Zones with seismic activity, where earthquakes most often occur, are called seismic belts. In such a place there is increased mobility of lithospheric plates, which is the cause of volcanic activity. Scientists claim that 95% of earthquakes occur in special seismic zones.
There are two huge seismic belts on Earth, which have spread over thousands of kilometers along the bottom of the World Ocean and land. These are the meridional Pacific and latitudinal Mediterranean-Trans-Asian.
In developing areas, seismic hazard is usually much higher. The greatest relative vulnerabilities were recorded in Iran and Afghanistan; also in Turkey, Russian Federation, Armenia and Guinea. Every year, about a million earthquakes are observed in seismographs, of which 99% However, up to 100 earthquakes can occur each year, which can cause serious damage. It is estimated that about 1,000 people die each year due to earthquakes.
The devices used to graphically measure seismic movements are called seismographs and a graphical record that records the amplitude and duration of the seismic wave of the seismogram. Earthquakes are measured based on intensity and magnitude parameters.
The Pacific Latitudinal Belt encircles the Pacific Ocean to Indonesia. Over 80% of all earthquakes on the planet occur in its zone. This belt passes through the Aleutian Islands, covers the western coast of America, both North and South, and reaches the Japanese Islands and New Guinea. The Pacific belt has four branches - western, northern, eastern and southern. The latter has not been studied enough. Seismic activity is felt in these places, which subsequently leads to natural disasters.
Measures intensity, has 12 degrees and indicates the force with which an earthquake is felt at a point on the Earth's surface from observing the damage it causes. It measures magnitude, has 9 degrees, and expresses the energy released by an earthquake as recorded in seismograms. The measurement scale is logarithmic, which means it is saturated at the extremes and never reaches a value of 9. Richter scale. . This presents great difficulty because it is very difficult to determine when, where or with what magnitude an earthquake will occur.
Currently, there are no effective systems for timely warning the population that an earthquake is imminent. Seismic prediction is based on two fields. Large earthquakes often recur at more or less fixed intervals, so studying periods of seismic quiet can help predict the occurrence of high-intensity earthquakes, since areas with a large quiet interval are areas at greater risk of having a lot of time building up tension. Seismic precursor analysis: changes in the physical properties of the area caused by the accumulation of stress around a fracture. These changes may be: Levels, heights or depressions of several centimeters in the terrain. A change in the local magnetic field of a few parts per thousand. increase the amount of radon gas in groundwater to a value that triples the original. A decrease in the relationship between the speed of the primary and secondary waves in small earthquakes, which often occur in areas of high seismic activity, is considered a precursor signal of a large earthquake that is imminent. As the number of local microseismic events that precede large earthquakes increases. Monitor the movement of active faults using specific monitoring devices. 95% of earthquakes are caused by the movement of lithospheric plates, which move at a speed of 1-10 cm per year. Faults located within the plates move at a certain frequency and suddenly release stored energy every certain number of years. Some animals can predict an earthquake with a certain expectation and manifest this through changes in their behavior.
The beginning of this seismic belt is in the Mediterranean Sea. It passes through the mountain ranges of Southern Europe, through North Africa and Asia Minor, and reaches the Himalayan mountains. The most active zones in this belt are:
As for underwater activity, it has been recorded in the Indian and Atlantic oceans, reaching the southwest of Antarctica.
This is the basic standard for seismic zones and aims to reduce the population's exposure and vulnerability to the effects of earthquakes. You should try to build without changing too much of the local topography and avoiding population concentrations by leaving wide spaces between buildings. Design with ductile materials that can deform to absorb vibrations without breaking. Design with lightweight materials that reduce vibration inertia, which contribute to the resonant effect. In this case, wooden buildings, being lightweight, are resistant to vibrations, but are more vulnerable to fires that can be caused by an earthquake. Pyramidal and symmetrical type buildings: this type of structure has better behavior against wave amplification. Let's consider the depth and absorbing basis of shock waves during construction. Spatial planning measures to avoid significant population densities in high-risk areas. Require that they be built a significant distance from active faults. Limit land use on land prone to suffering. liquefaction processes. Creation of seismic risk maps. Civil protection measures to inform and warn the population and evacuate if necessary. Inform the public about its consequences.
Seismic waves are flows that originate from an artificial explosion or earthquake source. Body waves are powerful and move underground, but vibrations are also felt on the surface. They are very fast and move in gaseous, liquid and solid media. Their activity is somewhat reminiscent of sound waves. Among them there are transverse waves or secondary ones, which have a slightly slower movement.
Rarely, earthquakes can occur as induced hazards, since in most cases earthquakes are generated naturally by the release of energy along fault lines. However, in very specific cases, earthquakes have been produced: mining operations involving explosives, nuclear explosions, hydrocarbon extraction, injection of fluids into the subsurface, or filling of large reservoirs have resulted in a sudden change in interstitial pressure and displacement of rocks, which has created pressure on existing fractures and caused certain seismic movements.
Surface waves are active on the surface of the earth's crust. Their movement resembles the movement of waves on water. They have destructive power, and the vibrations from their action are well felt. Among the surface waves there are especially destructive ones that can push rocks apart.
Volcanoes shed lava, which is molten rock formed up to 100 km away. Mass and density of the Earth. To calculate mass we resort to the law of universal gravitation. If we compare forces. If we consider as an approximation that the Earth is a perfect sphere, its volume will be.
This density value contrasts with the average density of the rocks that make up the continents, which. Behavior of seismic waves. Earthquakes occur when stresses built up by the deformation of the Earth's layers are suddenly released. They occur when large masses of earth are destroyed or subsequently displaced. These fractures are flaws. Masses of rocks that have been subjected to gigantic forces are destroyed, materials are rearranged and enormous energies are released that cause the Earth to tremble.
Thus, there are seismic zones on the surface of the earth. Based on the nature of their location, scientists have identified two belts - the Pacific and the Mediterranean-Trans-Asian. In the places where they lie, the most seismically active points have been identified, where volcanic eruptions and earthquakes often occur.
The main seismic belts are the Pacific and Mediterranean-Trans-Asian. They encircle a significant land area of our planet and extend for a long time. However, we must not forget about such a phenomenon as secondary seismic belts. Three such zones can be distinguished:
Its starting point is located at different depths, the deepest being up to 700 kilometers. They are especially common near the edges of tectonic plates. About a million earthquakes occur each year, although most are of such low intensity that they go unnoticed.
Here you can see a graph of how exploration of the Earth's interior is done using the delay time between the arrival of waves at a particular location. The source of an earthquake can be located using the time it takes for seismic waves to travel outward from the epicenter, the fault fault point.
Due to the movement of lithospheric plates, phenomena such as earthquakes, tsunamis and floods occur in these zones. In this regard, nearby territories - continents and islands - are prone to natural disasters.
Scientists discovered a seismic zone in the Atlantic Ocean in 1950. This area starts from the coast of Greenland, passes close to the Mid-Atlantic submarine ridge, and ends in the Tristan da Cunha archipelago. Seismic activity here is explained by young faults of the Seredinny Range, since the movements of lithospheric plates are still continuing here.
Density increases with depth, but compressibility increases to a greater extent. Density and speed of spread are inversely proportional. - Denser materials require more energy to vibrate and therefore slow down the waves much more.
