Geological map of faults in the earth's crust. Living faults in the earth's crust

Geological fault, or gap- violation of the continuity of rocks, without displacement (crack) or with displacement of rocks along the surface of the rupture. The faults prove relative motion earth masses. Major faults earth's crust are the result of shifting tectonic plates at their junctions. Active fault zones often experience earthquakes as a result of the release of energy during rapid sliding along a fault line. Since most often faults do not consist of a single crack or rupture, but of a structural zone of similar tectonic deformations that are associated with the fault plane, such zones are called fault zones.

The two sides of a non-vertical fault are called hanging side And sole(or recumbent side) - by definition, the first occurs above and the second below the fault line. This terminology comes from the mining industry.

Types of faults

Geological faults are divided into three main groups depending on the direction of movement. A fault in which the main direction of movement occurs in the vertical plane is called fault with dip displacement; if in the horizontal plane - then shift. If the displacement occurs in both planes, then such a displacement is called fault-shift. In any case, the name applies to the direction of movement of the fault, and not to the present orientation, which may have been changed by local or regional folds or tilts.

Fault with dip offset

Faults with dip displacement are divided into discharges, reverse faults And thrusts. Faults occur during crustal extension, when one block of the earth's crust (the hanging wall) sinks relative to another (the footwall). A section of the earth's crust that is lowered relative to the surrounding fault areas and located between them is called graben. If the section, on the contrary, is raised, then such a section is called handful. Discharges regional significance with a small angle is called breakdown, or peeling. Reverse faults occur in the opposite direction - in them the hanging wall moves upward relative to the base, while the angle of inclination of the crack exceeds 45°. During reverse faults, the earth's crust contracts. Another type of fault with dip displacement is thrust, in it the movement occurs similar to a reverse fault, but the angle of inclination of the crack does not exceed 45°. Thrusts usually form slopes, rifts and folds. As a result, tectonic nappes and clips are formed. A fault plane is the plane along which the rupture occurs.

Shifts

Fault rocks

All faults have a measurable thickness, which is calculated by the size of the deformed rocks, which determine the layer of the earth's crust where the rupture occurred, the type of rocks subjected to deformation and the presence of mineralization fluids in nature. A fault passing through different layers of the lithosphere will have various types rocks on a fault line. Long-term displacement along the dip leads to the overlapping of rocks with characteristics different levels earth's crust. This is especially noticeable in cases of failures or major thrust faults.

The main types of rocks at faults are the following:

• Cataclasite is a rock whose texture is due to the structureless fine-grained rock material.
• Mylonite is a shale metamorphic rock formed by the movement of rock masses along the surfaces of tectonic faults, by crushing, grinding and squeezing the minerals of the original rocks.
• Tectonic breccia is a rock consisting of acute-angled, unrounded rock fragments and cement connecting them. Formed as a result of crushing and mechanical abrasion of rocks in fault zones.
• Fault mud is a loose, clay-rich soft rock, in addition to ultrafine-grained catalytic material, which may have a planar textured pattern and contain< 30 % видимых фрагментов.
• Pseudotachylyte is an ultrafine-grained, glassy rock, usually black in color.

Faults are often geochemical barriers - therefore, accumulations of solid minerals are confined to them. They are also often insurmountable (due to the displacement of rocks) for brines, oil and gas, which contributes to the formation of their traps - deposits.

Indication of deep faults

Location deep faults determined and mapped (mapped) on the Earth's surface using interpretation satellite images, geophysical research methods - various types of seismic sounding of the earth's crust, magnetic surveys, gravimetric surveys. Geochemical methods are also often used - in particular, radon and helium surveys. Helium, as a product of the decay of radioactive elements, saturates top layer the earth's crust, seeps through cracks, rises into the atmosphere, and then into outer space. Such cracks, and especially the places where they intersect, have high concentrations of helium. This phenomenon was first established by a Russian geophysicist

Many of you - even those who only occasionally see quarries, road cuts or cliffs on the seashore - have noticed sudden changes rock structures. In some places you can see how rocks of one type abut rocks of a completely different type, separated from them by a narrow line of contact. In other places, strata of the same rock have undoubtedly experienced displacement, vertical or horizontal. Such drastic changes geological structure are called faults. In Fig. 1 clearly distinguishes the vertical displacement of rock layers along a fault exposed in the wall of the Corinth Canal in Greece.

