What cities experience earthquakes? San Francisco. Seismically active regions of Russia

Hundreds of thousands of earthquakes occur every year on our planet. Most of them are so small and insignificant that only special sensors can detect them. But, there are also more serious fluctuations: twice a month the earth's crust shudders strongly enough to destroy everything around.

Since most shocks of this magnitude occur at the bottom of the oceans, if they are not accompanied by a tsunami, people are not even aware of them. But when the land shudders, the elements are so destructive that the number of victims goes into the thousands, as happened in the 16th century in China (during earthquakes with a magnitude of 8.1, more than 830 thousand people died).

Earthquake refers to tremors and vibrations earth's crust caused by natural or artificially created causes (movement of lithospheric plates, volcanic eruptions, explosions). Aftershocks great intensity are often catastrophic, second only to typhoons in the number of victims.

Unfortunately, on this moment scientists have not studied the processes that take place in the bowels of our planet so well, and therefore the earthquake forecast is rather approximate and inaccurate. Among the causes of earthquakes, experts identify tectonic, volcanic, landslide, artificial and man-made fluctuations of the earth's crust.

Tectonic

Most of the earthquakes recorded in the world arose as a result of movements of tectonic plates, when there is a sharp displacement of rocks. This can be either a collision with each other, or lowering a thinner plate under another.

Although this shift is usually small, and is only a few centimeters, the mountains located above the epicenter begin to move, which release tremendous energy. As a result, on earth's surface cracks form, along the edges of which huge tracts of land begin to shift along with everything that is on it - fields, houses, people.

Volcanic

But volcanic fluctuations, although weak, continue for a long time. Usually they do not pose a particular danger, but catastrophic consequences were still recorded. As a result of the most powerful eruption of the Krakatoa volcano at the end of the XIX century. half of the mountain was destroyed by the explosion, and the subsequent tremors were of such force that they split the island into three parts, plunging two thirds into the abyss. The tsunami that rose after that destroyed absolutely everyone who managed to survive before and did not have time to leave the dangerous territory.

landslide

It is impossible not to mention collapses and large landslides. Usually these concussions are not strong, but in some cases their consequences are catastrophic. So, it happened once in Peru, when a huge avalanche, causing an earthquake, descended from Mount Askaran at a speed of 400 km / h, and, having leveled more than one settlement, killed more than eighteen thousand people.

man-made

In some cases, the causes and consequences of earthquakes are often associated with human activity. Scientists have recorded an increase in the number of tremors in areas of large reservoirs. This is due to the fact that the collected mass of water begins to put pressure on the underlying earth's crust, and the water penetrating through the soil destroys it. In addition, an increase in seismic activity has been observed in oil and gas production areas, as well as in the area of ​​mines and quarries.

artificial

Earthquakes can also be caused artificially. For example, after the DPRK tested a new nuclear weapon, in many places on the planet, sensors recorded earthquakes of moderate strength.

An underwater earthquake occurs when tectonic plates collide on the ocean floor or near the coast. If the focus is shallow, and the magnitude is 7 points, an underwater earthquake is extremely dangerous because it causes a tsunami. During the shudder of the sea crust, one part of the bottom sinks, the other rises, as a result of which the water, in an attempt to return to its original position, begins to move vertically, generating a series of huge waves going towards the coast.

Such an earthquake, together with a tsunami, can often have catastrophic consequences. For example, one of the strongest seaquakes occurred several years ago in Indian Ocean: as a result of underwater tremors rose big tsunami and, having fallen on the nearby coasts, led to the death of more than two hundred thousand people.

Start of shocks

The focus of an earthquake is a gap, after the formation of which the earth's surface instantly shifts. It should be noted that this gap does not occur immediately. First, the plates collide with each other, as a result of which friction occurs and energy is generated, which gradually begins to accumulate.

When the stress reaches its maximum and begins to exceed the force of friction, the rocks are torn apart, after which the released energy is converted into seismic waves moving at a speed of 8 km / s and causing the earth to vibrate.

The characteristics of earthquakes according to the depth of the epicenter are divided into three groups:

1. Normal - epicenter up to 70 km;
2. Intermediate - epicenter up to 300 km;
3. Deep focus - the epicenter at a depth exceeding 300 km, typical for the Pacific Rim. The deeper the epicenter, the farther the seismic waves generated by the energy will reach.

Characteristic

An earthquake consists of several stages. The main, most powerful shock is preceded by warning oscillations (foreshocks), and after it, aftershocks begin, subsequent shaking, and the magnitude of the strongest aftershock is 1.2 less than that of the main shock.

The period from the beginning of foreshocks to the end of aftershocks may well last several years, as, for example, happened at the end of the 19th century on the island of Lissa in the Adriatic Sea: it lasted three years and during this time scientists recorded 86,000 shocks.

As for the duration of the main shock, it is usually short and rarely lasts more than a minute. For example, the most powerful shock in Haiti, which occurred a few years ago, lasted forty seconds - and that was enough to reduce the city of Port-au-Prince to ruins. But in Alaska, a series of aftershocks was recorded that shook the earth for about seven minutes, while three of them led to significant destruction.

It is extremely difficult, problematic and there are no 100% ways to calculate what kind of push will be the main one and will have the greatest magnitude. Therefore, strong earthquakes often take the population by surprise. So, for example, it happened in 2015 in Nepal, in a country where mild shaking was recorded so often that people simply did not pay attention to them. special attention. Therefore, a 7.9-magnitude ground tremor resulted in a large number of casualties, and weaker aftershocks of magnitude 6.6 that followed half an hour later and the next day did not improve the situation.

It often happens that the strongest tremors occurring on one side of the planet shake the opposite side. For example, a 2004 magnitude 9.3 earthquake in the Indian Ocean eased some of the rising stress on the San Andreas Fault, which lies at the junction of lithospheric plates along the coast of California. It turned out to be of such strength that it slightly changed the appearance of our planet, smoothing out its bulge in the middle part and making it more rounded.