For their part, stiffer media vibrate more efficiently, so that transmission through them is very rapid, and in liquids whose stiffness is zero, the absence of fixed positions for the particles prevents vibrations. Therefore, secondary seismic waves, which are transmitted by vibrations of particles relative to fixed positions, are not transmitted in liquids; primaries in which vibration is easier if they do so, albeit at a reduced speed.
The seismic strip in the Indian Ocean extends from the Arabian Peninsula to the south, and almost reaches Antarctica. The seismic area here is associated with the Middle Indian Ridge. Mild earthquakes and volcanic eruptions under water occur here; the foci are not located deep. This occurs due to several tectonic faults.
As with every wave that varies in speed, the trajectories are curved, allowing earthquake waves not very far back to the surface before draining their energy. The speed of propagation and trajectory of waves changes with depth. Every change in speed causes a change in the direction of the wave.
A discontinuity is a surface separating two layers of different characteristics, and therefore their existence is caused by sudden changes in wave speed. When studying the direction of propagation, it is confirmed that shadow zones exist in those places where earthquake waves that are between 103º and 143º are not received.
Seismicity is observed in the Arctic zone. Earthquakes, eruptions of mud volcanoes, as well as various destructive processes occur here. Experts are monitoring the main earthquake sources in the region. Some people believe that there is very little seismic activity here, but this is not true. When planning any activity here, you always need to stay on alert and be prepared for various seismic phenomena.
Other indirect data is temperature. Residual heat Disintegration of radioactive elements. . Mines and soundings reflect how temperature increases with depth. It allows an average of 3º every 100 m, or what is the same, 30º per km. These are small planetary bodies that fall to the Earth's surface when they cross their orbit. Most of them are grouped together to form an asteroid belt that orbits between Mars and Jupiter, so they would be the same age as the solar system.
Following this reasoning, they must have had very similar origins, so their composition is studied on the assumption that it is very similar to his. It was discovered that, depending on their composition, there are three types of meteorites: -Condrites: It is believed that the mixture of minerals, chondrites, peridotites is similar to the mantle. They make up 86% of the total. -Achondrites: make up 9% and have a composition similar to basalt. Siderites represent 4%, formed by iron and nickel.
The areas of the most powerful and frequent earthquakes form two seismic belts on the planet: latitudinal - Mediterranean-Trans-Asian - and meridional - framing the Pacific Ocean. In Fig. Figure 20 shows the location of earthquake epicenters. The Mediterranean-Trans-Asian belt includes the Mediterranean Sea and the surrounding mountain structures of Southern Europe, North Africa, Asia Minor, as well as the Caucasus, Iran, most of Central Asia, the Hindu Kush, Kuen Lun and the Himalayas.
Latest additions. It has nothing to do with fun: there are office windows that shatter into pieces, trains that get blown up, and cars falling off bridges that they give up. This is the catastrophic scenario described in a 300-page comic brochure on earthquake preparedness published by the Tokyo Area Government. The book opens with an important warning: According to experts, there is a 70 percent chance that within thirty years an earthquake will hit the Tokyo metropolitan area, home to 36 million people, directly. It's a race between us and an earthquake.
The Pacific Rim includes mountain structures and deep-sea trenches bordering the Pacific Ocean and the garlands of islands in the western Pacific and Indonesia.
The Earth's seismic activity zones coincide with active zones of mountain building and volcanism. The three main forms of manifestation of the internal forces of the planet - volcanism, the emergence of mountain ranges and earthquakes - are spatially associated with the same zones of the earth's crust - the Mediterranean-Trans-Asian and Pacific.
More than 80% of all earthquakes, including catastrophic ones, occur within the Pacific belt. A large number of earthquakes with subcrustal impact centers are concentrated here. About 15% of the total number of earthquakes is associated with the Mediterranean-Trans-Asian belt. Many earthquakes with intermediate focal depths occur here, and destructive earthquakes are also quite frequent.
Secondary zones and areas of seismicity are the Atlantic Ocean, the western Indian Ocean, and the Arctic regions. They account for less than 5% of all earthquakes.
The amount of seismic energy released in different active belts and zones is not the same. About 80% of the Earth's seismic energy is released in the Pacific belt and its branches, that is, where volcanic activity was and is most intense. More than 15% of the energy is released in the Mediterranean-Trans-Asian belt and less than 5% in other seismic zones and areas.
The eastern branch of the Pacific seismic belt, encircling the entire vast expanse of the Pacific Ocean, begins on the eastern coasts of Kamchatka, passes through the Aleutian Islands and the western coasts of North and South America and ends with the South Antilles loop, running from the southern tip of South America through the Folkleid Islands and the island of South Georgia . In the equatorial region, the Caribbean, or Antilles, loop branches off from the eastern branch of the Pacific seismic belt.
The most intense seismicity is in the northern part of the Pacific branch, where impacts with a force of up to 0.79 X 10 26 ergs occur, as well as the seismicity of its Californian branch. Within Central and South America, seismicity is somewhat less significant, although a large number of subcrustal impacts of varying depths have been recorded there.
The western branch of the Pacific belt stretches along Kamchatka and the Kuril Islands to Japan, where it, in turn, is divided into two branches - western and eastern. The western one goes through the Ryu-kyu Islands, Taiwan and the Philippines, and the eastern one goes through the Bonin Islands to the Mariana Islands. In the area of the Mariana Islands, subcrustal earthquakes with intermediate focal depths are very frequent.
The western branch from the Philippines heads to the Moluccas, goes around the Banda Sea and through the Sunda and Nicobar Islands stretches to the Andraman archipelago, apparently connecting through Burma with the Mediterranean-Trans-Asian belt.
The eastern branch from the island of Guam goes through the Pallau Islands to the western tip of New Guinea. There it turns sharply to the east and runs along the northern coast of New Guinea, the Solomon Islands, the New Hebrides and the Fiji Islands to the Tonga Archipelago, where it turns sharply south, stretching along the Tonga Trench, the Kermadec Trench and New Zealand. South of New Zealand it makes a sharp loop to the west and then goes east through Macquarie Island to the South Pacific Ocean. Information about the seismicity of the South Pacific Ocean is still insufficient, but it can be assumed that the South Pacific seismic zone is connected through Easter Island to the South American zone.
Within the western branch of the Pacific seismic belt, a significant number of subcrustal earthquakes have been recorded. A strip of deep sources runs under the bottom of the Sea of Okhotsk along the Kuril and Japanese Islands to Manchuria, then turns almost at a right angle to the southeast and, crossing the Sea of Japan and Southern Japan, goes to the Mariana Islands.
The second line of frequent subcrustal earthquakes occurs in the area of the Tonga and Kermadec deep-sea basins. A significant number of deep-focus strikes are also recorded within the Java Sea and the Banda Sea north of the Lesser Sunda Islands.
The Mediterranean-Trans-Asian seismic belt in the west includes an area of young Mediterranean subsidence ovals. From the north it is limited by the southern tip of the Alps. The Alps themselves, as well as the Carpathians, are less seismic. The active zone covers the Apennines and Sicily and extends through the Balkans, the islands of the Aegean Sea, Crete and Cyprus into Asia Minor. The Romanian node of this zone is active, in which strong earthquakes with a focal depth of up to 150 km have repeatedly occurred. To the east, the active zone of the belt expands, covers Iran and Baluchistan and, in the form of a wide strip, stretches further east to Burma.
