Which countries have the most destructive earthquakes. Record depth at which the epicenter of the earthquake was recorded. What to do in case of earthquakes

Recently I helped my little son with a small report on this topic. Despite the fact that I know enough about this phenomenon, the discovered information turned out to be extremely interesting. I will try to accurately convey the essence of the topic and talk about how How are earthquakes classified?. By the way, the son proudly brought five from school. :)

Where do earthquakes occur

First you need to understand what is commonly called an earthquake. So, scientifically speaking, these are strong vibrations on the surface of our planet, due to the processes that take place in the lithosphere. Areas where high mountains are located are the places where this phenomenon is observed most often. The thing is that the surfaces in these areas are at the stage of formation, and bark is most mobile. Such areas are called places. rapidly changing relief, however, many earthquakes were observed on the plains.

What are earthquakes

Science distinguishes several types of this phenomenon:

• tectonic;
• collapse;
• volcanic.

Earthquake of a tectonic type- a consequence of the displacement of mountain plates, which is due to the collision of two platforms: continental and oceanic. This species is characterized formation of mountains or depressions, as well as surface vibrations.

As for earthquakes volcanic type, then they are due to the pressure of gases and magma on the surface from below. Usually the shocks are not very strong, however can go on long enough. Tellingly, this species is a harbinger of a more destructive and dangerous phenomenon - volcanic eruptiona.

Landslide earthquake occurs as a result of the formation of voids, which can be formed by movement groundwater. In this case the surface just collapses, which is accompanied by small tremors.

Intensity measurement

According to Richter scale it is possible to classify an earthquake based on the energy that is carried seismic waves. It was proposed in 1937 and eventually spread throughout the world. So:

1. not felt- shocks are not caught at all;
2. very weak- is registered only by devices, a person does not feel;
3. weak- can be felt while in the building;
4. intensive- accompanied by a slight displacement of objects;
5. almost strong- felt in open spaces by sensitive people;
6. strong- felt by all people;
7. very strong- small cracks appear in the brickwork;
8. destructive- serious damage to buildings;
9. devastating- huge destruction;
10. destroying- dips in the ground up to 1 meter are formed;
11. catastrophic- buildings are destroyed to the foundation. Cracks over 2 meters;
12. catastrophe- the entire surface is indented with cracks, rivers change their channels.

According to seismologists - scientists who study this phenomenon, about 400,000 events per year earthquakes of various strengths.

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 lithospheric plates, volcanic eruptions, explosions). The consequences of shocks of 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, cracks form on the earth's surface, 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 activities. 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 shocks, a large tsunami rose 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 fluctuations (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 much attention to them. 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 shudders occurring on one side of the planet shake opposite side. For example, a magnitude 9.3 earthquake in the Indian Ocean in 2004 eased some of the increasing 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 big number people (in the 16th century 830 thousand people died, in the middle of the last century - 240 thousand).

Such catastrophic consequences could have been prevented if earthquake protection had been well thought out at the state level, and the possibility of strong earthquakes was taken into account in the design of buildings: most people died under the rubble. Often, people living or staying in a seismically active zone do not have the slightest idea of ​​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 elevators are strictly forbidden to use.

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 bearing wall, or crawl under sturdy table by protecting your head 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, you need to urgently leave vehicle. 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 danger of such a natural phenomenon as an earthquake is estimated by most seismologists in points. There are several scales by which the strength of seismic tremors is assessed. The scale adopted in Russia, Europe and the CIS countries was developed in 1964. According to the data from the 12-point scale, the greatest destructive force is characteristic of an earthquake of 12 points, and such strong tremors as "strong catastrophe" are qualified. There are also other methods for measuring the strength of shocks that take into account fundamentally different moments - the area on which the shocks occurred, the time of "shaking" and other factors. However, no matter what yardstick measures the strength of tremors, there are natural disasters that are among the most terrible.

The strength of earthquakes: has it ever been 12 points?

Since the Kamori scale was taken into consideration, and this made it possible to assess natural disasters that have not yet disappeared into the dust of centuries, there have been at least 3 earthquakes with a magnitude of 12.