What is magnitude

One of the ways to measure the amplitude of oscillations and the amount of energy released is the magnitude scale (Richter scale), containing arbitrary units from 1 to 9.5 (it is often confused with the twelve-point intensity scale, measured in points). An increase in the magnitude of earthquakes by only one unit means an increase in the amplitude of oscillations by a factor of ten, and an increase in energy by a factor of thirty-two.

The calculations performed showed that the size of the epicenter during weak surface oscillations, both in length and vertically, is measured in several meters, when of average strength - in kilometers. But earthquakes that cause catastrophes have a length of up to 1 thousand kilometers and go from the break point to a depth of up to fifty kilometers. Thus, the maximum recorded size of the epicenter of earthquakes on our planet was 1000 per 100 km.

The magnitude of earthquakes (Richter scale) looks like this:

• 2 - weak almost imperceptible fluctuations;
• 4 - 5 - although the shocks are weak, they can lead to minor damage;
• 6 - medium destruction;
• 8.5 is one of the strongest recorded earthquakes.
• The largest is the Great Chilean earthquake with a magnitude of 9.5, which gave rise to a tsunami, which, having overcome the Pacific Ocean, reached Japan, having overcome 17 thousand kilometers.

Focusing on the magnitude of earthquakes, scientists argue that out of tens of thousands of oscillations occurring on our planet per year, only one has a magnitude of 8, ten - from 7 to 7.9 and one hundred - from 6 to 6.9. Keep in mind that if the magnitude of the earthquake is 7, the consequences can be catastrophic.

intensity scale

To understand why earthquakes occur, scientists have developed a scale of intensity based on such external manifestations as the impact on people, animals, buildings, nature. The closer the epicenter of earthquakes to the earth's surface, the greater the intensity (this knowledge makes it possible to give at least an approximate forecast of earthquakes).

For example, if the magnitude of the earthquake was eight, and the epicenter was at a depth of ten kilometers, the intensity of the earthquake will be from eleven to twelve points. But if the epicenter was located at a depth of fifty kilometers, the intensity will be less and will be measured at 9-10 points.

According to the scale of intensity, the first destruction can occur already with six-point shocks, when thin cracks appear in the plaster. An earthquake of eleven points is considered catastrophic (the surface of the earth's crust is covered with cracks, buildings are destroyed). The strongest earthquakes that can significantly change the appearance of the area are estimated at twelve points.

What to do in case of earthquakes

According to rough estimates of scientists, the number of people who have died in the world due to earthquakes over the past half a millennium exceeds five million people. Half of them are in China: it is located in a zone of seismic activity, and a large number of people live on its territory (830 thousand people died in the 16th century, 240 thousand in the middle of the last century).

Such catastrophic consequences could have been prevented if earthquake protection had been well thought out in state level, and when designing buildings, the possibility of strong tremors was taken into account: most people died under the rubble. Often people living or staying in a seismically active zone have no idea how exactly to act in an emergency and how you can save your life.

You need to know that if tremors caught you in a building, you need to do everything possible to get out into the open space as soon as possible, while using elevators is absolutely impossible.

If it is impossible to leave the building, and the earthquake has already begun, it is extremely dangerous to leave it, so you need to stand either in the doorway, or in the corner near the load-bearing wall, or climb under a strong table, protecting your head with a soft pillow from objects that may fall from above. After the tremors are over, the building must be left.

If during the beginning of earthquakes a person was on the street, you need to move away from the house at least one third of its height and, avoiding tall buildings, fences and other buildings, move in the direction of wide streets or parks. It is also necessary to stay as far away from broken electrical wires as possible. industrial enterprises because explosive materials or poisonous substances may be stored there.

But if the first tremors caught a person when he was in a car or public transport need to get out of the vehicle immediately. If the car is in an open area, on the contrary, stop the car and wait out the earthquake.

If it so happened that you were completely overwhelmed with debris, the main thing is not to panic: a person can survive without food and water for several days and wait until they find him. After catastrophic earthquakes, rescuers work with specially trained dogs, and they are able to smell life among the rubble and give a sign.

The content of the article

EARTHQUAKE, Earth wobbles caused by sudden changes in the state of the planet's interior. These vibrations are elastic waves propagating at high speed in the rock mass. The strongest earthquakes are sometimes felt at distances of more than 1500 km from the source and can be recorded by seismographs (special highly sensitive instruments) even in the opposite hemisphere. The area where oscillations originate is called the source of the earthquake, and its projection on the Earth's surface is called the epicenter of the earthquake. The sources of most earthquakes lie in the earth's crust at depths of no more than 16 km, but in some regions the depths of the sources reach 700 km. There are thousands of earthquakes every day, but only a few of them are felt by humans.

Earthquakes are mentioned in the Bible, in the treatises of ancient scientists - Herodotus, Pliny and Livy, as well as in ancient Chinese and Japanese written sources. Until the 19th century most reports of earthquakes contained descriptions richly flavored with superstition and theories based on scanty and unreliable observations. A series of systematic descriptions (catalogues) of earthquakes was started in 1840 by A. Perry (France). In the 1850s, R.Malle (Ireland) compiled big catalog earthquakes, and his detailed account of the earthquake in Naples in 1857 was one of the first strictly scientific descriptions strong earthquakes.

Causes of earthquakes.

Although numerous studies have been carried out since ancient times, it cannot be said that the causes of earthquakes are fully understood. According to the nature of the processes in their sources, several types of earthquakes are distinguished, the main of which are tectonic, volcanic and man-made.

