Many others are in potential danger. settlements which are located in southern California.

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 A country

USA USA

Language Year The release of the film "The San Andreas Fault" (original title - San Andreas) K:Movies 2015

Plot

Raymond Gaines is a Los Angeles Fire Department Bell 412 helicopter pilot. He is going through a divorce from his wife Emma. One of the reasons for the divorce is the tragic death of their daughter Malory while rafting, for which Ray blames himself. His second daughter Blake, planning to go to college, travels from Los Angeles to San Francisco on the private jet of her mother's boyfriend, Daniel Riddick.

Meanwhile, earthquake prediction seismologist Lawrence Hayes and his assistant Kim Park are close to a breakthrough in their research. Just at that moment, a strong tremor is recorded on the Hoover Dam, and the structure is destroyed. As a result of the collapse of the dam, Kim dies, and Hayes, who miraculously escaped, transmits a warning that a dangerous tectonic movement has begun in the San Andreas Fault. Then a powerful earthquake destroys Los Angeles. Ray, having flown in by helicopter, manages to save Emma from the roof of a collapsing building. He receives a call from Blake that she is stuck in a collapsed underground parking lot inside a car in San Francisco. Then the connection is interrupted. Daniel leaves the girl to her fate, but her brothers Ben and Ollie Taylor save her.

Ray and Emma travel to San Francisco. On the way, the helicopter breaks down, and they, having made an emergency landing in the parking lot, breaking through the window of a shopping center in the Bakersfield area, continue their journey, taking the car from the marauders. The path is blocked by a colossal rift in the ground, and they get to the city by finding the plane. The meeting point that Ray's daughter suggested is unavailable, and he assumes that Blake will be waiting for him in one of the skyscrapers. Dr. Hayes predicts that the earthquake will affect the entire state, and the next aftershocks will destroy San Francisco. One of Hayes' students hacks into the network of a television company, and the doctor, with the help of a journalist, manages to broadcast an evacuation warning. An earthquake of magnitude 9.6 almost completely destroys the city. The tsunami demolishes the Golden Gate Bridge and completes the death of the city. Ray and Emma are on a speedboat driving around town, finding Blake and the Taylor brothers inside one of the buildings. Diving inside, Ray gets to his daughter and brings her to the surface. The rescued heroes leave the city on a boat and get to a temporary camp for survivors. Ray's last words as he watches the scene of epic destruction: "We'll rebuild everything."

Cast

Actor	Role
Dwayne Johnson	Ray Gaines Ray Gaines
Carla Gugino	Emma Gaines Emma Gaines
Alexandra Daddario	Blake Gaines Blake Gaines
Paul Giamatti	Lawrence Hayes seismologist Lawrence Hayes
Hugo Johnston-Bart	Ben Taylor Ben Taylor
Art Parkinson	Ollie Taylor Ollie Taylor
Archie Punjabi	Serena Johnson Serena Johnson
Todd Williams	Marcus Crowlings Marcus Crowlings
Colton Haynes	Joby Joby
Ioan Griffith	Daniel Riddick Daniel Riddick
Will Yun Lee	Kim Park Dr. Kim Park
Kylie Minogue	Susan Riddick Susan Riddick
Megan Griffin	Natalie Natalie
Brianne Hill	Larissa, waitress Larissa, waitress

Creation

Development

On December 1, 2011, it was announced that New Line Cinema was developing an earthquake disaster film. San Andreas: 3D written by Jeremy Passmore and André Fabrizio. Allan Lob worked on the script. Produced by the 100 millionth 3D film Beau Flynn. On June 5, 2012, the studio began considering Brad Peyton as the film's director. On July 18, 2012, New Line Cinema approached Carlton Cuse to rewrite the script. On July 18, 2013, the studio brought in Carrie and Chad Hayes for another rewrite of the script. On December 17, 2013, Variety reported that the disaster film would be filmed at Village Roadshow Studios in the Gold Coast, Australia. It is produced by New Line Cinema and Village Roadshow Pictures, in association with Flynn Picture Company.

casting

filming

Filming began in April 2014 in Queensland. Filming locations also included Ipswich, Brisbane, Los Angeles, Bakersfield and San Francisco.