1. Tragedy in Chile, 1960.
2. Destruction in Mongolia, 1957
3. Tremors in the Himalayas, 1950.

In first place in the ranking, which contains the most powerful earthquakes in the world, is the 1960 cataclysm, known as the "Great Chile earthquake." The scale of destruction is estimated at the maximum known 12 points, while the magnitude of the earth's vibrations exceeded 9.5 points. The strongest earthquake in history occurred in May 1960 in Chile, near several cities. Valdivia became the epicenter, where the fluctuations reached a maximum, but the population was alerted to the impending danger, since the day before the tremors were felt in the nearby provinces of Chile. 10 thousand people are considered dead in this terrible disaster, a lot of people were swept away by the tsunami that began, but experts say that without prior notification of the victims, there could have been many times more. By the way, many people were saved due to the fact that a lot of people went to churches for Sunday services. At the moment of the beginning of the shaking, people were in the temples, which survived.

The most devastating earthquakes in the world include the Gobi-Altai disaster that swept through Mongolia on December 4, 1957. As a result of the tragedy, the earth was literally turned inside out: breaks were formed, demonstrating such geological processes that are not visible under normal circumstances. The high mountains in the mountain ranges ceased to exist, the peaks collapsed, the habitual pattern of the mountains was broken.

The tremors in populated areas were on the rise and continued for quite a long time, until they reached 11-12 points. People managed to leave their homes seconds before total destruction. Dust flying from the mountains covered the cities of the southern part of Mongolia for 48 hours, visibility did not exceed several tens of meters.

Another terrible cataclysm, estimated by seismologists at 11-12 points, happened in the Himalayas, in the highlands of Tibet, in 1950. The terrible trace of the earthquake in the form of mudflows and landslides changed the topography of the mountains beyond recognition. With a terrible roar, the mountains formed like paper, and dust clouds spread from the epicenter to a radius of up to 2000 km.

Tremors from time immemorial: what do we know about ancient earthquakes?

The largest earthquakes that have occurred in modern times discussed and well covered in the media.

Thus, they are still well known, the memory of them, of the victims and destruction is still fresh. But what about earthquakes that happened a long time ago - a hundred, two hundred or three hundred years ago? Traces of destruction have long been eliminated, and witnesses either survived the incident or died. Nevertheless, historical literature contains traces of the most terrible earthquakes in the world that occurred long ago. So, in the annals that record the largest earthquakes in the world, it is written that in ancient times the tremors happened much more often than now, and were much stronger. According to one such source, in 365 BC there were shocks that affected the entire Mediterranean territory, as a result of which the seabed was exposed before the eyes of eyewitnesses.

Deadly earthquake for one of the Wonders of the World

One of the most famous ancient earthquakes is the destruction of 244 BC. In those days, according to scientists, tremors happened much more often, but it is this earthquake that is especially famous: as a result of tremors, the statue of the legendary Colossus of Rhodes collapsed. This statue, according to ancient sources, was one of the eight Wonders of the World. It was a giant lighthouse in the form of a statue of a man with a torch in his hand. The statue was so huge that a flotilla could swim between its spread legs. Dimensions played a trick on the Colossus: the legs were too fragile to withstand seismological activity, and the Colossus collapsed.

Iranian earthquake in 856

The death of hundreds of thousands of people as a result of even not very strong earthquakes was a common occurrence: there were no systems for predicting seismic activity, no warning, no evacuation. So, in 856, more than 200 thousand people became victims of shocks in the North of Iran, the city of Damkhan was wiped off the face of the earth. By the way, the record number of victims for this one earthquake is comparable to the number of victims of earthquakes in Iran for the rest of the time, until today.

The bloodiest earthquake in the world

The Chinese earthquake of 1565, which destroyed the provinces of Gansu and Shaanxi, claimed the lives of more than 830 thousand people. This is an absolute record for the number of human casualties, which has not been exceeded to this day. In history, it remained as the "Great Jiajing Earthquake" (after the name of the emperor who was then in power). Historians estimate its power at 7.9 - 8 points, as evidenced by geological surveys.

Here is how this phenomenon was described in the annals:
“In the winter of 1556, a catastrophic earthquake struck Shaanxi and the provinces around it. Our Hua County has suffered numerous misfortunes and misfortunes. Mountains and rivers changed their location, roads were destroyed. In some places, the earth suddenly rose, and new hills appeared, or vice versa - parts of the former hills went underground, swam and became new plains. In other places, mudflows constantly descended, or the earth split, and new ravines appeared. Private houses, public buildings, temples and city walls collapsed with lightning speed and completely ".