The length of faults can vary from several meters to many kilometers. Working in the field, geologists find many tectonic boundaries in the structure of rocks, which they interpret as faults and plot on geological maps as solid or broken lines. The presence of such faults indicates that at some time in the past certain movements occurred along them. We now know that such movements can be either slow sliding, which does not produce any vibrations of the ground, or sharp tearing up, causing noticeable vibrations - earthquakes. In the previous chapter, we looked at one of the most famous examples of sharp movement along a fault - the rupture of the San Andreas Fault in April 1906. However, the trace of a rupture on the surface observed during most shallow earthquakes is much smaller in size, and the displacement is much smaller. In most earthquakes, the resulting rupture does not reach the surface and therefore cannot be directly seen.

Fractures found on the surface sometimes extend to considerable depths inside the outer shell of the Earth; this shell is called the earth's crust. It is a stone shell with a thickness of 5 to 40 km and is top part lithosphere.

It must be emphasized that along most faults plotted on geological maps, movements no longer occur*). The last displacement along a typical such fault could have occurred tens of thousands or even millions of years ago. The local stresses that caused the destruction of rocks in a given place on the Earth may have weakened long ago, and chemical processes, including water circulation, could heal the resulting ruptures, especially at depth. Such inactive faults do not become sources of earthquakes and, perhaps, never will.

Our main attention is, of course, drawn to active faults along which displacements of blocks of the earth's crust can occur. Many of these faults are located in fairly distinct tectonically active areas of the Earth, such as mid-ocean ridges and young mountain ranges. However, a sudden revival of faults can also occur far from areas with currently clearly visible tectonic activity *).

Geological analysis methods can be used to determine some properties of faults. For example, episodic movements along faults that have occurred in recent millennia leave traces in the relief such as depression lakes, lines of springs, and fresh fault ledges. Many topographic features of the San Andreas fault zone can be seen in Fig. Chapter 1 2. But it can be much more difficult to accurately establish the sequence and time of such movements. Some information of a chronological nature can be obtained from such facts as the displacement of overlying soils and young sedimentary deposits. Drilling trenches several meters deep across faults also proved effective means study of displacements. Even the smallest movements in the layers on either side of the trench can be mapped, and the time intervals between fault movements can be inferred from the age and properties of the rocks that were displaced (Fig. 2). Sometimes the actual time of movement can be estimated from the known age of buried organic material, say leaves or branches. Even on seabed With the help of modern geophysical methods, faults can be mapped quite accurately. On research vessels at sea they record sound waves, reflected from the layers of silt, and the resulting records show displacements of these layers, which can be considered faults.

1 - crack filled with clay, silt and sandy material; 2-layer A: thin grit of limestone-shell rocks - the youngest sediments of Lake Cahuilla; 3-massive light brown clays and silts containing rare remains of mollusks and thin, highly carbonated layers; 4-light gray-green carbonate silts with numerous shellfish; 5-foliate cross-bedded and massive clays, silts, sands, in places with lenses of pebbles, rare remains of mollusks everywhere; 6-geological boundaries (approximately drawn areas are shown with dashes); 7-cracks (dashed lines indicate the expected position).

Both on land and under ocean waters, displacements along faults can be divided into three types, as shown in Fig. 3. The discontinuity plane intersects horizontal surface soil along the

direction, going at some angle to the north. This angle is called the strike angle of the fault. The fault plane itself is usually not vertical and goes deep into the Earth at a certain angle. If the rocks on the side of the fault that hangs over the crack (they say: on the hanging side of the fault) move down and are lower than on the opposite side, then we have a fault. The dip angle of the fault varies from 0 to 90°. If the hanging side of the fault is displaced upward relative to the lower, overlying side, then such a fault is called a reverse fault. Reverse faults with low dip angles are called thrust faults. The faults that occur in the foci of earthquakes in the area of ​​ocean ridges are predominantly normal faults, and in deep-sea trenches many earthquakes associated with movements such as thrust faults occur.