Strong impacts with focal depths of up to 300 km are often observed in the Hindu Kush.
The seismic zone of the Atlantic Ocean begins in the Greenland Sea, through the island of Jan Mayen and Iceland it goes south along the Mid-Atlantic underwater ridge and is lost at the Tristan da Cunha islands. This zone occurs in the equatorial part, but strong impacts are rare here.
The seismic zone of the western Indian Ocean stretches across the Arabian Peninsula and goes south and then southwest along the ocean floor along the seamount to Antarctica. Strong impacts seem to be rare here, but it should be borne in mind that this entire zone has not yet been sufficiently studied. An inland seismic zone runs along the eastern coast of Africa, confined to a strip of East African grabens.
Small earthquakes with shallow sources are observed within the Arctic zone. They occur quite often, but are not always recorded due to the weak intensity of the tremors and the great distance from seismic stations.
The outlines of the Earth's seismic belts are peculiar and mysterious (Fig. 21). They seem to border more stable blocks of the earth's crust - ancient platforms, but sometimes penetrate into them. Of course, seismic belts are associated with zones of giant crustal faults - ancient and younger. But why did these fault zones form where they are now? This question cannot yet be answered. The mystery is hidden in the depths of the planet.
The Earth's seismic belts are lines along which the boundaries between lithospheric plates pass. If the plates move towards each other, then mountains form at the junctions (such areas are also called mountain-building zones). If the lithospheric plates diverge, then faults appear in these places. Naturally, processes such as the convergence and divergence of lithospheric plates do not remain without consequences - about 95% of all earthquakes and volcanic eruptions occur in these areas. That is why they are called seismic (from the Greek seismos - to shake).
It is customary to distinguish two main seismic belts: the latitudinal Mediterranean-Trans-Asian and the meridional Pacific, perpendicular to it. The vast majority of all earthquakes occur in these two areas. If you look at the seismic hazard map, it becomes clearly visible that the zones highlighted in red and burgundy are located precisely at the location of these two belts. They extend for thousands of kilometers, circling the globe, on land and under water.
Almost 80% of all earthquakes and volcanic eruptions occur in the Pacific Seismic Belt, otherwise known as the Pacific Ring of Fire. This seismic zone really, as if in a ring, envelops almost the entire Pacific Ocean. There are two branches of this belt - Eastern and Western.
The eastern branch starts from the shores of Kamchatka and goes through the Aleutian Islands, passes through the entire western coast of North and South America and ends in the South Antilles loop. In this area, most powerful earthquakes occur on the California peninsula, which determines the architecture of cities such as Los Angeles and San Francisco - houses predominate there one or two stories high with the occasional multi-story building, mainly in the central parts of the cities.
The western branch of the Pacific Ring of Fire stretches from Kamchatka through the Kuril Islands, Japan and the Philippines, covers Indonesia and, arcing around Australia, through New Zealand reaches Antarctica itself. This area experiences many powerful underwater earthquakes, often leading to catastrophic tsunamis. Island countries such as Japan, Indonesia, Sri Lanka, etc. suffer the most from earthquakes and tsunamis in this region.
The Mediterranean-Trans-Asian Belt, as its name suggests, extends across the entire Mediterranean Sea, including the southern European, northern African and Middle Eastern regions. Then it stretches across almost all of Asia, along the ridges of the Caucasus and Iran to the Himalayas, to Myanmar and Thailand, where, according to some scientists, it connects with the seismic Pacific zone.
According to seismologists, this belt accounts for about 15% of the world's earthquakes, while the most active zones of the Mediterranean-Trans-Asian belt are considered to be the Romanian Carpathians, Iran and eastern Pakistan.
There are also secondary zones of seismic activity. They are considered secondary because they account for only 5% of all earthquakes on our planet. The seismic belt of the Atlantic Ocean begins off the coast of Greenland, stretches along the entire Atlantic and finds its end near the islands of Tristan da Cunha. There are no strong earthquakes here, and due to the remoteness of this zone from the continents, tremors in this belt do not cause destruction.
The Western Indian Ocean is also characterized by its own seismic zone, and although it is quite large in length (its southern end reaches as far as Antarctica), earthquakes here are not too strong, and their foci are located shallow underground. There is also a seismic zone in the Arctic, but due to the almost complete desolation of these places, as well as due to the low power of tremors, earthquakes in this region do not have a particular impact on people’s lives.
Since the Pacific Ring of Fire accounts for up to 80% of all earthquakes, the main cataclysms in terms of their power and destructiveness occurred in this region. First of all, it is worth mentioning Japan, which has repeatedly become a victim of severe earthquakes. The most destructive, although not the strongest in terms of the magnitude of its fluctuations, was the earthquake of 1923, which is called the Great Kanto Earthquake. According to various estimates, 174 thousand people died during and from the consequences of this disaster, another 545 thousand were never found, the total number of victims is estimated at 4 million people. The most powerful Japanese earthquake (with a magnitude of 9.0 to 9.1) was the famous disaster of 2011, when a powerful tsunami caused by underwater tremors off the coast of Japan caused destruction in coastal cities, and a fire at a petrochemical complex in the city of Sendai and an accident at The Fokushima-1 nuclear power plant caused enormous damage to both the economy of the country itself and the environment of the whole world.
The most powerful Of all the documented earthquakes, the Great Chilean earthquake with a magnitude of up to 9.5, which occurred in 1960, is considered (if you look at the map, it becomes clear that it also occurred in the region of the Pacific seismic belt). The disaster that claimed the largest number of lives in the 21st century was the 2004 Indian Ocean earthquake, when a powerful tsunami, which was its consequence, claimed almost 300 thousand lives from almost 20 countries. On the map, the earthquake zone refers to the western tip of the Pacific Rim.
Many large and destructive earthquakes also occurred in the Mediterranean-Trans-Asian seismic belt. One of these is the 1976 Tangshan earthquake, when according to official Chinese data alone, 242,419 people died, but according to some sources, the number of victims exceeds 655 thousand, which makes this earthquake one of the deadliest in human history.
There are special zones of increased seismic activity on Earth, where earthquakes constantly occur. Why is this happening? Why do earthquakes occur more often in mountainous areas and very rarely in deserts? Why do earthquakes occur constantly in the Pacific Ocean, generating tsunamis of varying degrees of danger, but we have heard almost nothing about earthquakes in the Arctic Ocean. It's all about the seismic belts of the earth.
The earth's seismic belts are places where the planet's lithospheric plates come into contact with each other. In these zones, where the Earth's seismic belts are formed, there is increased mobility of the earth's crust and volcanic activity caused by the process of mountain building, which lasts for millennia.
The length of these belts is incredibly large - the belts stretch for thousands of kilometers.
There are two large seismic belts on the planet: the Mediterranean-Trans-Asian and the Pacific.
Rice. 1. Seismic belts of the Earth.
Mediterranean-Trans-Asian The belt originates off the coast of the Persian Gulf and ends in the middle of the Atlantic Ocean. This belt is also called the latitudinal belt, since it runs parallel to the equator.
Pacific belt– meridional, it stretches perpendicular to the Mediterranean-Trans-Asian belt. It is along the line of this belt that a huge number of active volcanoes are located, most of whose eruptions occur under the water column of the Pacific Ocean itself.