Cataclysm for All Saints Day in Portugal

A terrible tragedy that claimed the lives of more than 80 thousand Portuguese occurred in Lisbon on November 1, 1755. This cataclysm is not included in the most powerful earthquakes in the world either in terms of the number of victims or in terms of the strength of seismic activity. But the terrible irony of fate with which this phenomenon broke out is shocking: the tremors began precisely when people went to celebrate the holiday in the church. The temples of Lisbon could not stand it and collapsed, burying a huge number of unfortunate people under them, and then a 6-meter tsunami wave covered the city, killing the rest of the people who were on the streets.

The largest earthquakes in the history of the twentieth century

Ten catastrophes of the 20th century, which claimed the greatest number of lives and brought the most terrible destruction, are reflected in the summary table:

Tangshan-1976

The events in China in 1976 are captured in Feng Xiaogang's film Catastrophe. Despite the relative weakness of the magnitude, the disaster claimed a large number of lives, the first shock provoked the destruction of 90% of residential buildings in Tangshan. The hospital building disappeared without a trace, the open ground literally swallowed up the passenger train.

Sumatra 2004, the largest in the geographical sense

The 2004 Sumatran earthquake affected several countries: India, Thailand, South Africa, Sri Lanka. The exact number of victims cannot be calculated, since the main destructive force - the tsunami - carried tens of thousands of people into the ocean. This is the largest earthquake in terms of geography, since its prerequisites were the movement of plates in the Indian Ocean, followed by shocks at a distance of up to 1600 km. The ocean floor rose as a result of the collision of the Indian and Burmese plates, tsunami waves ran in all directions from the fault of the plates, which rolled thousands of kilometers and reached the coast.

Haiti 2010, our time

Haiti experienced its first major earthquake in 2010 after an almost 260-year lull. The national fund of the republics received the greatest damage: the entire center of the capital with its rich cultural heritage, all administrative and government buildings were damaged. More than 232,000 people died, many of whom were swept away by the tsunami. The consequences of the disaster were a surge in the incidence of intestinal diseases and an increase in crime: shocks destroyed prison buildings, which the prisoners immediately took advantage of.

The most powerful earthquakes in Russia

In Russia, there are also dangerous seismically active regions in which an earthquake can occur. However, most of these Russian territories are remote from densely populated areas, which excludes the possibility of major destruction and casualties.

The largest earthquakes in Russia, however, are also inscribed in the tragic history of the struggle between the elements and man.

Among the worst earthquakes in Russia:

• North Kuril destruction in 1952.
• Neftegorsk destruction in 1995.

Kamchatka-1952

Severo-Kurilsk was completely destroyed as a result of aftershocks and a tsunami on November 4, 1952. Unrest in the ocean, 100 km from the coast, brought to the city waves of 20 meters in height, hour after hour washing the coast and washing coastal settlements into the ocean. A terrible stream demolished all the buildings and killed more than 2 thousand people.

Sakhalin-1995

On March 27, 1995, the elements took only 17 seconds to wipe out the working settlement of Neftegorsk in the Sakhalin Region. More than 2 thousand inhabitants of the village died, which accounted for 80% of the inhabitants. Large-scale destruction did not allow the settlement to be restored, so locality became a ghost: a memorial plate was installed in it, telling about the victims of the tragedy, and the residents themselves were evacuated.

A dangerous area in Russia in terms of seismic activity is any region at the junction of tectonic plates:

• Kamchatka and Sakhalin,
• Caucasian republics,
• Altai region.

In any of these regions, the likelihood of a natural earthquake remains, since the mechanism for the generation of earthquakes has not yet been studied.

Nature Under the earthquake refers to tremors and vibrations of the earth's surface, which are caused by natural or artificial causes. Today, an earthquake is one of the most difficult to predict and dangerous natural phenomena.

About a million earthquakes occur on our planet every year, but the vast majority of them are so weak that only special instruments (seismographs) register them.