Tectonic earthquakes

arise as a result of a sudden release of stress, for example, when moving along a fault in the earth's crust (research recent years show that deep earthquakes can also be caused by phase transitions in the Earth's mantle that occur at certain temperatures and pressures). Sometimes deep faults come to the surface. During the catastrophic earthquake in San Francisco on April 18, 1906, the total length of surface ruptures in the San Andreas fault zone was more than 430 km, the maximum horizontal displacement was 6 m. The maximum recorded value of seismogenic displacements along the fault was 15 m.

Volcanic earthquakes

occur as a result of abrupt movements of the magmatic melt in the bowels of the Earth or as a result of the occurrence of ruptures under the influence of these movements.

Man-made earthquakes

may be caused by underground nuclear testing, filling reservoirs, extracting oil and gas by injecting liquid into wells, blasting during mining, etc. Less strong earthquakes occur when the arches of caves or mine workings collapse.

seismic waves.

Oscillations propagating from the source of an earthquake are elastic waves, the nature and speed of propagation of which depend on the elastic properties and density of rocks. The elastic properties include the modulus of volumetric deformation, which characterizes the resistance to compression without changing shape, and the shear modulus, which determines the resistance to shear forces. The propagation velocity of elastic waves increases in direct proportion to square root values ​​of elasticity and density parameters of the medium.

Longitudinal and transverse waves.

On seismograms, these waves appear first. First of all, longitudinal waves are recorded, during the passage of which each particle of the medium is first subjected to compression, and then expands again, while experiencing reciprocating motion in the longitudinal direction (i.e., in the direction of wave propagation). These waves are also called R- waves, or primary waves. Their speed depends on the modulus of elasticity and rock stiffness. Near the earth's surface speed R-waves is 6 km / s, and at very great depth- OK. 13 km/s. The next recorded are transverse seismic waves, also called S waves, or secondary waves. During their passage, each particle of the rock oscillates perpendicular to the direction of wave propagation. Their speed depends on the resistance of the rock to shear and is approximately 7/12 of the propagation speed. R- waves.

surface waves

propagate along the earth's surface or parallel to it and do not penetrate deeper than 80-160 km. Rayleigh waves and Love waves (named after the scientists who developed the mathematical theory of the propagation of such waves) stand out in this group. During the passage of Rayleigh waves, the rock particles describe vertical ellipses lying in the source plane. In Love waves, rock particles oscillate perpendicular to the direction of wave propagation. Surface waves are often abbreviated as L-waves. The speed of their propagation is 3.2-4.4 km/s. During deep-focus earthquakes, surface waves are very weak.

Amplitude and period

characterize oscillatory movements seismic waves. The amplitude is the amount by which the position of the soil particle changes during the passage of the wave compared to the previous state of rest. The period of oscillation is the period of time during which one complete oscillation of the particle takes place. Near the source of the earthquake, oscillations with different periods are observed - from fractions of a second to several seconds. However, at large distances from the center (hundreds of kilometers), short-period fluctuations are less pronounced: for R-waves are characterized by periods from 1 to 10 s, and for S- waves - a little more. The periods of surface waves range from a few seconds to several hundred seconds. Oscillation amplitudes can be significant near the source, but at distances of 1500 km or more they are very small - less than a few microns for waves R And S and less than 1 cm for surface waves.

Reflection and refraction.

Encountering on its way layers of rocks with different properties, seismic waves are reflected or refracted in the same way as a beam of light is reflected from a mirror surface or refracted, passing from air into water. Any changes in the elastic characteristics or density of the material along the propagation path of seismic waves cause them to be refracted, and with sharp changes in the properties of the medium, part of the wave energy is reflected ( cm. rice.).

Seismic wave paths.

Longitudinal and transverse waves propagate in the thickness of the Earth, while the volume of the medium involved in the oscillatory process continuously increases. The surface corresponding to the maximum advance of waves of a certain type at a given moment is called the front of these waves. Since the modulus of elasticity of the medium increases with depth faster than its density (up to a depth of 2900 km), the velocity of wave propagation at depth is higher than near the surface, and the wave front is more advanced in depth than in the lateral (lateral) direction. The trajectory of a wave is a line connecting a point located at the front of the wave with the source of the wave. Directions of wave propagation R And S are curves convex downward (due to the fact that the wave speed is greater at depth). Wave trajectories R And S coincide, although the former propagate faster.

Seismic stations located far from the epicenter of an earthquake register not only direct waves R And S, but also waves of these types, already reflected once from the surface of the Earth - RR And SS(or PR 1 And SR 1), and sometimes - reflected twice - RRR And SSS(or PR 2 and SR 2). There are also reflected waves that travel one segment of the path as R-wave, and the second, after reflection, - as S-wave. The resulting converted waves are denoted as PS or SP. On seismograms of deep-focus earthquakes, other types of reflected waves are also observed, for example, waves that are reflected from the Earth's surface before reaching the recording station. They are usually denoted by a small letter followed by a capital letter (for example, pR). These waves are very convenient to use to determine the depth of the earthquake source.

At a depth of 2900 km, the speed P-waves sharply decreases from >13 km/s to ~ 8 km/s; A S- waves do not propagate below this level, corresponding to the boundary of the earth's core and mantle . Both types of waves are partially reflected from this surface, and some of their energy returns to the surface in the form of waves, denoted as R with R And S with S. R-waves pass through the core, but their trajectory deviates sharply and a shadow zone appears on the Earth's surface, within which only very weak R-waves. This zone starts at a distance of approx. 11 thousand km from the seismic source, and already at a distance of 16 thousand km R-waves reappear, and their amplitude increases significantly due to the focusing effect of the nucleus, where the wave velocities are low. R-waves that have passed through the earth's core are denoted RKR or Rў . On seismograms, waves are also clearly distinguished, which, on the way from the source to the core, go like waves S, then pass through the core as waves R, and at the exit, the waves are again converted to the type S. In the very center of the Earth, at a depth of more than 5100 km, there is an inner core, which is presumably in a solid state, but its nature is not yet completely clear. Waves penetrating this inner core are denoted as RKICR or SKIKS(cm. rice. 1).

