San Andreas Fault: a rare case when a film script turns into reality. San Andreas Fault in California San Andreas California

American scientists were seriously frightened by a series of 10 earthquakes that occurred last week in Monterey County, California, in the west of the country. The event has raised fears that the region could be seriously affected by a major disaster in the near future, the Daily Star reported.

According to the publication, the strongest shock was a magnitude 4.6 13 miles northeast of Gonzales in the area of ​​the San Andreas Fault. In this notorious zone, which stretches along the entire California, according to seismologists, a serious earthquake with a magnitude of at least 7.0 has long been brewing.

Within a radius of several kilometers from the underground disturbance of magnitude 4.6, another 134 tremors occurred during the week. Of these, 17 had a magnitude greater than 2.5, and six had a magnitude greater than 3.0.

Ole Kaven, a seismologist with the USGS, said he expects more aftershocks in the coming weeks.

We suspect aftershocks in the 2.0 to 3.0 range for at least several weeks

- Caven

There have been no reports of injuries or significant damage from the earthquakes so far.

Seismological experts are confident that such a number of tremors has sharply increased the chances of a colossal earthquake in the region in the short term. Forecasts of a powerful cataclysm awaiting the United States are already overdue, they say, by about 50 years or more. Tension along the San Andreas Fault has been building for 150 years, and this is leading to a major disaster.

Seismologist Lucy Jones of the US Geological Survey said a major earthquake was being considered as the most likely cause of the disaster in California.

When we have a big earthquake in the San Andreas area, it will be felt in Las Vegas, Arizona, and the San Francisco Bay Area

- Jones

The damage and death toll could be catastrophic, she said. So, we can talk about the destruction of about 300 thousand houses, the death of thousands of people and damage of hundreds of billions of dollars.

The San Andreas is a 1,300 kilometer long fault between the North American and Pacific plates. It runs along the coast of the state of California, mostly on land. The fault is associated with earthquakes reaching magnitude 9.0 and causing surface displacements of up to seven meters. The most serious disasters occurred in this area in 1906 and 1989. On February 26, 2016, the Global Forecast System recorded high and large-scale concentrations of carbon monoxide in the west coast of the United States and Canada. The gas release occurred near major geological faults across a wide area from British Columbia through Washington, Oregon and to California. Geologists and geochemists see this as a sign of an upcoming powerful earthquake.

Previously, American experts predicted in densely populated tropical regions of the world in 2018. The reason for this will be a change in the speed of rotation of the Earth - the planet will move a little slower than usual.

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

The process goes:

• September 19 new strong earthquake in Mexico, magnitude 7.1.
• September 20 In California, flashes were observed in the sky, immediately after this phenomenon, an earthquake of 3.6 magnitude occurred in the Beverly Hills area and these mysterious lights, which are also called “earthquake lights,” became harbingers of the earthquake that had occurred.

Video of flashes over California

https://youtu.be/mOlP2XD8EXI

All this speaks of powerful tectonic processes occurring deep in the Earth’s crust. Tectonic plates have begun to move and this can provoke earthquakes with a magnitude of 9 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 California coast just 15 minutes after the earthquake. The number of casualties among the population and the scale of destruction will be enormous.

San Andreas Fault

The tremors off the coast of Mexico had a magnitude of 8 to 8.4. This is a very alarming sign for the United States, because the fault on which they occurred is closely connected with the Cascadia zone. This is where the Juan de Fuca Plate subducts under the North American Plate.

The length of this zone is 900 kilometers along the coast. As seismologists say, in California, in the San Andreas fault zone, one should be wary of an earthquake of even greater magnitude, since the seismic tremors of the Mexican earthquake are just harbingers of disaster.

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

The video shows seismic sensors, if they turn blue, it means the plate they are located on is moving down. If they are red, then vice versa up. Experts pay special attention to the San Andreas fault, where absolutely all seismic sensors are painted 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 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 US coastal cities will soon go under water Hurricane Maria weakens to Category 1, but danger of hitting the US remains

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 to a 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.

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 twist, as if it were taken by the ends and pulled in different directions.

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

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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 “locking 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 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 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 communications systems were destroyed, water supplies 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 a major earthquake, seismic activity increases 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.

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.

In the San Gabriel Mountains north of Los Angeles, the asphalt of streets sometimes bulges 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.

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

The shift began 10 kilometers under the ocean floor in the San Francisco area, after which, within 4 minutes, the shear impulse spread along 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.

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.

Plate tectonics is a major process that largely shapes the appearance of the Earth. The word “tectonics” comes from the Greek “tekton” - “builder” or “carpenter”; in tectonics, plates are called pieces of the lithosphere. 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 across the surface of the earth, but lithospheric plates. Moving slowly, they carry continents and the ocean floor with them. The plates collide with each other, squeezing out the earth's surface in the form of mountain ranges and mountain systems, or are pushed inwards, creating ultra-deep depressions in the ocean. Their mighty activity is interrupted only by brief catastrophic events - earthquakes and volcanic eruptions. Almost all geological activity is concentrated along plate boundaries.

San Andreas Fault The thick line running down from the center of the picture is a perspective view of California's famous San Andreas Fault. The image created using data collected by SRTM (Radar Topographic Imaging) will be used by geologists to study the dynamics of faults and the shapes of the Earth's surface resulting from active tectonic processes. This segment of the fault is located west of Palmdale, California, about 100 km northwest of Los Angeles. The fault represents an active tectonic boundary between the North American Plate on the right and the Pacific Plate 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: the San Gabriel Mountains on the left and the Tehachapi Mountains on the upper right. Another fault, the Garlock, lies at the foot of the Tehachapi Range. 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 California's Central Valley. Antelope Valley can be seen along the base of the hills on the right side of the image.

The San Andreas Fault runs along the line of contact between two tectonic plates - the North American and Pacific. The plates move relative to each other by about 5 cm per year. This creates severe stresses in the crust and regularly causes large earthquakes centered on the fault line. Well, small tremors happen here all the time. Until now, despite the most careful observations, it has not been possible to identify signs of an upcoming large earthquake in the data on weak tremors.

The San Andreas Fault, which cuts across the west coast of North America, is a transform fault, that is, one where two plates slide along each other. Near transform faults, earthquake foci are shallow, usually less than 30 km below the Earth's surface. The 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.

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.

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.

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. Many other communities located in southern California are also in potential danger.

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.