Earthquakes cause rapid displacements of parts of the earth's crust. An earthquake begins with the movement of rocks or a gap in the depths of the earth's crust. This place is called the focus of an earthquake. Most often it is located at a depth of up to 100 kilometers, but sometimes the depth reaches 700 kilometers. The area of ​​land that is located above the focus of an earthquake is called the epicenter and experiences tremors of maximum strength. Seismic waves propagate from the source of the earthquake in all directions, which gradually fade in the process of removal ( this process similar to the propagation of sound waves). The speed of propagation of seismic waves can reach 8 kilometers per second.

Most often, earthquakes occur at the bottom of the oceans, which is associated with a small thickness of the earth's crust in this area. These earthquakes are completely safe if they do not cause destructive tsunamis.

Earthquake forecasting is currently underway. This issue is most relevant for regions located at the junction of lithospheric plates, since the vast majority of destructive earthquakes occur here.

An earthquake can be caused not only by nature, but also by man. It is noted that tectonic activity is increasing in the areas of construction of large reservoirs, mining natural gas and oil, the construction of large metropolitan areas from imported materials and the development a large number rocks from quarries and mines. The reason for this is a violation of the natural balance and a change in pressure in the rocks.

Earthquakes are a natural phenomenon that even today attracts the attention of scientists not only due to their little knowledge, but also due to their unpredictability, which can harm humanity.

An earthquake is an earth tremor that can be felt by a person to a large extent, depending on the power of the earth's surface vibrations. Earthquakes are not uncommon and occur every day in different parts of the world.

Often, most earthquakes occur at the bottom of the oceans, which avoids catastrophic destruction within densely populated cities.

The principle of earthquakes

What causes earthquakes?

Earthquakes can be caused by both natural causes and man-made ones.

Most often, earthquakes occur due to faults in tectonic plates and their rapid displacement. For a person, the fault is not noticeable until the moment when the energy generated from the rupture of rocks begins to break out to the surface.

How do earthquakes occur due to unnatural causes?

Quite often, a person, through his negligence, provokes the appearance of artificial shocks, which in their power are not at all inferior to natural ones. Among these reasons are the following:

• — explosions;
• — overfilling of reservoirs;
• - ground (underground) nuclear explosion;
• mine collapses.

The place where the tectonic plate breaks is the focus of the earthquake. Not only the strength of the potential shock, but also its duration will depend on the depth of its location.

If the focus is located 100 kilometers from the surface, then its strength will be more than palpable. Most likely, this earthquake will entail the destruction of houses and structures.

Originating in the sea, such earthquakes cause tsunamis.

Where do earthquakes most often occur?

However, the focus can be located much deeper - 700 and 800 kilometers. Such phenomena are not dangerous and can be recorded only with the help of special instruments - seismographs.

The place where an earthquake manifests highest power, is called the epicenter.

It is this piece of land that is considered the most dangerous for the existence of all living things.

Studying earthquakes

A detailed study of the nature of earthquakes makes it possible to prevent many of them and make the life of the population living in dangerous places, more relaxed.

To determine the power and measure the strength of an earthquake, two basic concepts are used:

• — magnitude;
• - intensity;

The magnitude of an earthquake is a measure that measures the energy released during release from the source in the form of seismic waves.

The magnitude scale allows you to accurately determine the sources of fluctuations.

The intensity is measured in points and allows you to determine the ratio of the magnitude of shocks and their seismic activity from 0 to 12 points on the Richter scale.

Features and signs of earthquakes

Regardless of what causes an earthquake and in what area it is localized, its duration will be approximately the same.

One push on average lasts 20-30 seconds. But there are cases in history when a single push without repetition could last up to three minutes.

Signs of an approaching earthquake are the anxiety of animals, who, having sensed the slightest vibrations of the earth's surface, try to get away from the unfortunate place away.

Other signs of an imminent earthquake are:

• - the appearance of characteristic clouds in the form of oblong ribbons;
• — change of water level in wells;
• - failures in the operation of electrical equipment, mobile phones.

How to behave during earthquakes?

How to behave during an earthquake to save your life?

• - Maintain composure and calmness;
• - When indoors, never hide under fragile furniture, such as under a bed.

  Lie next to them in a fetal position and cover your head with your hands (or protect your head with something extra). When the roof collapses, it will fall on the furniture and a layer may form, in which you will find yourself. It is important to choose sturdy furniture whose widest part rests on the floor, i.e. this furniture cannot fall;

• - While outdoors, move away from tall buildings and structures, power lines that can collapse.
• - Cover your mouth and nose with a wet cloth to prevent dust and fumes from entering in case of fire of any object.