Earthquake registration.

A device that records seismic vibrations is called a seismograph, and the recording itself is called a seismogram. The seismograph consists of a pendulum suspended inside the case on a spring and a recording device.

One of the first recording devices was a rotating drum with paper tape. As the drum rotates, it gradually shifts to one side, so that the zero line of the record on the paper looks like a spiral. Every minute, vertical lines are drawn on the chart - time marks; for this, very accurate clocks are used, which are periodically compared with the standard of exact time. To study nearby earthquakes, marking accuracy is required - up to a second or less.

In many seismographs, to convert a mechanical signal into an electrical one, induction devices are used, in which, when the inertial mass of the pendulum moves relative to the body, the magnitude of the magnetic flux passing through the turns of the induction coil changes. The resulting weak electricity actuates a galvanometer connected to a mirror, which casts a beam of light onto the photosensitive paper of the recording device. In modern seismographs, oscillations are recorded digitally using computers.

Earthquake magnitude

usually determined on a scale based on seismograph records. This scale is known as the magnitude scale, or the Richter scale (after the American seismologist Ch.F. Richter, who proposed it in 1935). The magnitude of an earthquake is a dimensionless value proportional to the logarithm of the ratio of the maximum amplitudes of a certain type of waves of a given earthquake and some standard earthquake. There are differences in the methods for determining the magnitudes of near, distant, shallow (shallow) and deep earthquakes. Magnitudes determined by different types waves vary in size. Earthquakes of different magnitudes (on the Richter scale) manifest themselves as follows:

2 - the weakest felt shocks;

4 1 / 2 - the weakest shocks, leading to little damage;

6 - moderate destruction;

8 1/2 are the strongest known earthquakes.

Earthquake intensity

is estimated in points when examining the area according to the magnitude of the destruction of ground structures or deformations of the earth's surface caused by them. For a retrospective assessment of the intensity of historical or more ancient earthquakes, some empirically obtained ratios are used. In the US, intensity is usually assessed using a modified 12-point Mercalli scale.

1 point. It is felt by a few especially sensitive people in especially favorable circumstances.

3 points. It is felt by people like a vibration from a passing truck.

4 points. Dishes and glassware rattle, doors and walls creak.

5 points. Felt by almost everyone; many sleepers wake up. Loose objects fall.

6 points. Felt by everyone. Minor damage.

8 points. Chimneys fall, monuments fall, walls collapse. The water level in the wells is changing. Capital buildings are severely damaged.

10 points. Brick buildings and frame structures are destroyed. Rails are deformed, landslides occur.

12 points. Complete destruction. Waves are visible on the earth's surface.

In Russia and some neighboring countries, it is customary to evaluate the intensity of fluctuations in MSK points (12-point Medvedev-Sponheuer-Karnik scale), in Japan - in JMA points (9-point scale of the Japan Meteorological Agency).

The intensity in points (expressed as integers without fractions) is determined by surveying the area in which an earthquake occurred, or by asking residents about their feelings in the absence of destruction, or by calculations using empirically obtained and accepted formulas for this area. Among the first information about the earthquake that occurred, it is its magnitude, and not the intensity, that becomes known. The magnitude is determined from seismograms even at large distances from the epicenter.

The consequences of earthquakes.

Strong earthquakes leave many traces, especially in the epicenter area: the most common are landslides and screes of loose soil and cracks on the earth's surface. The nature of such disturbances is largely determined by the geological structure of the area. In loose and water-saturated soil on steep slopes, landslides and landslides often occur, and a thick layer of water-saturated alluvium in valleys deforms more easily than hard rocks. On the surface of alluvium, subsidence depressions are formed, which are filled with water. And even not very strong earthquakes are reflected in the terrain.

Displacements along faults or the occurrence of surface ruptures can change the plan and height position of individual points on the earth's surface along the fault line, as happened during the 1906 earthquake in San Francisco. During an earthquake in October 1915 in the Pleasant Valley in Nevada, a ledge 35 km long and up to 4.5 m high was formed on the fault. .5 m. As a result of the Assam earthquake (India) in June 1897 in the epicentral region, the height of the terrain changed by at least 3 m.

Significant surface deformations can be traced not only near faults and lead to a change in the direction of river flow, springing or rupture of watercourses, disruption of the regime of water sources, and some of them temporarily or permanently cease to function, but at the same time new ones may appear. Wells and wells swim with mud, and the water level in them changes significantly. During strong earthquakes, water, liquid mud or sand can be ejected from the ground in fountains.

When displaced along the faults, damage to automobile and railways, buildings, bridges and other engineering structures. However, well-constructed buildings rarely collapse completely. Usually the degree of destruction is directly dependent on the type of structure and the geological structure of the area. During earthquakes of moderate strength, partial damage to buildings can occur, and if they are poorly designed or poorly built, then their complete destruction is also possible.

With very strong tremors, structures built without taking seismic hazard into account can collapse and suffer severe damage. Usually one- and two-story buildings do not collapse, unless they have very heavy roofs. However, it happens that they are displaced from the foundations and often their plaster cracks and falls off.

Differentiated movements can lead to the fact that bridges move from their supports, and utilities and water pipes are torn. With intense vibrations, pipes laid in the ground can “fold”, sticking into one another, or bend, coming to the surface, and deform railway rails. In seismically hazardous areas, structures should be designed and built in compliance with the building codes adopted for the given area in accordance with the seismic zoning map.

In densely populated areas, almost more damage than the earthquakes themselves are caused by fires resulting from the rupture of gas pipelines and power lines, overturning stoves, stoves and various heating appliances. Fighting fires is difficult due to the fact that the water supply is damaged, and the streets are impassable due to blockages.

related phenomena.