If you draw the Earth's seismic belts on a contour map, you will get an interesting and mysterious picture. The belts seem to border the ancient platforms of the Earth, and sometimes penetrate into them. They are associated with giant faults in the earth's crust, both ancient and younger.
The Earth's latitudinal seismic belt passes through the Mediterranean Sea and all the adjacent European mountain ranges located in the south of the continent. It stretches through the mountains of Asia Minor and North Africa, reaches the mountain ranges of the Caucasus and Iran, and runs through all of Central Asia and the Hindu Kush straight to Koel Lun and the Himalayas.
In this belt, the most active seismic zones are the Carpathian Mountains, located in Romania, all of Iran and Baluchistan. From Baluchistan the earthquake zone stretches to Burma.
Fig.2. Mediterranean-Trans-Asian seismic belt
This belt has active seismic zones, which are located not only on land, but also in the waters of two oceans: the Atlantic and Indian. This belt also partially covers the Arctic Ocean. The seismic zone of the entire Atlantic passes through the Greenland Sea and Spain.
The most active seismic zone of the latitudinal belt occurs at the bottom of the Indian Ocean, passes through the Arabian Peninsula and stretches to the very south and southwest of Antarctica.
But, no matter how dangerous the latitudinal seismic belt is, the majority of all earthquakes (about 80%) that occur on our planet occur in the Pacific belt of seismic activity. This belt runs along the bottom of the Pacific Ocean, along all the mountain ranges encircling this largest ocean on Earth, and captures the islands located in it, including Indonesia.
Fig.3. Pacific seismic belt.
The largest part of this belt is the Eastern one. It originates in Kamchatka, stretches through the Aleutian Islands and the western coastal zones of North and South America straight to the South Antilles loop.
The eastern branch is unpredictable and little studied. It is full of sharp and twisting turns.
The northern part of the belt is the most seismically active, which is constantly felt by residents of California, as well as Central and South America.
The western part of the meridional belt originates in Kamchatka, stretches to Japan and beyond.
It is no secret that during earthquakes, waves from vibrations of the earth's crust can reach remote areas that are generally considered safe with regard to seismic activity. In some places, the echoes of earthquakes are not felt at all, and in others they reach several points on the Richter scale.
Fig.4. Map of Earth's seismic activity.
Basically, these zones, sensitive to vibrations of the earth's crust, are located under the water column of the World Ocean. The planet's secondary seismic belts are located in the waters of the Atlantic, Pacific Ocean, Indian Ocean and the Arctic. Most of the secondary belts are located in the eastern part of the planet, so these belts stretch from the Philippines, gradually descending to Antarctica. The echoes of tremors can still be felt in the Pacific Ocean, but in the Atlantic there is almost always a seismically calm zone.
So, on Earth, earthquakes do not occur in random places. It is possible to predict the seismic activity of the earth's crust, since the bulk of earthquakes occur in special zones called seismic belts of the earth. There are only two of them on our planet: the Latitudinal Mediterranean-Trans-Asian seismic belt, which stretches parallel to the Equator, and the meridional Pacific seismic belt, located perpendicular to the latitudinal one.
The Earth's seismic belts are zones where the lithospheric plates that make up our planet come into contact with each other. The main characteristic of such areas is increased mobility, which can be expressed in frequent earthquakes, as well as in the presence of active volcanoes, which tend to erupt from time to time. Typically, such regions of the Earth stretch for thousands of miles in length. A large fault can be traced throughout this entire distance. If such a ridge is located on the ocean floor, it looks like a mid-oceanic trench.
According to generally accepted geographical theory, there are now two largest seismic belts on the planet. These include one latitudinal, that is, located along the equator, and the second is meridian, respectively, perpendicular to the previous one. The first is called the Mediterranean-Trans-Asian and it originates approximately in the Persian Gulf, and the extreme point reaches the middle of the Atlantic Ocean. The second is called the Pacific meridional, and it passes in full accordance with its name. It is in these areas that the greatest seismic activity is observed. Mountain formations have their place here, and also constantly. If these seismic belts of the Earth are viewed on a world map, it becomes clear that most eruptions occur precisely in the underwater part of our planet.
It is important to know that 80 percent of all earthquakes and volcanic eruptions occur in the Pacific Mountain Range. Most of it is located under salt waters, but it also affects some parts of the land. For example, precisely because of the splitting of the earth's rock, earthquakes constantly occur, which often lead to a large number of human casualties. Further, this giant ridge includes smaller seismic belts of the Earth. So, it includes Kamchatka. It affects the western coast of the entire American continent and ends right on the South Antilles Loop. That is why all residential regions that are located along this line constantly experience more or less strong earth tremors. Among the most popular giant cities that are located in this unstable area is Los Angeles.
Now let's look at the zones of so-called secondary earthquakes, or secondary seismicity. All of them are quite densely located within our planet, but in some places the echoes are not audible at all, while in other regions the tremors reach almost a maximum. But it is worth noting that this situation is characteristic only of those lands that are under the waters of the World Ocean. The Earth's secondary seismic belts are concentrated in the waters of the Atlantic, in the Pacific Ocean, as well as in the Arctic and in some areas of the Indian Ocean. It is interesting that strong tremors, as a rule, occur precisely in the eastern part of all earthly waters, that is, the “Earth breathes” in the Philippines, gradually descending lower to Antarctica. To some extent, the focus of these impacts also extends to the waters of the Pacific Ocean, but the Atlantic is almost always calm.
As mentioned above, the Earth’s seismic belts are formed precisely at the junctions of the largest lithospheric plates. The largest of these is the meridian Pacific ridge, along the entire length of which there are a huge number of mountain elevations. As a rule, the source of shocks that causes tremors in this natural zone is subcrustal, so they spread over very long distances. The most seismically active branch of the meridian ridge is its northern part. Extremely high impacts are observed here, which often reach the California coast. It is for this reason that the number of skyscrapers that are built in a given area is always kept to a minimum. Please note that cities such as San Francisco and Los Angeles are, in general, one-story. High-rise buildings were built only in the city center. Heading lower, to the south, the seismicity of this branch decreases. On the west coast, the tremors are no longer as strong as in the North, but subcortical foci are still noted there.
The names of the Earth's seismic belts, which are branches of the main meridian Pacific Ridge, are directly related to their geographical location. One of the branches is Eastern. It originates off the coast of Kamchatka, runs along the Aleutian Islands, then goes around the entire American continent and ends at This zone is not catastrophically seismic, and the tremors that form within its boundaries are small. It is only worth noting that in the region of the equator a branch leaves from it to the East. The Caribbean Sea and all the island states that are located here are already in the Antilles seismic loop zone. This region previously experienced many earthquakes, which brought many disasters, but these days the Earth has “calmed down”, and the tremors, which are heard and felt in all resorts of the Caribbean, do not pose any danger to life.