Both faults and reverse faults are characterized by vertical displacements, which on the surface look like structural ledges; movement in both cases occurs along the dip (or uplift) of the fault plane. If, on the contrary, only horizontal displacements along strike, such faults are called strike-slip faults. It is useful to agree on some in simple terms, which would indicate the direction of the displacements. For example, in Fig. The 3 arrows on the shift diagram show that the movement was directed towards left side. It is not difficult to determine whether the shift was left- or right-sided. Imagine standing on one side of a fault and looking at the other side. If opposite side shifted from right to left, this is a left-sided (left) shift, but if from left to right, it’s a right-sided (right) shift. Of course, displacement along a fault can have both components: both along the dip and along the strike (such faults are called normal-slip or reverse-slip faults).

During an earthquake, serious damage can occur not only as a result of ground vibrations, but also as a result of the displacement along the fault itself, although this special kind seismic hazard has a very limited area distribution. This hazard can usually be avoided by obtaining timely (before construction) geological advice on the location of active faults. Areas on either side of an active fault are often left undeveloped and used for public recreation, golf courses, parking lots, roads, etc.

When planning land use, it is also necessary to take into account that in areas adjacent to an opened fault, the nature of destruction caused by the sliding and collapse of the soil depends on the type of fault. If the displacement occurs along the dip of the fault, then the appearance of the ledge is associated with destruction (due to local phenomena of sliding, cracking and collapse of the soil) in a fairly wide strip running along the fault itself. If displacement occurs along the strike of the fault, the zone of disturbance in the ground is usually much less wide, and buildings located only a few places from the fault may experience no damage at all.

Many people watched the disaster film “10.5 Points”. But not many people know that what is described in it can actually happen at any moment. The city of Taft, central California, is one of many cities that is in the zone of constant earthquakes.

At first glance, the streets of Taft are no different from the streets of any other city. 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 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.

Twelve tectonic plates, on which the continents and oceans of the Earth are located, are connected by a line running from San Francisco to the Gulf of California, which goes sixteen kilometers deep into the planet.

The usual thickness of these plates is about a hundred kilometers; they are located in constant movement, moving along the surface of the liquid inner mantle and colliding with each other monstrous strength when their location changes. If they crawl on top of each other, large ones rise into the sky mountain ranges, such as the Alps and Himalayas. However, the circumstances that gave rise to the San Andreas Fault are completely different.

Here are the edges of the North American (on which most of this continent rests) and the Pacific (which supports most of California coast) tectonic plates are like poorly fitted gear teeth that do not fit one on top of the other, but also 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.

The same thing strong earthquake in the United States over the past century occurred on April 18, 1906. Then the force of the shocks on the Richter scale was 8.3 points. The disaster then claimed 3,000 lives, and the city of San Francisco was engulfed in severe fires.

Between the two described above lie intermediate zones, whose activity, although not as destructive as in the castle zones, is nevertheless significant. The phenomenon of earthquake cyclicity is unique to this region. The city of Parkfield, located between San Francisco and Los Angeles, is in such 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.

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 developed, more advanced measuring instruments appeared, capable of constantly monitoring movements and pressure water masses below the earth's surface. For a number of years before 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 certain vibration forces earth's surface. 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.

The comparison of the Middle East problem with such a phenomenon as a tectonic shift, made by the Director of the Department of Information and Press of the Ministry of Foreign Affairs of the Russian Federation, Maria Zakharova, was very puzzling and even frightened almost all foreign television channels. Her statement was seen not only as a challenge, but also as a threat to NATO and the United States.

Apocalypse as such

For readers who haven't seen the movie San Andreas Fault, this article explains in detail what a tectonic shift is and how to apply this concept to a political scenario. today. The extent to which this phenomenon threatens humanity is explained even by the enormous interest that is observed in the world towards the possibility of an imminent apocalypse.

The reasons for its onset are considered to be lightly dormant supervolcanoes, and the third world war followed by nuclear winter, and, of course, tectonic shift. Humanity is so worried about its fate that even a simple comparison with this geological area from the mouth politician received a huge response in the world media.