Sometimes tremors are accompanied by a clearly distinguishable low rumble, when the frequency of seismic vibrations lies in the range perceived by the human ear, sometimes such sounds are heard even in the absence of tremors. They are fairly common in some areas, although tangible earthquakes are very rare. There are also numerous reports of the appearance of a glow during strong earthquakes. There is no generally accepted explanation for such phenomena. Tsunamis (large sea waves) are caused by rapid vertical deformations of the sea floor during underwater earthquakes. Tsunamis propagate in the oceans within deep water zones oceans at a speed of 400–800 km/h and can cause destruction on coasts thousands of kilometers away from the epicenter. Near the shores close to the epicenter, these waves sometimes reach a height of 30 m.

In many strong earthquakes, in addition to the main shocks, foreshocks (preceding earthquakes) and numerous aftershocks (earthquakes following the main shock) are recorded. Aftershocks are usually weaker than the main shock and may recur over weeks or even years, becoming less and less frequent.

Geographic distribution of earthquakes.

Most earthquakes are concentrated in two extended, narrow zones. One of them frames the Pacific Ocean, and the second stretches from the Azores to the east to South-East Asia.

The Pacific seismic zone runs along the western coast of South America. IN Central America it divides into two branches, one of which follows the island arc of the West Indies, and the other continues north, expanding within the United States, to the western ridges of the Rocky Mountains. Further, this zone passes through the Aleutian Islands to Kamchatka and then through the Japanese Islands, the Philippines, New Guinea and southwestern islands Pacific Ocean to New Zealand and Antarctica.

The second zone from the Azores extends east through the Alps and Turkey. In the south of Asia, it expands, and then narrows and changes direction to meridional, follows through the territory of Myanmar, the islands of Sumatra and Java and connects with the circum-Pacific zone in the area of ​​New Guinea.

There is also a smaller zone in the central part of the Atlantic Ocean, following along the Mid-Atlantic Ridge.

There are a number of areas where earthquakes occur quite often. These include East Africa, the Indian Ocean and North America valley of the St. Lawrence and northeastern United States.

Compared to shallow-focus earthquakes, deep-focus earthquakes have a more limited distribution. They have not been recorded within the Pacific zone from southern Mexico to the Aleutian Islands, and in the Mediterranean zone - to the west of the Carpathians. Deep-focus earthquakes are typical for western outskirts Pacific Ocean, Southeast Asia and the western coast of South America. The zone with deep-focus sources is usually located along the zone of shallow-focus earthquakes from the side of the mainland.

Earthquake forecast.

To improve the accuracy of earthquake prediction, it is necessary to better understand the mechanisms of stress accumulation in the Earth's crust, creep and deformations on faults, to identify the relationship between the heat flow from the Earth's interior and the spatial distribution of earthquakes, and also to establish patterns of earthquake recurrence depending on their magnitude.

In many areas of the globe where there is a possibility of strong earthquakes, geodynamic observations are carried out in order to detect earthquake precursors, among which changes in seismic activity, deformation of the earth's crust, anomalies in geomagnetic fields and heat flow deserve special attention, drastic changes properties of rocks (electrical, seismic, etc.), geochemical anomalies, disturbances water regime, atmospheric phenomena, as well as abnormal behavior of insects and other animals (biological precursors). Such studies are carried out at special geodynamic testing grounds (for example, Parkfield in California, Garm in Tajikistan, etc.). Since 1960, many seismic stations have been operating, equipped with highly sensitive recording equipment and powerful computers, allowing to quickly process data and determine the position of earthquake sources.

Most of the largest earthquakes follow the same scenario: rigid plate structures, consisting of the earth's crust and mantle, move by colliding with each other. In total, there are 7 largest plates in the world: Antarctic, Eurasian, Indo-Australian, North American, Pacific and South American.

Over the past two billion years, the movement of the plates has accelerated significantly, which, accordingly, increased the chances of such a catastrophe. On the other hand, based on studies of the movement of tectonic plates, scientists can, albeit approximately, predict the appearance of the next major earthquake. Based on publicly available data, we have estimated a list of cities where the likelihood of such an event is very high right now.

San Francisco

A powerful earthquake with an epicenter in the Santa Cruz Mountains, about a hundred kilometers from the city of San Francisco, is just around the corner. More specifically, over the next couple of years. However, most of the inhabitants of the City by the Bay prepared for the disaster by stocking up on medicines for the future, drinking water and food products. In turn, the city authorities are busy with the fact that they urgently carry out work to strengthen buildings.

Fremantle

Fremantle is a port city located on the west coast of Australia. According to seismological research by specialists from the University of Sydney, from the end of 2016 to 2024, a strong earthquake of about 6 on the Richter scale is expected there. However, the main danger is that the shock could occur at the bottom of the ocean near the city, causing a tsunami.

Tokyo

According to experts, a major earthquake with an epicenter in the Japanese capital with a probability of 75% can occur at any time within the next 30 years. According to the model created by scientists, about 23 thousand people will become a victim of the disaster and over 600 thousand buildings will be destroyed. In addition to improving the seismic resistance of buildings and demolishing old structures, the Tokyo administration will introduce non-combustible building materials. The 1995 Kobe earthquake showed the Japanese that people are more likely to fall victim not to collapsed buildings, but to post-disaster fires.

Los Angeles

Earthquakes in the City of Angels happen quite often, but there have been no truly large ones for more than a century. The more gloomy is the forecast presented by seismologists and geologists from the US Geological Society. Based on the analysis of soils and tectonic plates under central part California, scientists concluded that before 2037 an earthquake of magnitude 6.7 could occur here. A push of such force, under certain circumstances, can turn a city into ruins.