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Notes

Links

An excerpt characterizing the San Andreas Fault (film)

- And you all listen to me, - Rostov turned to the peasants: - Now the march to the houses, and so that I don’t hear your voice.
“Well, we didn’t make any offense. We are just being stupid. They’ve only done nonsense… I told you it was disorder,” voices were heard reproaching each other.
“So I told you,” Alpatych said, coming into his own. - It's not good, guys!
“Our stupidity, Yakov Alpatych,” voices answered, and the crowd immediately began to disperse and scatter around the village.
The bound two peasants were taken to the manor's yard. Two drunk men followed them.
- Oh, I'll look at you! - said one of them, referring to Karp.
“Is it possible to speak to gentlemen like that?” What did you think?
“Fool,” another confirmed, “really, fool!”
Two hours later the carts were in the courtyard of Bogucharov's house. The peasants were eagerly carrying out and stacking the master's things on the carts, and Dron, at the request of Princess Mary, released from the locker where he was locked up, standing in the yard, disposed of the peasants.
“Don’t put it down so badly,” one of the peasants said, A tall man with a round smiling face, accepting the casket from the hands of the maid. She's worth the money too. Why are you throwing it like that or half a rope - and it will rub. I don't like that. And to be honest, according to the law. That's how it is under the matting, but cover it with a curtain, that's important. Love!
“Look for books, books,” said another peasant, who was carrying out the library cabinets of Prince Andrei. - You do not cling! And it’s heavy, guys, the books are healthy!
- Yes, they wrote, they didn’t walk! - a tall chubby man said with a significant wink, pointing to the thick lexicons lying on top.

Rostov, not wanting to impose his acquaintance on the princess, did not go to her, but remained in the village, waiting for her to leave. Having waited for Princess Mary's carriages to leave the house, Rostov mounted on horseback and accompanied her on horseback to the path occupied by our troops, twelve miles from Bogucharov. In Jankovo, at the inn, he took leave of her respectfully, for the first time allowing himself to kiss her hand.
“You’re not ashamed,” blushing, he answered Princess Marya to the expression of gratitude for her salvation (as she called his act), “every guard would have done the same. If we only had to fight with the peasants, we would not let the enemy go so far, ”he said, ashamed of something and trying to change the conversation. “I am only happy to have had the opportunity to meet you. Farewell, princess, I wish you happiness and consolation and wish to meet you under happier conditions. If you don't want to make me blush, please don't thank me.
But the princess, if she did not thank him more with words, thanked him with the whole expression of her face, beaming with gratitude and tenderness. She couldn't believe him, that she had nothing to thank him for. On the contrary, for her it was undoubtedly that if he were not there, then she probably would have to die from both the rebels and the French; that he, in order to save her, exposed himself to the most obvious and terrible dangers; and even more undoubted was the fact that he was a man with a lofty and noble soul, who knew how to understand her position and grief. His kind and honest eyes, with tears coming out of them, while she herself, crying, spoke to him about her loss, did not go out of her imagination.
When she said goodbye to him and was left alone, Princess Mary suddenly felt tears in her eyes, and then, not for the first time, she asked herself a strange question, does she love him?
On the way further to Moscow, despite the fact that the situation of the princess was not joyful, Dunyasha, who was traveling with her in a carriage, noticed more than once that the princess, leaning out of the window of the carriage, smiled joyfully and sadly at something.
“Well, what if I did love him? thought Princess Mary.
No matter how ashamed she was to admit to herself that she was the first to love a man who, perhaps, would never love her, she consoled herself with the thought that no one would ever know this and that it would not be her fault if for the rest of her life, no one talking about loving the one she loved for the first and last time.
Sometimes she remembered his views, his participation, his words, and it seemed to her that happiness was not impossible. And then Dunyasha noticed that she, smiling, was looking out the window of the carriage.
“And he should have come to Bogucharovo, and at that very moment! thought Princess Mary. - And it was necessary for his sister to refuse Prince Andrei! - And in all this, Princess Mary saw the will of providence.
The impression made on Rostov by Princess Marya was very pleasant. When he thought about her, he felt merry, and when his comrades, having learned about the adventure that had happened with him in Bogucharov, joked to him that he, having gone for hay, had picked up one of the richest brides in Russia, Rostov became angry. He was angry precisely because the idea of marrying a pleasant for him, meek Princess Marya with a huge fortune more than once came to his mind against his will. For himself, Nikolai could not wish for a better wife than Princess Mary: marrying her would make the Countess, his mother, happy, and improve his father’s affairs; and even—Nikolai felt it—would have made Princess Marya happy. But Sonya? And this word? And this made Rostov angry when they joked about Princess Bolkonskaya.