If we look at the Earth’s seismic belts on a map, it turns out that the eastern branch of the Pacific Ridge runs along the westernmost land coast of our planet, that is, along America. The western branch of the same seismic belt begins at the Kuril Islands, passes through Japan, and then divides into two others. It is strange that the names of these seismic zones were chosen exactly the opposite. By the way, the two branches into which this strip is divided also have the names “Western” and “Eastern,” but this time their geographical affiliation coincides with generally accepted rules. The eastern one goes through New Guinea to New Zealand. Quite strong tremors can be traced in this area, often of a destructive nature. The eastern branch covers the shores of the Philippine Islands, the southern islands of Thailand, as well as Burma, and finally connects with the Mediterranean-Trans-Asian belt.
Now let's look at the lithospheric region that is located closer to our region. As you already understand, the name of the seismic belts of our planet depends on their location, and in this case, the Mediterranean-Trans-Asian ridge is proof of this. Within its extent are the Alps, Carpathians, Apennines and islands located in the Mediterranean Sea. The greatest seismic activity occurs in the Romanian node, where strong tremors are observed quite often. Moving to the East, this belt covers the lands of Balochistan, Iran and ends in Burma. However, the total percentage of seismic activity that occurs in this area is only 15. Therefore, this region is quite safe and calm.
The areas of the most powerful and frequent earthquakes form two seismic belts on the planet: latitudinal - Mediterranean-Trans-Asian - and meridional - framing the Pacific Ocean. In Fig. Figure 20 shows the location of earthquake epicenters. The Mediterranean-Trans-Asian belt includes the Mediterranean Sea and the surrounding mountain structures of Southern Europe, North Africa, Asia Minor, as well as the Caucasus, Iran, most of Central Asia, the Hindu Kush, Kuen Lun and the Himalayas.
The Pacific Rim includes mountain structures and deep-sea trenches bordering the Pacific Ocean and the garlands of islands in the western Pacific and Indonesia.
The Earth's seismic activity zones coincide with active zones of mountain building and volcanism. The three main forms of manifestation of the internal forces of the planet - volcanism, the emergence of mountain ranges and earthquakes - are spatially associated with the same zones of the earth's crust - the Mediterranean-Trans-Asian and Pacific.
More than 80% of all earthquakes occur within the Pacific belt, including most of the catastrophic ones. A large number of earthquakes with subcrustal impact centers are concentrated here. About 15% of the total number of earthquakes is associated with the Mediterranean-Trans-Asian belt. Many earthquakes with intermediate focal depths occur here, and destructive earthquakes are also quite frequent.
Secondary zones and areas of seismicity are the Atlantic Ocean, the western Indian Ocean, and the Arctic regions. They account for less than 5% of all earthquakes.
The amount of seismic energy released in different active belts and zones is not the same. About 80% of the Earth's seismic energy is released in the Pacific belt and its branches, that is, where volcanic activity was and is most intense. More than 15% of the energy is released in the Mediterranean-Trans-Asian belt and less than 5% in other seismic zones and areas.
The eastern branch of the Pacific seismic belt, encircling the entire vast expanse of the Pacific Ocean, begins on the eastern coasts of Kamchatka, passes through the Aleutian Islands and the western coasts of North and South America and ends with the South Antilles loop, running from the southern tip of South America through the Folkleid Islands and the island of South Georgia . In the equatorial region, the Caribbean, or Antilles, loop branches off from the eastern branch of the Pacific seismic belt.
The most intense seismicity is in the northern part of the Pacific branch, where impacts with a force of up to 0.79 X 10 26 ergs occur, as well as the seismicity of its Californian branch. Within Central and South America, seismicity is somewhat less significant, although a large number of subcrustal impacts of varying depths have been recorded there.
The western branch of the Pacific belt stretches along Kamchatka and the Kuril Islands to Japan, where it, in turn, is divided into two branches - western and eastern. The western one goes through the Ryu-kyu Islands, Taiwan and the Philippines, and the eastern one goes through the Bonin Islands to the Mariana Islands. In the area of the Mariana Islands, subcrustal earthquakes with intermediate focal depths are very frequent.
The western branch from the Philippines heads to the Moluccas, goes around the Banda Sea and through the Sunda and Nicobar Islands stretches to the Andraman archipelago, apparently connecting through Burma with the Mediterranean-Trans-Asian belt.
The eastern branch from the island of Guam goes through the Pallau Islands to the western tip of New Guinea. There it turns sharply to the east and runs along the northern coast of New Guinea, the Solomon Islands, the New Hebrides and the Fiji Islands to the Tonga Archipelago, where it turns sharply south, stretching along the Tonga Trench, the Kermadec Trench and New Zealand. South of New Zealand it makes a sharp loop to the west and then goes east through Macquarie Island to the South Pacific Ocean. Information about the seismicity of the South Pacific Ocean is still insufficient, but it can be assumed that the South Pacific seismic zone is connected through Easter Island to the South American zone.
Within the western branch of the Pacific seismic belt, a significant number of subcrustal earthquakes have been recorded. A strip of deep sources runs under the bottom of the Sea of Okhotsk along the Kuril and Japanese Islands to Manchuria, then turns almost at a right angle to the southeast and, crossing the Sea of Japan and South Japan, goes to the Mariana Islands.
The second line of frequent subcrustal earthquakes occurs in the area of the Tonga and Kermadec deep-sea basins. A significant number of deep-focus strikes are also recorded within the Java Sea and the Banda Sea north of the Lesser Sunda Islands.
The Mediterranean-Trans-Asian seismic belt in the west includes the region of young subsidence ovals of the Mediterranean Sea. From the north it is limited by the southern tip of the Alps. The Alps themselves, as well as the Carpathians, are less seismic. The active zone covers the Apennines and Sicily and extends through the Balkans, the islands of the Aegean Sea, Crete and Cyprus into Asia Minor. The Romanian node of this zone is active, in which strong earthquakes with a focal depth of up to 150 km have repeatedly occurred. To the east, the active zone of the belt expands, covers Iran and Baluchistan and, in the form of a wide strip, stretches further east to Burma.
Strong impacts with focal depths of up to 300 km are often observed in the Hindu Kush.
The seismic zone of the Atlantic Ocean begins in the Greenland Sea, through the island of Jan Mayen and Iceland it goes south along the Mid-Atlantic underwater ridge and is lost at the Tristan da Cunha islands. This zone is most active in the equatorial part, but strong impacts are rare here.
The seismic zone of the western Indian Ocean stretches across the Arabian Peninsula and goes south and then southwest along the ocean floor along the seamount to Antarctica. Strong impacts seem to be rare here, but it should be borne in mind that this entire zone has not yet been sufficiently studied. An inland seismic zone runs along the eastern coast of Africa, confined to a strip of East African grabens.
Small earthquakes with shallow sources are observed within the Arctic zone. They occur quite often, but are not always recorded due to the weak intensity of the tremors and the great distance from seismic stations.
The outlines of the Earth's seismic belts are peculiar and mysterious (Fig. 21). They seem to border more stable blocks of the earth's crust - ancient platforms, but sometimes penetrate into them. Of course, seismic belts are associated with zones of giant crustal faults - ancient and younger. But why did these fault zones form where they are now? This question cannot yet be answered. The mystery is hidden in the depths of the planet.
The Earth's seismic belts (Greek seismos - earthquake) are boundary zones between lithospheric plates, which are characterized by high mobility and frequent earthquakes, and are also areas where most active volcanoes are concentrated. The length of seismic areas is thousands of kilometers. These areas correspond to deep faults on land, and in the ocean - mid-ocean ridges and deep-sea trenches.