Panama

Within a few next years a powerful earthquake, with a power of more than 8.5 on the Richter scale, will occur in the Isthmus of Panama region. These conclusions were made by specialists from the University of San Diego, after they conducted seismological studies of faults adjacent to the Panama Canal. The action of an earthquake of truly catastrophic proportions will be felt by the inhabitants of both Americas. And most of all, of course, the capital of the republic, Panama, where about 1.5 million people live, will suffer.

Petropavlovsk-Kamchatsky

A strong earthquake in the medium term, that is, in the next 4-5 years, will occur in the area of ​​Petropavlovsk-Kamchatsky. Such data were reported in the seismology department of the Schmidt Institute of Physics of the Earth. In connection with this forecast, work is underway to strengthen buildings in Kamchatka, and the Ministry of Emergency Situations checks the seismic resistance of buildings. In addition, a network of stations was organized to monitor the symptoms of an approaching earthquake: high-frequency fluctuations in the earth's crust, water levels in wells, fluctuations in magnetic fields.

Grozny

According to the same department of seismology, a major earthquake in the period from 2017 to 2036. may occur in the North Caucasus, on the border of Chechnya and Dagestan. In contrast to the situation in Kamchatka, no work is being carried out to reduce the possible damage from earthquakes, which can lead to a greater number of human casualties than if such work were carried out.

NY

New research results by American seismologists from Columbia University indicate a high seismic hazard at the present time in the vicinity of New York. The magnitude of the earthquake could reach five points, which could lead to the complete destruction of old buildings in the city. Another cause for concern was the nuclear power plant, located right at the intersection of two faults, ie. in an extremely dangerous region. Its destruction could make New York a second Chernobyl.

Banda Aceh

Indonesia is located in the most seismically active zone of the planet, and therefore you will not surprise anyone here with earthquakes. In particular, the island of Sumatra, constantly turns out to be almost right at the epicenter of tremors. An exception will not be a new earthquake predicted by seismologists, with an epicenter 28 km from the city of Banda Aceh, which will occur in the next six months.

Bucharest

The strongest earthquake in Romania can be provoked by blasting in shale rocks carried out in the Carpathian Mountains. Geophysicists from Romanian national institute report that the epicenter of the future earthquake will be in the same place, at a depth of 40 kilometers. The fact is that work to search for shale gas in these layers of the earth can cause displacements of the earth's crust and, as a result, earthquakes.

The strongest earthquakes throughout the history of mankind caused enormous material damage and caused a huge number of casualties among the population. The first mention of tremors date back to 2000 BC.
And despite the achievements of modern science and the development of technology, no one can still predict exact time when the elements strike, so it often becomes impossible to quickly and timely evacuate people.

Earthquakes are natural disasters that kill the most people, much more than, for example, hurricanes or typhoons.
In this rating, we will talk about the 12 most powerful and destructive earthquakes in the history of mankind.

12. Lisbon

November 1, 1755, in the capital of Portugal, the city of Lisbon, there was a strong earthquake, later called the Great Lisbon Earthquake. It was a terrible coincidence that on November 1, All Saints Day, thousands of residents gathered for mass in the churches of Lisbon. These churches, like other buildings throughout the city, could not withstand the powerful shocks and collapsed, burying thousands of unfortunate people under their rubble.

Then a 6-meter tsunami wave poured into the city, covering the survivors, rushing in panic along the streets of the destroyed Lisbon. The destruction and loss of life was enormous! As a result of the earthquake, which lasted no more than 6 minutes, caused by a tsunami and numerous fires that engulfed the city, at least 80,000 residents of the capital of Portugal died.

Many famous figures and philosophers dealt with this deadly earthquake in their works, for example, Immanuel Kant, who tried to find scientific explanation such a massive tragedy.

11. San Francisco

On April 18, 1906, at 5:12 am, powerful tremors shook the sleeping San Francisco. The force of the shocks was 7.9 points and as a result of a strong earthquake in the city, 80% of the buildings were destroyed.

After the first count of the dead, the authorities reported 400 victims, but later their number increased to 3,000 people. However, the main damage to the city was caused not by the earthquake itself, but by the monstrous fire caused by it. As a result, more than 28,000 buildings were destroyed throughout San Francisco, and property damage amounted to more than $ 400 million at the rate of that time.
Many residents themselves set fire to their dilapidated houses, which were insured against fire, but not against earthquakes.

10. Messina

The largest earthquake in Europe was the earthquake in Sicily and Southern Italy, when on December 28, 1908, as a result of the most powerful tremors with a force of 7.5 on the Richter scale, according to various experts, from 120 to 200,000 people died.
The epicenter of the disaster was the Strait of Messina, located between the Apennine Peninsula and Sicily, the city of Messina suffered the most, where there was practically not a single surviving building left. A huge tsunami wave, caused by tremors and reinforced by an underwater landslide, also brought a lot of destruction.

Documented fact: rescuers were able to pull two malnourished, dehydrated, but alive children from the rubble, 18 days after the disaster! Numerous and extensive destruction was caused primarily by the poor quality of buildings in Messina and other parts of Sicily.

Russian sailors provided invaluable assistance to the residents of Messina Imperial Navy. The ships as part of the training group sailed the Mediterranean and on the day of the tragedy ended up in the port of Augusta in Sicily. Immediately after the tremors, the sailors organized a rescue operation and thanks to their courageous actions, thousands of residents were saved.

9. Haiyuan

One of the deadliest earthquakes in human history was the devastating earthquake that hit Haiyuan County in Gansu Province on December 16, 1920.
Historians estimate that at least 230,000 people died that day. The strength of the tremors was such that entire villages disappeared in the faults of the earth's crust, such large cities as Xi'an, Taiyuan and Lanzhou were very badly damaged. Incredibly, but strong waves formed after the impact of the elements were recorded even in Norway.