About tramps

Geologists easily read the chronicles of centuries and even millennia. From them we know that sandy desert soils are stored in huge deposits in the south of England, the remains of ancient giant ferns have been discovered in Antarctica, and in Africa - obvious traces the glaciers that covered it. This suggests that geological epochs The climate also changed. Shift activated volcanic activity, the ash obscured the sun, rising into the upper atmosphere to for many years, the long winter has come. Ice Ages killed most of all life on Earth. For example, only bird species after last glaciation less than fifteen percent remain, and it is difficult to imagine that today's diversity is a pitiful remnant of its former splendor.

There are quite a few very different scientific explanations reasons global changes. One of them, the most widespread and most conclusive, says that the continents do not stand still. A small example clearly shows what a tectonic shift means. If you apply east South America to the west of Africa, they will fit together with virtually no gaps. This means that he did not always separate them Atlantic Ocean. There are many such examples. And the fact that America will face terrible tectonic shifts is not a threat from the lips of Maria Zakharova. This is what nature promises. And, since Hollywood has already flooded the cinema with many hundreds of films about the imminent end of the world, where they even go into action, it means that Americans fully anticipate and understand the impending danger.

Tectonic shift

The definition of this phenomenon was given long ago and precisely: it is a fracture of a single solid continental plate located under the earth’s crust. How do tectonic plate faults threaten humanity? The scenario is this: one, even a small fault will engulf the planet chain reaction. Melted glaciers will release the plates from the pressure of their enormous mass, the earth's crust will rise, and ocean water will pour into the depths of the faults. The magma under the crust is hot - about one thousand two hundred degrees Celsius. Steam with basalt dust and gas will be ejected from underground with enormous force and everywhere. Rainfalls will begin - unprecedented, akin to a flood. Volcanoes will wake up - all of them. After which an indescribable tsunami will sweep away everything from the face of the planet. There is enough time for the entire situation from the beginning of the fault to the volcanic eruptions; you can even run away if you find somewhere. After the tsunami begins, the earth will be empty within a matter of hours.

The continents we inhabit were formed two hundred million years ago, when Pangea, the hypercontinent, split apart. The scattered tramps "took root" for approximately equal distances from each other, but still they are drawn to each other. Scientists predict that in about fifty million years they will reunite. In the 70s of the last century, a model of the supposed movement of continents was created. It turns out that the Pacific plate is moving quite quickly towards the North American tectonic plate. The San Andreas tectonic shift threatens right at the junction of these two plates. Earthquakes are common there destructive force, which happened in San Francisco and Los Angeles just a hundred years ago. America is terribly afraid of geological disasters, which is why Maria Zakharova’s words were perceived as if Russia was threatening the United States with tectonic shifts. What exactly did the director of the department mean?

To the history of the issue

Of course, this was a warning about the threat, but “terrible tectonic shifts” were not promised from Russia (Zakharova quote). They will happen if the United States insists on replacing Syrian leader Assad, who is fighting the Islamic State. Then radical Islamists and terrorists, with whom America is already very familiar, will inevitably come to power. The events of Iraq in 2003 and Libya in 2011 (after the overthrow of Saddam Hussein and Muammar Gaddafi) speak for themselves. The Islamic State will inevitably grow and become much stronger. This is precisely what the Russian Foreign Ministry constantly signals. Then the rampant terrorism may well exceed the dangers that tectonic shifts bring with them. Zakharova was told exactly this, but the conclusions that followed were absolutely incorrect.

The Middle East did not gain stability in 2016, negative developments continue there: bloodshed in Syria, lack of stabilization in Libya, riots of the Kurdish autonomy in Iraq, the Yemen conflict has worsened, Saudi Arabian rebels have been inflicting increasingly serious blows on the economy and financial situation of the country for many years leading military operations, got involved in Middle Eastern conflicts. It is from the Middle East that all tectonic shifts in politics are coming. The situation is a crisis in all respects, and this crisis is rapidly expanding, chaos is growing, waves of refugees are sweeping Europe, creating a security threat and huge problems there. The year has ended, and it did not bring any solutions. If and last stronghold fight against terrorists - “dictator” Bashar Assad will lay down his arms, “tectonic shifts” of 2016 will sweep the whole world.