If you notice an injured person in a building, then wait for the tremors to end and only then make your way into the room.

Otherwise, both people may be trapped.

Where there are no earthquakes and why?

Earthquakes occur when tectonic plates break. Therefore, countries and cities located on a solid tectonic plate without faults can not worry about their safety.

Australia is the only continent in the world that is not located at the junction of lithospheric plates.

There are no active volcanoes and high mountains on it and, accordingly, there are no earthquakes. There are also no earthquakes in Antarctica and Greenland.

The presence of the enormous gravity of the ice shell prevents the spread of tremors over the surface of the earth.

The likelihood of earthquakes in the area Russian Federation quite high in rocky terrain, where the displacement and movement of rocks is most actively observed.

Thus, high seismicity is noted in the North Caucasus, Altai, Siberia and the Far East.

Report: Earthquakes

Earthquakes are tremors and vibrations of the earth's surface resulting from sudden displacements and ruptures in the earth's crust or the upper part of the mantle and are transmitted over long distances in the form of vibrations. The intensity of earthquakes is estimated in seismic points, magnitude is used for the energy classification of earthquakes (see Richter scale). The most famous catastrophic earthquakes: Lisbon 1755, California 1906, Messina 1908, Ashgabat 1948, Chile 1960, Armenian 1988, Iranian 1990.

General information

Strong earthquakes are catastrophic, yielding in the number of victims only to typhoons and significantly (tens of times) ahead of volcanic eruptions.

The material damage of one devastating earthquake can amount to hundreds of millions of dollars. The number of weak earthquakes is much greater than the number of strong ones. So, out of hundreds of thousands of earthquakes that occur annually on Earth, only a few are catastrophic. They release about 1020 J of potential seismic energy, which is only 0.01% of the thermal energy of the Earth radiated into outer space.

Where and why do earthquakes occur?

The territorial distribution of earthquakes is uneven.

It is determined by the movement and interaction of lithospheric plates.

Earthquake

The main seismic belt, in which up to 80% of all seismic energy is released, is located in the Pacific Ocean in the region of deep-sea trenches, where cold lithospheric plates are moving under the continent. The rest of the energy is released in the Eurasian fold belt at the collision sites of the Eurasian plate with the Indian and African plates and in the areas of mid-ocean ridges under conditions of lithosphere extension (see Fig.

Rift world system).

Earthquake parameters

Earthquake sources are located at depths of up to 700 km, but most of the seismic energy (3/4) is released in sources located at depths of up to 70 km. The size of the focus of catastrophic earthquakes can reach 100 × 1000 km. Its position and the place where the masses begin to move (hypocenter) are determined by recording seismic waves that occur during earthquakes (for weak earthquakes, the focus and hypocenter coincide).

The projection of the hypocenter onto the earth's surface is called the epicenter. Around it is the area of ​​greatest destruction (epicentral, or pleistoseist, area).

Earthquake intensity

The intensity of the manifestation of earthquakes on the surface is measured in points and depends on the depth of the source and the magnitude of the earthquake, which serves as a measure of its energy.

Maximum known value magnitude approaches 9. The magnitude is related to the total energy of the earthquake, but this dependence is not direct, but logarithmic, with an increase in magnitude per unit, the energy increases 100 times, i.e., with a shock with a magnitude of 6, 100 times more energy is released than with magnitude 5, and 10,000 more than at magnitude 4. Often in the media reporting on seismic disasters, the magnitude scale (Richter scale) and the seismic intensity scale measured in seismic points, i.e., are identified.

j. Journalists reporting 12 on the Richter scale confuse magnitude with intensity. The intensity is the greater, the closer the source is located to the surface, so, for example, if the source of an earthquake with a magnitude of 8 is located at a depth of 10 km, then on the surface the intensity will be 11-12 points; with the same magnitude, but at a depth of 40-50 km, the impact on the surface decreases to 9-10 points.

seismic scales

Seismic movements are complex, but classifiable.

There are a large number of seismic scales that can be reduced to three main groups. In Russia, the most widely used 12-point scale MSK-64 (Medvedev-Sponheuer-Karnik) in the world, dating back to the Merkali-Kankani scale (1902), is used in countries Latin America the 10-point Rossi-Forel scale (1883) was adopted, in Japan - a 7-point scale.