Modern researchers believe that the death toll was much higher and totals at least 270,000 people. At that time, it was 59% of the population of Haiyuan County. Several tens of thousands of people died from the cold after their homes were destroyed by the elements.

8. Chile

The earthquake in Chile on May 22, 1960, is considered the strongest earthquake in the history of seismology, the magnitude of the tremors was 9.5 on the Richter scale. The earthquake was so powerful that it caused tsunami waves over 10 meters high, covering not only the coast of Chile, but also causing great damage to the city of Hilo in Hawaii, and some of the waves reached the coast of Japan and the Philippines.

More than 6,000 people died, most of them hit by the tsunami, the destruction was unimaginable. 2 million people were left without housing and shelter, and the amount of damage amounted to more than 500 million dollars. In some areas of Chile, the impact of the tsunami wave was so strong that many houses were blown 3 km inland.

7. Alaska

On March 27, 1964, the most powerful earthquake in American history hit Alaska. The strength of the rumors was 9.2 on the Richter scale and this earthquake became the strongest since the elements struck in Chile in 1960.
129 people died, of which 6 were unfortunate victims of the tremors, the rest were washed away by a huge tsunami wave. The elements caused the greatest destruction in Anchorage, and tremors were registered in 47 US states.

6. Kobe

The earthquake in Kobe, Japan on January 16, 1995 was one of the most devastating in history. Tremors with a force of 7.3 began at 05:46 am local time and continued for several days. As a result, more than 6,000 people died, 26,000 were injured.

The damage done to the infrastructure of the city was simply enormous. More than 200,000 buildings were destroyed, 120 out of 150 berths were destroyed in the port of Kobe, and there was no power supply for several days. The total damage from the impact of the elements amounted to about 200 billion dollars, which at that time was 2.5% of Japan's total GDP.

Not only government services rushed to help the affected residents, but also the Japanese mafia - the yakuza, whose members delivered water and food to the victims of the disaster.

5. Sumatra

On December 26, 2004, the strongest tsunami that hit the coasts of Thailand, Indonesia, Sri Lanka and other countries was caused by a devastating earthquake measuring 9.1 on the Richter scale. The epicenter of the tremors was in the Indian Ocean, near the island of Simeulue, off the northwestern coast of Sumatra. The earthquake was unusually large, there was a shift of the earth's crust at a distance of 1200 km.

The height of the tsunami waves reached 15-30 meters and according to various estimates, from 230 to 300,000 people became victims of the disaster, although it is impossible to calculate the exact number of deaths. Many people were simply washed away into the ocean.
One of the reasons for this number of victims was the lack of a system early warning in the Indian Ocean, through which it was possible to inform the local population about the approaching tsunami.

4. Kashmir

On October 8, 2005, in the Kashmir region, which is under the control of Pakistan, there was the strongest earthquake in South Asia in the last hundred years. The force of the tremors was 7.6 on the Richter scale, which is comparable to the San Francisco earthquake in 1906.
According to official data, 84,000 people died as a result of the disaster, according to unofficial data, more than 200,000. Rescue work was hampered by the military conflict between Pakistan and India in the region. Many villages and villages were completely wiped off the face of the earth, and the city of Balakot in Pakistan was also completely destroyed. In India, 1300 people became victims of the earthquake.

3. Haiti

On January 12, 2010, an earthquake measuring 7 on the Richter scale hit Haiti. The main blow fell on the capital of the state - the city of Port-au-Prince. The consequences were terrible: almost 3 million people were left homeless, all hospitals and thousands of residential buildings were destroyed. The number of victims was simply enormous, according to various estimates from 160 to 230,000 people.

Criminals who escaped from the prison destroyed by the elements poured into the city, cases of looting, robberies and robberies became frequent on the streets. The material damage from the earthquake is estimated at 5.6 billion dollars.

Despite the fact that many states - Russia, France, Spain, Ukraine, the USA, Canada and dozens of others - provided all possible assistance in eliminating the consequences of the elements of Haiti, more than five years after the earthquake, more than 80,000 people still live in makeshift camps for refugees.
Haiti is the poorest country in the western hemisphere and this natural disaster dealt an irreparable blow to the economy and the standard of living of citizens.

2. Earthquake in Japan

On March 11, 2011, the strongest earthquake in Japanese history struck the Tohoku region. The epicenter was located east of the island of Honshu and the strength of the tremors was 9.1 on the Richter scale.
As a result of the disaster, the nuclear power plant in the city of Fukushima was badly damaged and power units at reactors 1, 2, and 3 were destroyed. Many areas became uninhabitable as a result of radioactive radiation.

After underwater tremors, a huge tsunami wave covered the coast and destroyed thousands of administrative and residential buildings. More than 16,000 people died, 2,500 are still considered missing.

The material damage also turned out to be colossal - more than 100 billion dollars. And given that it may take years to completely restore the destroyed infrastructure, the amount of damage can increase several times.

1. Spitak and Leninakan

There are many tragic dates in the history of the USSR, and one of the most famous is the earthquake that shook the Armenian SSR on December 7, 1988. The most powerful tremors in just half a minute almost completely destroyed the northern part of the republic, capturing the territory where more than 1 million inhabitants lived.

The consequences of the disaster were monstrous: the city of Spitak was almost completely wiped off the face of the Earth, Leninakan was badly damaged, more than 300 villages were destroyed and 40% of the industrial capacities of the republic were destroyed. More than 500 thousand Armenians were left homeless, according to various estimates, from 25,000 to 170,000 people died, 17,000 citizens were left disabled.
111 states and all the republics of the USSR provided assistance in the restoration of destroyed Armenia.

The territory of Russia, in comparison with other states located in seismically active regions, is generally characterized by moderate seismicity. But even in our country there are places where it “shakes” a lot, and therefore it can be extremely dangerous to live.