Methods of warfare

Daesh continues to build up its military potential, and, despite the beginning of the liberation of territories, the Iraqi army with its US and coalition supporters did not have an easy walk through the suburbs of Mosul. The threat of terrorism is not only not eliminated, it is growing, and therefore absolutely special, truly serious efforts global scale of forces united in this struggle for complete victory this evil. The level of US influence on the Middle East situation has decreased, and it has decreased quite significantly. The current administration is leaving, as if deliberately weakening the potential and capabilities of its own country in this region; it is now impossible to admit that the United States is the leading player in the Middle East. And the change of power there is taking place in an environment that itself is capable of starting tectonic shifts in America (and this is not about geological faults).

But Russia distinguished itself in the Middle East in 2016, significantly expanding the circle of partners, including Egypt, Israel and Bahrain, making progress in cooperation with Qatar, and agreeing with OPEC to limit the level of oil produced (even with Saudi Arabia managed to get along), normalized relations with Turkey. A new team has been formed to resolve the situation in Syria, ousting the United States from the region. These are Iran, Türkiye and Russia. The Russian Aerospace Forces are seriously helping Syrian army defeat terrorists. Aleppo liberated. All this is regarded by the world as purely Russian political victories. That is why Maria Zakharova spoke so brightly and colorfully about tectonic shifts. The loss of a partner like Bashar al-Assad will reduce these victories to zero. Moreover, until the Islamic State is completely exsanguinated, our diplomats see the current situation as quite precarious.

Crimea and the Middle East

To take a little break from daily life political problems, let's return to the issue of geological faults and continental plates, since more and more information appears every day, and from time to time it looks like a curiosity, despite all its reliability. Scientists different countries, studying geological layers deep in the earth's crust, have identified a shift in tectonic plates, as a result of which tectonic activity is observed in the Middle East and neighboring regions.

Full member Russian Academy Sciences Alexander Ipatov announced the latest reliable research results (including applied astronomy). Sensation: the Crimean peninsula is gradually moving closer to Russia. After all, the plate did not float towards Turkey or Greece, the tectonic shift of Crimea is geologically directed home. The meeting of the peninsula with the mainland, however, will not happen so soon; it will have to wait several tens of millions of years. But the republics have met together since 2014.

World politics and tectonic shifts in it

The results of the past year can be fully summed up only when the upcoming policy of the new United States administration - both in the Middle East and in the world in general - becomes clear. However, the contradictions between the Islamic world and Western countries They are unlikely to be eliminated soon, and the growth of xenophobia will most likely continue, which, of course, can poison the entire system of relations in both the Islamic and non-Islamic worlds. All year we have observed huge changes in world politics, which were quite akin to tectonic shifts in their significance.

First of all, we need to mention Brexit, which thoroughly shook the world, when Great Britain decided to leave the European Union. Then came the unexpectedly convincing victory of Donald Trump in the US presidential election, which not only no one had planned, but also did not allow the slightest thought about such a turn of events. If we add to this the significantly strengthened right and European countries(primarily in France and Germany), then the progress seems irreversible; in 2017 it is unlikely that they will stop their development.

Center of gravity

The value spectrum of the entire Western part of the world has shifted greatly, as right-wing conservative, populist and nationalist waves have made the palette of moods of society much more diverse, adding completely unexpected new tones. Protest sentiments appear even where they have never existed, in countries for which this is completely uncharacteristic. They write about what is starting in the United States, about the abrupt change of regime in the countries Western Europe. gradually becomes unpredictable, filled with new, never-before-happened events and phenomena that need to be comprehended.

The center of gravity of the entire world political system is clearly shifting. Intensifying Asian countries, rose exceptionally high specific gravity China and India. Therefore, the main intrigues of this tectonic shift in politics will most likely unfold in relations between China and the United States. The economic crisis that has gripped the world is also hard for the leading countries. The people of the United States are gripped by general disappointment in the policies of the ruling party. That is why the Republicans won such a convincing victory over the Democrats, won a majority of seats in the House of Representatives and increased their representation in the Senate.