Currently, two huge belts are distinguished: latitudinal Mediterranean-Trans-Asian and meridional Pacific. Belts of seismic activity correspond to areas of active mountain building and volcanism.
The Mediterranean-Trans-Asian belt includes the Mediterranean and the surrounding mountain ranges of Southern Europe, Asia Minor, North Africa, as well as most of the territory of Central Asia, the Caucasus, Kun-Lun, and the Himalayas. This belt accounts for about 15% of all earthquakes in the world, the depth of which is intermediate, but there can also be very destructive cataclysms.
80% of earthquakes occur in the Pacific Seismic Belt, which covers islands and deep-sea trenches in the Pacific Ocean. Along the periphery of the ocean in this belt there are seismically active zones of the Aleutian Islands, Alaska, the Kuril Islands, Kamchatka, the Philippine Islands, Japan, New Zealand, Hawaii, North and South America. Earthquakes with subcrustal shock sources often occur here, which have catastrophic consequences, in particular, provoking tsunamis.
The eastern branch of the Pacific Belt originates off the eastern coast of Kamchatka, covers the Aleutian Islands, runs along the western coast of North and South America and ends in the South Antilles Loop. The highest seismicity is observed in the northern part of the Pacific branch and in the California region of the USA. In the area of Central and South America, seismicity is less pronounced, but even in these areas, strong earthquakes may occasionally occur.
The western branch of the Pacific seismic belt stretches from the Philippines to the Moluccas, passes through the Banda Sea, the Nicobar and Sunda Islands to the Andraman archipelago. According to scientists, the western branch through Burma connects to the Trans-Asian belt. In the area of the western branch of the Pacific seismic belt, a large number of subcrustal earthquakes are observed. Deep foci are located under the bottom of the Sea of Okhotsk along the Japanese and Kuril Islands, then a strip of deep foci extends to the southeast, crossing the Sea of Japan to the Mariana Islands.
There are secondary zones of seismicity: the Atlantic Ocean, the western regions of the Indian Ocean, and the Arctic. About 5% of all earthquakes occur in these areas. The seismic region of the Atlantic Ocean originates in Greenland, runs south along the Mid-Atlantic submarine ridge and ends at the Tristan da Cunha islands. There are no strong impacts here. A strip of seismic zone in the western Indian Ocean passes through the Arabian Peninsula to the south, then southwest along the submarine rise to Antarctica. Here, as in the Arctic zone, mild earthquakes with shallow foci occur.
The Earth's seismic belts are located in such a way that they seem to border stable huge blocks of the earth's crust - platforms formed in ancient times. Sometimes they can enter their territory. It has been proven that the presence of seismic belts is closely related to faults in the earth’s crust, both ancient and more modern.
Ratios of areas and perimeters of geological bodies. Some definitions. Fractal dimension. Ratios of area (S) and perimeter (P) for terranes of different ages. Pyramid block structure. Distribution of earthquake epicenters. Ratio of area (S) and perimeter. Area-perimeter relationship. Data types. Size distributions. Fractal dimension of terranes. Fractal dimension of different types of terrains.
“Weathering” - 5. The work of the wind. Gullies are deep gullies tens of meters long and have steep slopes. 3. Natural diggers. Change in rock composition. Work through the corresponding paragraph of the textbook. USA. It is led by an experienced scientist - a chemist. Dunes 200-500m. Chemical weathering. Sometimes external forces lead to disruption of human economic activities. Organic weathering. Valley of Ghosts on Chatyr-Dag.
“Movement of lithospheric plates” - Llullaillaco Volcano. Provisions of the theory of lithospheric plates. Formation of the oceanic crust. Scientists. Interesting fact. Planetary compression belts. Divergence of lithospheric plates. The continental drift hypothesis and the theory of lithospheric plates. Lithospheric plates. Underwater ridge. Features of lithospheric plates. Earthquakes and volcanism. The structure of the earth's crust. Earth's crust. Changing the outlines of continents. Sections of the earth's crust.
“Structure of the lithosphere” - Zheleznyak. Helper tasks. Workshop. Lithosphere. Coal. Internal structure of the Earth. View of planet Earth from space and in section. The structure of the earth's crust. Limestone. Determining the mood. Excursion to the virtual geological museum. Solve the problem. Granite. Earth and its structure. Quartz. Tasks for consolidation. Hematite. An idea of the internal structure of the Earth.
“Tectonic structure and relief” - Earth’s Core. Intraplate processes. Collision of lithospheric plates. Structure of the Earth. Hawaiian Islands. Oceanic crust. Age of oceanic crust. Kola superdeep well. Age of the Earth. Plate boundaries. Lithosphere. Movable areas. Mid-ocean ridges. Thickness of the earth's crust in kilometers. Strike-slip movements along transform faults. Earth's mantle. Subduction of lithospheric plates. Discrepancy.
“Historical Geology” - The main tasks of geology. Scheme of global tectonics. The principle of incompleteness of the geological record. Historical geology. The principle of actualism. Superposition principle. Relative age of rocks. Diluvianism. Continents. Geological maps. Development of elementary observation techniques. Intersecting relationships. Modern geology. The principle of final succession. Spheres of the Earth. Xenoliths. Model of basic heat and mass transfer.
On Earth there are special zones of increased seismic activity, where earthquakes constantly occur. Why is this happening? Why do earthquakes occur more often in mountainous areas and very rarely in deserts? Why do earthquakes occur constantly in the Pacific Ocean, generating tsunamis of varying degrees of danger, but we have heard almost nothing about earthquakes in the Arctic Ocean. It's all about the seismic belts of the earth.
The earth's seismic belts are places where the planet's lithospheric plates come into contact with each other. In these zones, where the Earth's seismic belts are formed, there is increased mobility of the earth's crust, volcanic activity caused by the process of mountain building, which lasts for millennia.
The length of these belts is incredibly large - the belts stretch for thousands of kilometers.
There are two large seismic belts on the planet: the Mediterranean-Trans-Asian and the Pacific.
Mediterranean-Trans-Asian the belt originates off the coast of the Persian Gulf and ends in the mid-Atlantic Ocean. This belt is also called the latitudinal belt, since it runs parallel to the equator.
Pacific belt– meridional, it stretches perpendicular to the Mediterranean-Trans-Asian belt. It is along the line of this belt that a huge number of active volcanoes are located, most of whose eruptions occur under the water column of the Pacific Ocean itself.
If you draw the Earth's seismic belts on a contour map, you will get an interesting and mysterious picture. The belts seem to border the ancient platforms of the Earth, and sometimes penetrate into them. They are associated with giant faults in the earth's crust, both ancient and younger.
The Earth's latitudinal seismic belt passes through the Mediterranean Sea and all the adjacent European mountain ranges located in the south of the continent. It stretches through the mountains of Asia Minor and North Africa, reaches the mountain ranges of the Caucasus and Iran, and runs through all of Central Asia and the Hindu Kush straight to Koel Lun and the Himalayas.
In this belt, the most active seismic zones are the Carpathian Mountains, located in Romania, all of Iran and Baluchistan. From Baluchistan the earthquake zone stretches to Burma.
Fig.2. Mediterranean-Trans-Asian seismic belt
This belt has active seismic zones, which are located not only on land, but also in the waters of two oceans: the Atlantic and Indian. This belt also partially covers the Arctic Ocean. The seismic zone of the entire Atlantic passes through the Greenland Sea and Spain.