The assessment of intensity, which is based on the everyday consequences of an earthquake, easily distinguishable even by an inexperienced observer, is different in the seismic scales of different countries. For example, in Australia, one of the degrees of shaking is compared with “like a horse rubbing against a veranda post”, in Europe the same seismic effect is described as “bells begin to ring”, in Japan there is an “overturned stone lantern”.

In the simplest and most convenient form, sensations and observations are presented in a schematized short descriptive scale (MSK variant) that anyone can use.

Point - Manifestation on the surface

1 - Not felt by anyone, recorded only by seismic instruments

2 - Felt sometimes by people who are in a calm state

3 - Felt by few, more pronounced indoors on higher floors

4 - Felt by many (especially indoors), at night some wake up.

Possible ringing of dishes, rattling of glasses, slamming of doors

5 - Felt by almost everyone, many wake up at night. Swinging hanging objects, cracks in window panes and plaster

6 - Felt by everyone, plaster crumbles, light destruction of buildings

7 - Cracks in the plaster and chipping of individual pieces, thin cracks in the walls. Shocks are felt in cars

8 - Large cracks in the walls, falling pipes, monuments.

Cracks on steep slopes and on damp soil

9 - Collapse of walls, roof slabs in some buildings, breaks in underground pipelines

10 - The collapse of many buildings, the curvature of the railroad tracks.

Landslides, collapses, cracks (up to 1 m) in the ground

11 - Numerous wide cracks in the ground, landslides in the mountains, collapse of bridges, only a few stone buildings remain stable

12 - Significant changes in the relief, deviation of the flow of rivers, objects thrown into the air, total destruction of structures

How far does an earthquake affect

Strong earthquakes can be felt at a distance of a thousand or more kilometers.

Thus, in aseismic Moscow, shocks with an intensity of up to 3 points are observed from time to time, serving as an “echo” of catastrophic Carpathian earthquakes in the Vrancea mountains in Romania, the same earthquakes in Moldova, close to Romania, are felt as 7-8 points.

Earthquake duration

The duration of earthquakes is different, often the number of tremors forms a swarm of earthquakes, including previous (foreshocks) and subsequent (aftershocks) shocks.

The distribution of the strongest shock (the main earthquake) within the swarm is random. The magnitude of the strongest aftershock is 1.2 less than that of the main shock, these aftershocks are accompanied by their secondary series of subsequent shocks.

For example, an earthquake that occurred on about. Lissa in the Mediterranean, lasted three years, total number shocks for the period 1870-73 amounted to 86 thousand.

catastrophic earthquakes

Of the huge number of earthquakes that occur annually, only one has a magnitude equal to or greater than 8, ten - 7-7.9, one hundred - 6-6.9.

Any earthquake with a magnitude of St. 7 could be a major disaster. However, it can also go unnoticed if it occurs in a desert area. Thus, the grandiose natural disaster - the Gobi-Altai earthquake (1957; magnitude 8.5, intensity 11-12 points) - remains almost unexplored, although due to the enormous force, small depth of the source and lack of vegetation cover, this earthquake left on the surface the most a complete and diverse picture (2 lakes appeared, a huge overthrust in the form of a stone wave up to 10 m high instantly formed, the maximum displacement along the normal fault reached 300 m, etc.).

P.). An area 50-100 km wide and 500 km long (like Denmark or Holland) was completely destroyed. If this earthquake had occurred in a densely populated area, the number of victims could have been measured in the millions. The consequences of one of the strongest earthquakes (magnitude could be 9), which occurred in the oldest region of Europe - Lisbon - in 1755 and captured the territory of over 2.5 million km2, were so grandiose (50 thousand out of 230 thousand people died).

townspeople, a rock grew in the harbor, the coastal bottom became dry land, the outline of the coast of Portugal changed) and impressed the Europeans so much that Voltaire responded to him with the “Poem about the death of Lisbon” (1756, Russian translation 1763). Apparently, the impression of this catastrophe was so strong that Voltaire in the poem challenged the doctrine of pre-established world harmony.

Strong earthquakes, no matter how rare they are, never leave contemporaries indifferent. Thus, in W. Shakespeare's tragedy "Romeo and Juliet" (1595), the nurse recalls the earthquake of 1580, which, apparently, the author himself experienced.