Having taken command of the armies, Kutuzov remembered Prince Andrei and sent him an order to arrive at the main apartment.
Prince Andrei arrived in Tsarevo Zaimishche on the same day and at the same time of the day when Kutuzov made the first review of the troops. Prince Andrei stopped in the village near the priest's house, at which the commander-in-chief's carriage was stationed, and sat down on a bench at the gate, waiting for the Serene Highness, as everyone now called Kutuzov. On the field outside the village, one could hear the sounds of regimental music, then the roar of a huge number of voices shouting “Hurrah! to the new commander-in-chief. Immediately at the gate, about ten paces from Prince Andrei, taking advantage of the absence of the prince and the fine weather, stood two batmen, a courier and a butler. Blackish, overgrown with mustaches and sideburns, a little hussar lieutenant colonel rode up to the gate and, looking at Prince Andrei, asked: is the brightest here and will he be soon?
Prince Andrei said that he did not belong to the headquarters of his Serene Highness and was also a visitor. The hussar lieutenant colonel turned to the well-dressed batman, and the batman of the commander-in-chief said to him with that special contempt with which the batmen of the commanders-in-chief speak to the officers:
- What, brightest? It must be now. You that?
The hussar lieutenant colonel grinned into his mustache at the orderly, got off the horse, gave it to the messenger and went up to Bolkonsky, bowing slightly to him. Bolkonsky stood aside on the bench. The hussar lieutenant-colonel sat down beside him.
Are you also waiting for the commander-in-chief? said the hussar lieutenant colonel. - Govog "yat, accessible to everyone, thank God. Otherwise, trouble with sausages! Nedag" om Yeg "molov in the Germans pg" settled down. Tepeg "maybe and g" Russian talk "it will be possible. Otherwise, Cheg" does not know what they were doing. Everyone retreated, everyone retreated. Did you do the hike? - he asked.
- I had the pleasure, - answered Prince Andrei, - not only to participate in the retreat, but also to lose in this retreat everything that he had dear, not to mention the estates and home ... father, who died of grief. I am from Smolensk.
- And? .. Are you Prince Bolkonsky? It’s a hell of a place to meet: Lieutenant Colonel Denisov, better known as Vaska, said Denisov, shaking Prince Andrei’s hand and peering into Bolkonsky’s face with especially kind attention. Yes, I heard, he said sympathetically and, after a pause, continued : - Here is the Scythian war. This is all hog "osho, but not for those who puff with their sides. And you are Prince Andg "she Bolkonsky?" He shook his head. "Very hell, prince, very hell to meet you," he added again with a sad smile, shaking his hand.
Prince Andrei knew Denisov from Natasha's stories about her first fiancé. This recollection both sweetly and painfully carried him now to those painful sensations that he had not thought about for a long time, but which nevertheless were in his soul. Recently, there have been so many other and such serious impressions as leaving Smolensk, his arrival in the Bald Mountains, recently known about the death of his father - so many sensations were experienced by him that these memories had not come to him for a long time and, when they did, had no effect on him. him with the same strength. And for Denisov, the series of memories that Bolkonsky’s name evoked was the distant, poetic past, when, after dinner and Natasha’s singing, without knowing how, he proposed to a fifteen-year-old girl. He smiled at the memories of that time and his love for Natasha, and immediately turned to what passionately and exclusively now occupied him. This was the campaign plan he had come up with while serving in the outposts during the retreat. He presented this plan to Barclay de Tolly and now intended to present it to Kutuzov. The plan was based on the fact that the French line of operations was too long and that instead of, or at the same time, acting from the front, blocking the way for the French, it was necessary to act on their messages. He began to explain his plan to Prince Andrei.
“They can't hold this whole line. This is impossible, I answer that pg "og" vu them; give me five hundred people, I g "azog" vu them, this is veg "but! One system is pag" tizanskaya.

Earlier, after the earthquake on September 8 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 will lead to very destructive 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

Seismologists are good observers. With the advent of a new generation of geophysical instruments and data processing methods, they manage not only to intercept all the vibrations produced by earthquakes, but also to hear every tectonic groan or creak of our planet. In this regard, of particular concern are areas at the boundaries of tectonic plates, which for a long time remain "silent" and do not radiate even a dim seismic whisper.

Along the San Andreas Fault, in central and southern California, there are several such places whose stubborn silence remains a constant mystery to specialists. In a paper published this week in the scientific journal Science, seismologists Yunl Jiang and Nadia Lapusta of the California Institute of Technology proposed a new model to explain this uncharacteristic silence along certain sections of the fault.

As a rule, earthquakes along the San Andreas occur at shallow depths (about 10-12 km), where the earth's crust consists mainly of brittle rocks - quartz and feldspar. At fault sites that generate regular tremors, this fragile region is the source of continuous microseisms - tiny earthquakes of magnitude 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 Fort Tejon earthquake of magnitude 7.8 in 1857, which is comparable to the infamous San Francisco earthquake in 1906.