The most active seismic zone of the latitudinal belt is located on the bottom of the Indian Ocean, passes through the Arabian Peninsula and stretches to the very south and southwest of Antarctica.
But, no matter how dangerous the latitudinal seismic belt is, the majority of all earthquakes (about 80%) that occur on our planet occur in the Pacific belt of seismic activity. This belt runs along the bottom of the Pacific Ocean, along all the mountain ranges encircling this largest ocean on Earth, and captures the islands located in it, including Indonesia.
Fig.3. Pacific seismic belt.
The largest part of this belt is the Eastern one. It originates in Kamchatka, stretches through the Aleutian Islands and the western coastal zones of North and South America straight to the South Antilles loop.
The eastern branch is unpredictable and little studied. It is full of sharp and twisting turns.
The northern part of the belt is the most seismically active, which is constantly felt by residents of California, as well as Central and South America.
The western part of the meridional belt originates in Kamchatka, stretches to Japan and beyond.
It is no secret that during earthquakes, waves from vibrations of the earth's crust can reach remote areas that are generally considered safe with regard to seismic activity. In some places, the echoes of earthquakes are not felt at all, and in others they reach several points on the Richter scale.
Fig.4. Map of Earth's seismic activity.
Basically, these zones, sensitive to vibrations of the earth's crust, are located under the water column of the World Ocean. The planet's secondary seismic belts are located in the waters of the Atlantic, Pacific Ocean, Indian Ocean and the Arctic. Most of the secondary belts are located in the eastern part of the planet, so these belts stretch from the Philippines, gradually descending to Antarctica. The echoes of tremors can still be felt in the Pacific Ocean, but in the Atlantic there is almost always a seismically calm zone.
So, on Earth, earthquakes do not occur in random places. It is possible to predict the seismic activity of the earth's crust, since the bulk of earthquakes occur in special zones called seismic belts of the earth. There are only two of them on our planet: the Latitudinal Mediterranean-Trans-Asian seismic belt, which stretches parallel to the Equator, and the meridional Pacific seismic belt, located perpendicular to the latitudinal one.
The Earth's seismic belts (Greek seismos - earthquake) are boundary zones between lithospheric plates, which are characterized by high mobility and frequent earthquakes, and are also areas where most active volcanoes are concentrated. The length of seismic areas is thousands of kilometers. These areas correspond to deep faults on land, and in the ocean - mid-ocean ridges and deep-sea trenches.
Currently, two huge belts are distinguished: latitudinal Mediterranean-Trans-Asian and meridional Pacific. Belts of seismic activity correspond to areas of active mountain building and volcanism.
The Mediterranean-Trans-Asian belt includes the Mediterranean and the surrounding mountain ranges of Southern Europe, Asia Minor, North Africa, as well as most of the territory of Central Asia, the Caucasus, Kun-Lun, and the Himalayas. This belt accounts for about 15% of all earthquakes in the world, the depth of which is intermediate, but there can also be very destructive cataclysms.
80% of earthquakes occur in the Pacific Seismic Belt, which covers islands and deep-sea trenches in the Pacific Ocean. Along the periphery of the ocean in this belt there are seismically active zones of the Aleutian Islands, Alaska, the Kuril Islands, Kamchatka, the Philippine Islands, Japan, New Zealand, Hawaii, North and South America. Earthquakes with subcrustal shock sources often occur here, which have catastrophic consequences, in particular, provoking tsunamis.
The eastern branch of the Pacific Belt originates off the eastern coast of Kamchatka, covers the Aleutian Islands, runs along the western coast of North and South America and ends in the South Antilles Loop. The highest seismicity is observed in the northern part of the Pacific branch and in the California region of the USA. In the area of Central and South America, seismicity is less pronounced, but even in these areas, strong earthquakes may occasionally occur.
The western branch of the Pacific seismic belt stretches from the Philippines to the Moluccas, passes through the Banda Sea, the Nicobar and Sunda Islands to the Andraman archipelago. According to scientists, the western branch through Burma connects to the Trans-Asian belt. In the area of the western branch of the Pacific seismic belt, a large number of subcrustal earthquakes are observed. Deep foci are located under the bottom of the Sea of Okhotsk along the Japanese and Kuril Islands, then a strip of deep foci extends to the southeast, crossing the Sea of Japan to the Mariana Islands.
There are secondary zones of seismicity: the Atlantic Ocean, the western regions of the Indian Ocean, and the Arctic. About 5% of all earthquakes occur in these areas. The seismic region of the Atlantic Ocean originates in Greenland, runs south along the Mid-Atlantic submarine ridge and ends at the Tristan da Cunha islands. There are no strong impacts here. A strip of seismic zone in the western Indian Ocean passes through the Arabian Peninsula to the south, then southwest along the submarine rise to Antarctica. Here, as in the Arctic zone, mild earthquakes with shallow foci occur.
The Earth's seismic belts are located in such a way that they seem to border stable huge blocks of the earth's crust - platforms formed in ancient times. Sometimes they can enter their territory. It has been proven that the presence of seismic belts is closely related to faults in the earth’s crust, both ancient and more modern.
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The Earth's seismic belts are zones where the lithospheric plates that make up our planet come into contact with each other. The main characteristic of such areas is increased mobility, which can be expressed in frequent earthquakes, as well as in the presence of active volcanoes, which tend to erupt from time to time. Typically, such regions of the Earth stretch for thousands of miles in length. A large fault can be traced throughout this entire distance. If such a ridge is located on the ocean floor, it looks like a mid-oceanic trench.
According to generally accepted geographical theory, there are now two largest seismic belts on the planet. These include one latitudinal, that is, located along the equator, and the second is meridian, respectively, perpendicular to the previous one. The first is called the Mediterranean-Trans-Asian and it originates approximately in the Persian Gulf, and the extreme point reaches the middle of the Atlantic Ocean. The second is called the Pacific meridional, and it passes in full accordance with its name. It is in these areas that the greatest seismic activity is observed. Mountain formations have their place here, and also constantly. If these seismic belts of the Earth are viewed on a world map, it becomes clear that most eruptions occur precisely in the underwater part of our planet.
It is important to know that 80 percent of all earthquakes and volcanic eruptions occur in the Pacific Mountain Range. Most of it is located under salt waters, but it also affects some parts of the land. For example, precisely because of the splitting of the earth's rocks, earthquakes constantly occur, which often lead to a large number of human casualties. Further, this giant ridge includes smaller seismic belts of the Earth. So, it includes Kamchatka. It affects the western coast of the entire American continent and ends right on the South Antilles Loop. That is why all residential regions that are located along this line constantly experience more or less strong earth tremors. Among the most popular giant cities that are located in this unstable area is Los Angeles.
Now let's look at the zones of so-called secondary earthquakes, or secondary seismicity. All of them are quite densely located within our planet, but in some places the echoes are not audible at all, while in other regions the tremors reach almost a maximum. But it is worth noting that this situation is characteristic only of those lands that are under the waters of the World Ocean. The Earth's secondary seismic belts are concentrated in the waters of the Atlantic, in the Pacific Ocean, as well as in the Arctic and in some areas of the Indian Ocean. It is interesting that strong tremors, as a rule, occur precisely in the eastern part of all earthly waters, that is, the “Earth breathes” in the Philippines region, gradually descending lower to Antarctica. To some extent, the focus of these impacts also extends to the waters of the Pacific Ocean, but the Atlantic is almost always calm.
