home epics Fracture of the earth's crust san andreas. The San Andreas Fault: a rare case when the script of the film turns into reality

Fracture of the earth's crust san andreas. The San Andreas Fault: a rare case when the script of the film turns into reality

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, a crack in the earth's crust, 1050 km of which runs 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 one another 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 capable of constantly monitoring movements and pressure water masses below the earth's surface. During 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 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 faces 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.

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.

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.

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.

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.

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.

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. Until now, despite the most careful observations, to identify in the array of data on weak shocks signs of the coming major earthquake failed.

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.

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

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. This event raised fears that the region could be seriously affected by major disaster reported the Daily Star.

According to the publication, the strongest was a shock of magnitude 4.6 13 miles northeast of Gonzales in the San Andreas Fault. In this infamous zone that stretches across California, according to seismologists, a serious earthquake with a magnitude of at least 7.0 is long overdue.

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

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

We suspect that for at least a few weeks, aftershocks ranging from 2.0 to 3.0
- Caven

There have been no reports of injuries or significant damage from earthquakes yet.

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

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

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

According to her, the damage and the number of deaths can be simply catastrophic. So, we can talk about the destruction of about 300 thousand houses, the death of thousands of people and damage in the hundreds of billions of dollars.

San Andreas is a fault between the North American and Pacific plates 1300 kilometers long. It runs along the coast through the state of California, mostly on land. Earthquakes are associated with the fault, reaching a magnitude of 9.0 and causing surface displacements of up to seven meters. The most serious cataclysms occurred in this area in 1906 and 1989. On February 26, 2016, the Global Forecast System recorded a high and large-scale concentration of carbon monoxide in the West Coast region of the United States and Canada. The release of gas occurred near large geological faults in a vast area from British Columbia through the states of Washington, Oregon and to California. Geologists and geochemists see this as a sign of an upcoming powerful earthquake.

Earlier, 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 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

Road workers in the California city of Hayward repaired a shifted curb that was a clear example of the activity of the Hayward Fault. Seismologists have been watching this curb for over 45 years. /website/

The famous curb was at the intersection of Rose and Prospect streets. It gradually shifted relative to another curb, which aroused great interest among scientists. From 1974 to 1979, the curb, along with part of the road, moved about two centimeters. Over time, the adjacent curb slabs completely ceased to touch.

However, the local authorities decided to repair the road and installed a wheelchair ramp at the site of the shift. It turned out that the city administration simply did not know about the importance of this place. “If we knew about the shift, we probably would have looked at the curb differently, and even tried to help scientists document it,” said Kelly McAdoo, assistant mayor.

"It is sad. It was a real disappointment. Indeed, it was unusual to have such evidence of a break right here. Now scientists are left with only photographs that document the pavement slipping over the years,” Oakland science journalist Andrew Alden wrote on his blog.

This shift most clearly demonstrated the movement of the Pacific and North American tectonic plates, but there was other evidence of underground activity. In addition to the displacement of curbs, seismologists observed cracks in the asphalt, divergence of columns in the colonnade of a sports stadium, and other signs. Scientists collected more accurate data using high-precision sensors installed at the boundaries of the fault.

Studying the displacement of the curb was very important for scientists, since the movement of the Pacific and North American tectonic plates in the near future could cause a strong earthquake. In addition, the displacement of these plates caused a much more dangerous fault - the San Andreas Fault. While the Hayward Fault occupies part of the overall movement between the plates, the San Andreas Fault is a major boundary transformation between the Pacific and North American plates.

San Andreas Fault

This fault extends 1,300 kilometers along the California coast, mostly overland. The fault goes deep into about 16 kilometers. The thickness of the lithospheric plates is about 100 kilometers. They drift on liquid lava, crawling one on top of the other, causing earthquakes and other cataclysms.

The edges of two slabs in the San Andreas fault look like ill-fitting gear teeth. They rub against each other, and the friction energy generated along their boundaries finds no way out. In places where the movement of plates is relatively free, the accumulated energy is released in thousands of small shocks. They cause almost no damage and are recorded only by sensitive devices.

In other places, the plates are pressed quite strongly, and when they move, they release powerful energy at once. Then earthquakes occur with a magnitude of at least 7 on the Richter scale. Such an earthquake could occur within the next 50 years, seismologists say. It can cause billions of dollars of damage and up to 20,000 deaths.

double break

San Andreas is considered the most likely site of the next seismic event in the next few decades. However, the catastrophe could be more devastating if San Andreas activity hits the San Jacinto Fault, which runs through San Bernardino, Riverside, San Diego and Imperial County in Southern California.

Julianna S. Lozos, an assistant professor of geological sciences at the University of California at Riverside, determined that a similar event happened about 200 years ago. It caused a powerful jolt that was felt over a wide area from Los Angeles to San Diego. The 7.5-magnitude San Juan Capistrano earthquake on December 8, 1812, was the result of two faults rupturing at the same time, Lozos said.

It was previously thought that the tremor was caused by the San Andreas Fault. However, computer simulations showed that the earthquake began further south - in the San Jacinto region, and then involved San Andreas in the disaster. The activity of two faults at the same time can be very dangerous for California. The infrastructure of the state is built taking into account the tremors caused by one fault. The consequences of a simultaneous break can be unpredictable.

Cascadia Fault

The Cascadia Fault, which stretches 900 kilometers from Vancouver Island to Northern California, also poses a serious danger to the United States. Cascadia is located at the junction of the oceanic plate and the North American plate. A plate from the ocean squeezes the continental one, as a result of which it shrinks by 30–40 mm annually.

According to seismologists, sooner or later the pressure between the plates will accumulate to the limit, after which there will be a strong push, leading to a mega-earthquake with a magnitude of 8.7 to 9.2. The shock will cause a giant wave, some of which will even reach Japan. The wave can rise to a height of up to 30 meters, seismologists say. According to the American Emergency Management Agency (FEMA), Cascadia could cause the death of 13,000 people.

Seismologists consider Cascadia to be more dangerous than San Andreas, since the movement of Cascadia will entail not only an earthquake, but also a giant tsunami. In addition, 45 years ago, scientists did not know about the existence of this fault. Therefore, the United States is not ready for such destructive events. The authorities of the country began to conduct large-scale exercises in case of a disaster in the Cascadia subduction zone. FEMA plans to hold them in the future.

New Madrid Fault

The north of the US state of Alabama is located in the zone of influence of the New Madrid fault. This fault is about 20 times the size of San Andreas. Last earthquake in this seismic zone occurred in 1812. However, in Lately activity along the fault line began to increase.

“I think most people know that an earthquake can happen here, but they just can't remember. last time when they were shaking," said Gary Patterson, a geologist at the Memphis Center for Earthquake Research and Information. Earthquakes that occurred earlier in this region were felt at a distance of 1,000 to 1,200 kilometers from the epicenter, the scientist noted.

According to the FEMA scenario, more than 900 people in Alabama could be affected by an earthquake of magnitude 7.7. As a whole across the USA 86 thousand inhabitants can suffer. Computer simulations based on the 1812 earthquake have shown that a repeat of the same seismic event is possible in the next 50 years.

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 the geysers has risen, the 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, built on computer simulation. 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 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, of particular concern are areas at the boundaries of tectonic plates, which long time remain "mute" 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 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 sections of the fault.

To understand their arguments, it is worth first describing the nature of San Andreas and mechanical behavior. earth's crust throughout its entire 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, and 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 shift 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 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.

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 with terrifying integrity.