Kuriles and Sakhalin

The Kuril Islands and Sakhalin are part of the volcanic Fire Belt of the Pacific Ocean. In fact, the Kuriles are the tops of volcanoes rising above the surface of the ocean, and volcanoes played an important role in the formation of Sakhalin. Every day, seismic stations record tremors in the area.
On the night of May 28, 1995, the largest earthquake in Russia in the last hundred years occurred on Sakhalin. Neftegorsk was completely destroyed. Despite the fact that the intensity of the shocks barely exceeded 7 points under the 12-point scale, large-block earthquake-resistant houses collapsed. 2040 people died, more than 700 were injured. The real tragedy was that on this day the high school students had a graduation. The building where the school ball was held collapsed, burying the graduates under it.
As always during earthquakes, rescuers recorded miraculous cases of rescue. For example, one man fell into the basement of a house, where he was able to eat the remaining pickles for many days, and survived.

Kamchatka

The peninsula is also part of the volcanic belt of the Pacific Ocean. There are 29 active volcanoes in Kamchatka and dozens of "dormant" volcanoes. Small shocks associated with tectonic processes and volcanic activity are recorded every day. Fortunately, most earthquakes occur at sea and in sparsely populated areas.
An 8.5-magnitude earthquake that occurred on November 4, 1952 in the Avacha Bay was included in the 15 most powerful earthquakes of the 20th century and was called the "Great Kamchatka". It caused a tsunami that washed away Severo-Kurilsk and reached Japan, Alaska, the Hawaiian Islands and even Chile.
After that, a network of seismic stations was created in the Far East.

North Caucasus and the Black Sea coast

For the danger of this region, the inhabitants should “thank” the Arabian plate, which collides with the Eurasian one. Seismologists call the area difficult: Crimea-Caucasus-Kopetdag zone of Iran-Caucasus-Anatolian seismically active region. There are often earthquakes of magnitude 9 and above. On the Russian side, the territories of Dagestan, Chechnya, Ingushetia and North Ossetia are considered dangerous.
The largest events are called the nine-magnitude earthquake in Chechnya in 1976 and the Chkhalta earthquake in 1963. Everyone who was born in the USSR remembers the Armenian Spitak, where 25,000 people died.
Restless and in Stavropol. Tremors are felt in the cities of Anapa, Novorossiysk and Sochi. The great Crimean earthquake of 1927 is described in the famous novel "The Twelve Chairs".

Lake Baikal is located in the middle of a huge rift zone - a break in the earth's crust. Up to 5-6 thousand shocks are recorded here per year. On the rift line extending to Mongolia, there is also a “valley of dormant volcanoes” on the Okinsky plateau in Buryatia.
The most famous earthquake in Lake Baikal, the Tsaganskoye, occurred on January 12, 1863. Then, on the southeastern shore of Lake Baikal, a whole valley went under water, and Proval Bay was formed.
The last strong earthquake occurred on August 27, 2008. The epicenter was in the southern waters of Lake Baikal, the strength was 10 points. In Irkutsk it was felt 6-7 points. People panicked, ran out into the street, collapsed cellular. In Baikalsk, where it was felt up to 9 points, the work of the pulp and paper mill was interrupted.
Fortunately, most of the strong earthquakes in this region do not lead to casualties, since the area is sparsely populated, and multi-storey buildings are designed for tremors.

Altai and Tyva

Complex processes lead to earthquakes both in Altai and Tuva. On the one hand, the region is influenced by the huge plate of Hindustan, due to the movement of which to the north the Himalayas were formed, on the other hand, the Baikal Fault. Seismic activity in the region is increasing.
A 10-magnitude earthquake that occurred on September 27, 2003 made a lot of noise in Altai. It has reached Novosibirsk, Kuzbass and Krasnoyarsk. Six districts of the republic suffered, the village of Beltir was destroyed, 110 families were left homeless. Buildings were destroyed in the settlements of Kosh-Agach and Aktash.
In Tuva, the local population was frightened by the earthquake that occurred on the evening of December 27, 2011. In the villages of the republic, houses cracked and collapsed. Chandeliers swayed in the homes of residents of Abakan and Novokuznetsk. Fear was added by the fact that it was freezing cold outside. Seismic activity continued almost all winter. So, in February 2012, seismologists counted more than 700 shocks.

There are two seismically dangerous belts in Yakutia, a huge area. The northern one goes from the Lena delta to the Sea of ​​Okhotsk along the Chersky ridge, the southern one - Baikal-Stanovoi stretches from Baikal to the Sea of ​​\u200b\u200bOkhotsk. There are two or three shocks here every day. The strongest earthquake is the nine-magnitude Oymyakon earthquake of 1971. Tremors were felt on the territory of a million square kilometers and reached Magadan. And in April 1989, between the valleys of the Lena and Amur rivers, an earthquake of 8 points occurred on an area of ​​\u200b\u200bone and a half million square kilometers! The Yakuts themselves claim that the republic accounts for almost a third of all seismic activity in Russia.

For 300 years, 42 earthquakes with a magnitude of 3 to 6.5 have been recorded in the Urals.
Recent studies suggest that tremors up to 7 points are possible here. True, this happens once every 110-120 years. There is an increase in seismic activity right now.
The last strong earthquake occurred on March 30, 2010 near Kachkanar. At the epicenter, the force of the shocks was 5 points. Windows trembled in houses, car alarms went off in cars.

Of course, for those who live in the central regions, what is happening on the outskirts of Russia will seem far away, but it turns out that there are events that affect the entire country. So, on May 24, 2013, at the bottom of the Sea of ​​Okhotsk, at a depth of 620 kilometers, there was a push with a force of 8 points. The earthquake was unique: it swept across the country and, becoming the fourth in Western Russia over the past 76 years.
This earthquake brought a lot of thrills to the inhabitants of the capital's skyscrapers. Some offices have evacuated workers.