As mentioned above, the Earth's seismic belts are formed precisely at the junctions of the largest lithospheric plates. The largest of these is the meridian Pacific ridge, along the entire length of which there are a huge number of mountain elevations. As a rule, the source of shocks that causes tremors in this natural zone is subcrustal, so they spread over very long distances. The most seismically active branch of the meridian ridge is its northern part. Extremely high impacts are observed here, which often reach the California coast. It is for this reason that the number of skyscrapers that are built in a given area is always kept to a minimum. Please note that cities such as San Francisco and Los Angeles are, in general, one-story. High-rise buildings were built only in the city center. Heading lower, to the south, the seismicity of this branch decreases. On the west coast, the tremors are no longer as strong as in the North, but subcortical foci are still noted there.
The names of the Earth's seismic belts, which are branches of the main meridian Pacific Ridge, are directly related to their geographical location. One of the branches is Eastern. It originates off the coast of Kamchatka, runs along the Aleutian Islands, then goes around the entire American continent and ends at This zone is not catastrophically seismic, and the tremors that form within its boundaries are small. It is only worth noting that in the region of the equator a branch leaves from it to the East. The Caribbean Sea and all the island states that are located here are already in the Antilles seismic loop zone. This region previously experienced many earthquakes, which brought many disasters, but these days the Earth has “calmed down”, and the tremors, which are heard and felt in all resorts of the Caribbean, do not pose any danger to life.
If we look at the Earth’s seismic belts on a map, it turns out that the eastern branch of the Pacific Ridge runs along the westernmost land coast of our planet, that is, along America. The western branch of the same seismic belt begins at the Kuril Islands, passes through Japan, and then divides into two others. It is strange that the names of these seismic zones were chosen exactly the opposite. By the way, the two branches into which this strip is divided also have the names “Western” and “Eastern,” but this time their geographical affiliation coincides with generally accepted rules. The eastern one goes through New Guinea to New Zealand. Quite strong tremors can be traced in this area, often of a destructive nature. The eastern branch covers the shores of the Philippine Islands, the southern islands of Thailand, as well as Burma, and finally connects with the Mediterranean-Trans-Asian belt.
Now let's look at the lithospheric region that is located closer to our region. As you already understand, the name of the seismic belts of our planet depends on their location, and in this case, the Mediterranean-Trans-Asian ridge is proof of this. Within its extent are the Alps, Carpathians, Apennines and islands located in the Mediterranean Sea. The greatest seismic activity occurs in the Romanian node, where strong tremors are observed quite often. Moving to the East, this belt covers the lands of Balochistan, Iran and ends in Burma. However, the total percentage of seismic activity that occurs in this area is only 15. Therefore, this region is quite safe and calm.
There are special zones of increased seismic activity on Earth, where earthquakes constantly occur. Why is this happening? Why do earthquakes occur more often in mountainous areas and very rarely in deserts? Why do earthquakes occur constantly in the Pacific Ocean, generating tsunamis of varying degrees of danger, but we have heard almost nothing about earthquakes in the Arctic Ocean. It's all about the seismic belts of the earth.
The earth's seismic belts are places where the planet's lithospheric plates come into contact with each other. In these zones, where the Earth's seismic belts are formed, there is increased mobility of the earth's crust and volcanic activity caused by the process of mountain building, which lasts for millennia.
The length of these belts is incredibly large - the belts stretch for thousands of kilometers.
There are two large seismic belts on the planet: the Mediterranean-Trans-Asian and the Pacific.
Rice. 1. Seismic belts of the Earth.
Mediterranean-Trans-Asian The belt originates off the coast of the Persian Gulf and ends in the middle of the Atlantic Ocean. This belt is also called the latitudinal belt, since it runs parallel to the equator.
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Pacific belt– meridional, it stretches perpendicular to the Mediterranean-Trans-Asian belt. It is along the line of this belt that a huge number of active volcanoes are located, most of whose eruptions occur under the water column of the Pacific Ocean itself.
If you draw the Earth's seismic belts on a contour map, you will get an interesting and mysterious picture. The belts seem to border the ancient platforms of the Earth, and sometimes penetrate into them. They are associated with giant faults in the earth's crust, both ancient and younger.
The Earth's latitudinal seismic belt passes through the Mediterranean Sea and all the adjacent European mountain ranges located in the south of the continent. It stretches through the mountains of Asia Minor and North Africa, reaches the mountain ranges of the Caucasus and Iran, and runs through all of Central Asia and the Hindu Kush straight to Koel Lun and the Himalayas.
In this belt, the most active seismic zones are the Carpathian Mountains, located in Romania, all of Iran and Baluchistan. From Baluchistan the earthquake zone stretches to Burma.
Fig.2. Mediterranean-Trans-Asian seismic belt
This belt has active seismic zones, which are located not only on land, but also in the waters of two oceans: the Atlantic and Indian. This belt also partially covers the Arctic Ocean. The seismic zone of the entire Atlantic passes through the Greenland Sea and Spain.
The most active seismic zone of the latitudinal belt occurs at the bottom of the Indian Ocean, passes through the Arabian Peninsula and stretches to the very south and southwest of Antarctica.
But, no matter how dangerous the latitudinal seismic belt is, the majority of all earthquakes (about 80%) that occur on our planet occur in the Pacific belt of seismic activity. This belt runs along the bottom of the Pacific Ocean, along all the mountain ranges encircling this largest ocean on Earth, and captures the islands located in it, including Indonesia.
Fig.3. Pacific seismic belt.
The largest part of this belt is the Eastern one. It originates in Kamchatka, stretches through the Aleutian Islands and the western coastal zones of North and South America straight to the South Antilles loop.
The eastern branch is unpredictable and little studied. It is full of sharp and twisting turns.
The northern part of the belt is the most seismically active, which is constantly felt by residents of California, as well as Central and South America.
The western part of the meridional belt originates in Kamchatka, stretches to Japan and beyond.
It is no secret that during earthquakes, waves from vibrations of the earth's crust can reach remote areas that are generally considered safe with regard to seismic activity. In some places, the echoes of earthquakes are not felt at all, and in others they reach several points on the Richter scale.
Fig.4. Map of Earth's seismic activity.
Basically, these zones, sensitive to vibrations of the earth's crust, are located under the water column of the World Ocean. The planet's secondary seismic belts are located in the waters of the Atlantic, Pacific Ocean, Indian Ocean and the Arctic. Most of the secondary belts are located in the eastern part of the planet, so these belts stretch from the Philippines, gradually descending to Antarctica. The echoes of tremors can still be felt in the Pacific Ocean, but in the Atlantic there is almost always a seismically calm zone.
So, on Earth, earthquakes do not occur in random places. It is possible to predict the seismic activity of the earth's crust, since the bulk of earthquakes occur in special zones called seismic belts of the earth. There are only two of them on our planet: the Latitudinal Mediterranean-Trans-Asian seismic belt, which stretches parallel to the Equator, and the meridional Pacific seismic belt, located perpendicular to the latitudinal one.
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