Why do people die in earthquakes?

If earthquakes occur at sea, they can cause destructive waves - tsunamis, which most often devastate coasts. Pacific Ocean, as happened in 1933 in Japan and in 1952 in Kamchatka.

The total number of victims of earthquakes on the planet over the past 500 years has amounted to about 5 million people.

people, almost half of them are in China. So in 1556 in the Chinese Prov. An earthquake with a magnitude of 8.1 killed 830,000 people in Shaanxi; according to official Chinese data (according to American seismologists, up to 1 million people). Exceptionally severe consequences are also connected with the earthquakes in 1737 in Calcutta (India), when 300,000 people died.

people, in 1908 in Messina (Italy) - 120 thousand people, in 1923 in Tokyo - 143 thousand people.

Large losses during earthquakes are usually associated with high density population, primitive construction methods, especially characteristic of poor areas, while it is not at all necessary that the earthquake be strong (for example, in 1960, up to 15 thousand people died as a result of a seismic shock with a magnitude of 5.8).

man in Agadir, Morocco). Natural phenomena - landslides, cracks play a smaller role. The catastrophic consequences of an earthquake can be prevented by improving the quality of buildings, since most of the people die under their rubble. It is also useful to take advice - during an earthquake, do not run out into the street, but rather take cover in doorway or under a sturdy slab or plank (table) capable of supporting the weight of the collapsing load.

Forecast and zoning of earthquakes

The problem of earthquake forecasting based on observations of precursors (predicting not only the place but, most importantly, the time of a seismic event) is far from being solved, because

to. none of the harbingers can be considered reliable. Isolated cases of extremely successful timely forecasts are known, for example, in 1975 in China, an earthquake with a magnitude of 7.3 was very accurately predicted. In earthquake-prone areas, the construction of earthquake-resistant structures plays an important role (see.

anti-seismic construction). The division of the territory according to the degree of potential seismic hazard is part of the task of seismic zoning. It is based on the use of historical data (on the recurrence of seismic events, their strength) and instrumental observations of earthquakes, geological and geographical mapping and information about the movement of the earth's crust.

The zoning of the territory is also connected with the problem of insurance against earthquakes.

Seismograph

Instrumental observations first appeared in China, where in 132 Chang Heng invented a seismoscope, which was a skillfully made vessel.

On the outside vessel, with a pendulum placed inside, the heads of dragons were engraved in a circle, holding balls in their mouths. When the pendulum was swinging from an earthquake, one or more balls fell into the open mouths of the frogs, placed at the base of the vessels so that the frogs could swallow them.

A modern seismograph is a set of instruments that register ground vibrations during an earthquake and convert them into an electrical signal recorded on seismograms in analog and digital form. However, as before, the main sensitive element is a pendulum with a load.

seismic service

Permanent observations of earthquakes are carried out by the seismic service.

The modern world network includes St. 2000 stationary seismic stations, whose data are systematically published in seismological bulletins and catalogs.

In addition to stationary stations, expeditionary seismographs are used, including those installed at the bottom of the oceans. Expeditionary seismographs were also sent to the Moon (where 5 seismographs annually record up to 3000 moonquakes), as well as to Mars and Venus.

Anthropogenic earthquakes

20th century man-made human activity, which has taken on a planetary scale, has become the cause of induced (artificially induced) seismicity, which occurs, for example, during nuclear explosions (tests at the Nevada test site initiated thousands of seismic shocks), during the construction of reservoirs, the filling of which sometimes provokes strong earthquakes.

This happened in India, when the construction of the Koyna reservoir caused an 8-magnitude earthquake, in which 177 people died.

Studying earthquakes

Seismology is the study of earthquakes.

Seismic waves generated during earthquakes are also used to study internal structure Earth, achievements in this area served as the basis for the development of seismic survey methods.

Earthquakes have been observed since ancient times. Detailed historical descriptions, reliably testifying to earthquakes from ser.

1 thousand BC e., given by the Japanese. Great attention was also paid to seismicity by ancient scientists - Aristotle and others. Systematic instrumental observations begun in the 2nd half. 19th century led to the separation of seismology into an independent science (B.