Internal and external policy

Trump's victory is important not so much for domestic policy, how much for external. Israel is already clearly excited, China is concerned, the rest of Asia is upset, and Russia is speculating. A much tougher position towards China is quite possible - a weakening of the yuan until it is impossible to maintain its own currency. Support is very possible Afghan war. Republicans are also concerned about the country's missile defense deployment.

Congress received a significant strengthening of pro-Israeli forces: Senator from Illinois - Mark Kirk, majority leader of the lower house - Eric Cantor, now Tel Aviv can hope for a special political climate that will allow the resumption of negotiations with the Palestinian Authority. At the same time, pro-Israeli forces are feeling strong pressure from forces that are still unknown (however, everyone can guess which ones): on January 19, 2017, there were reports of mining of 28 Jewish centers in 17 US states, which, fortunately, was imaginary. But this is not the first warning. And at a certain moment, mining may not be false.

How will it end?

It seems to many that America’s stable position in the world has been shaken, and its global dominance has almost been lost. Is this true? The President of Russia is also very cautious in his assessments. Indeed, remember 2010, when WikiLeaks opened and made public tens of thousands of documentary letters from the American diplomatic post. It seemed - well, that’s it, the end of the power. But nothing happened to America. The allies, even when substituted in every possible way, were not lost. The enemies also remained in place, no new ones were added. One thing is surprising: no one thought to blame Moscow for these revelations, as happened after Donald Trump won the election.

Yes, Trump is different. He is significantly different from the previous president. But who knows what awaits Russia in connection with this choice? If you look from Moscow or some Skovorodin, the Republicans are seen as people who are more pragmatic and less dangerous for us than the defeated Democrats, who constantly committed minor and major mischief to the Russians. How different is Trump's team from Hillary Clinton's team? After thoughtful analysis, it becomes clear that the actions of both parties are unfolding on the same lithospheric platform. They are much more similar than seen from afar. Both teams intimidate the people with an external threat and paint a picture of various foreign intrigues. Freedom and democracy are respected by some, prestige and economics by others, but both are threatened external forces, in any case, the nation is in danger. Hillary did not like global populism and Russia, and Trump does not like transnational corporations, Mexico, China and developing countries. Tectonic shift inevitable in politics. This is probably why our diplomats are so cautious in their assessments and forecasts.

Today, there are two most likely hypotheses for a tectonic fault that will lead to the end of our civilization. And the fact that the earth's masses move and the Earth is constantly changing - not a single reasonable person won't deny it. Although lately tectonic activity has been very low, there is a high probability that this will change soon.

Iceland.

Giant rifts are ruptures in the earth's crust that form at the boundary of slowly diverging tectonic plates - the North American and Eurasian plates. The plates are moving apart at a rate of about 7 mm per year, so that over the past 10 thousand years the valley has widened by 70 meters and settled by 40.

The San Andreas Fault, which is in motion, is indicative. It is considered one of the most dangerous in the world. Seismologists have noticed that ups and downs occur there. I.

What movements are characteristic of the San Andreas Fault?

Although these movements are small enough that they will not be noticed by most people living along the fault, the researchers note that they are consistent and constant. Every 200 kilometers of the fault moves by 2 mm per year. Movements occur up or down. These changes were detected using GPS measurements.

These movements were undoubtedly caused by the chaotic, jerky movements of the Pacific and North American tectonic plates. Small surges of accumulated stress cause the ground around the fault to rise and fall. Consequently, the Los Angeles Basin is sinking while the San Bernardino portion is rising, and at the same rate.

Releasing pressure E

These minor changes do not pose any immediate danger to the population. But they do demonstrate how dynamic and active the fault is. While the movement relieves pressure in San Andreas, it is not enough to reduce the next blow.

Massive sections of the fault have shifted little over the past 150 years, while other sections have been accumulating pressure for more than three centuries.

Once an earthquake occurs, all this energy is released. Understanding how a fault behaves each time it dips and rises, releasing pressure, helps geologists estimate how the next earthquake that might hit the area will impact the surrounding region.