B. Golitsyn, E. Wiechert, B. Gutenberg, A. Mohorovichich, F. Omori and others).

EARTHQUAKE MAGNITUDE (from lat. magnitudo - magnitude), a conditional value that characterizes the total energy of elastic vibrations caused by earthquakes or explosions; allows you to compare the sources of oscillations by their energy.

SEISMIC SCALE, a scale for assessing the intensity of an earthquake on the Earth's surface. The Russian Federation uses the 12-point seismic scale MSK-64.

mid-ocean ridges, mountain structures that form at the bottom of the oceans single system encircling the entire globe.

LITHOSPHERIC PLATE, large (several thous.

km in diameter) a block of the earth's crust, including not only the continental, but also the oceanic crust associated with it; bounded on all sides by seismically and tectonically active fault zones.

HYPOCENTRE, the point of the beginning of the movement of masses (rupture rupture) in the source of the earthquake. Depth up to 700 km.

2017 Reference books. Mobile version.

12-point scale of intensity, strength of earthquakes

Earthquake intensity — quality characteristic the degree of destruction and other manifestations on the earth's surface, at a specific point on the earth's surface.

How does an earthquake happen

For this, a twelve-point scale is used, in contrast to the nine-point magnitude scale (Richter scale), which quantitatively characterizes the energy in the earthquake source.

Earthquake gradation by strength (intensity, seismic effect):

One point - minimal seismicity, not felt by people.

Two points (very weak) - weak vibrations are noticeable on the upper floors of high-rise buildings.

The reason may be man-made, from a loaded truck passing under the windows.

Three ball. (weak) - chandeliers swing.

Score four (moderate) - Shaking is felt inside buildings.

Five points (strong) - vibrations are felt both in the building and on the street.

Six points - furniture moves and falls, dishes bounce, burst window panes.

People, frightened, run out of the buildings into the street.

Seven points (very strong) - it is difficult to stand on your feet, the walls are cracking brick houses, flights of stairs and ceilings of buildings fall, landslides and cracks appear on roads, in winter ice cracks on rivers and reservoirs.

There is an additional danger - fires, accidents, short circuits.

Eight points. (destructive) - brick buildings are collapsing, underground communications are torn.

Nine points (destructive) - cracks form in the soil, on rivers and in reservoirs - great excitement.

Ten points. (destructive) - asphalt on the roads is crushed and broken, cracks in the ground - up to a meter wide, landslides and collapses.

Eleven points (catastrophic) - brick houses almost all are destroyed, the roads are badly damaged.

Twelve points (catastrophic) - the earth's surface is changing; cracks in the earth's crust reach a width of up to 10-15m, depth - up to 10m or more, closing or remaining open during the next shocks; the amplitude of vertical oscillations of the soil reaches half a meter; large areas they settle and can be flooded, or rise up - with an amplitude of up to several tens of meters or more; displacement occurs along the faults.

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earthquake called tremors and vibrations of the planet's surface that occur in the upper layers of the lithosphere due to a sharp displacement of the lithospheric plates. The least dangerous of them are formed in the Earth's mantle (at great depths). But ruptures and displacements of the surface layer can bring with them catastrophic destruction.

This is explained by a decrease in the strength of earthquakes with distance from its source. The deeper the focus is, the smaller the oscillations occur on the earth's surface.

The strength of earthquakes in points

The focus of an earthquake (the place where it formed) is also called the focus or hypocenter.

From it diverge in all directions seismic waves, like waves on water arising from a thrown pebble, with the only difference that seismic waves are directed both to the sides, and up, and down. But that place on the earth's surface, which is located directly above the hearth itself, is called earthquake epicenter. As a rule, the strongest vibrations occur precisely in it.

The magnitude scale is able to assess the strength of this destructive phenomenon nature.

To be more precise, it estimates the energy that is released in the form of seismic waves. And this value fluctuates 1 to 9.5(it is usually used by scientists, for example, in the popular film "The San Andreas Fault" the magnitude reaches a maximum value of 9.5).
But although this characteristic is quite eloquent, nevertheless, this is not enough to understand how dangerous a cataclysm is.

After all, it happens that a weaker, but prolonged earthquake causes much more damage than a strong one. Therefore, there is also a scale of intensity. It evaluates the impact of vibrations on the earth's surface, as well as their consequences.

To assess this destructive phenomenon, various scales are used, but, as a rule, they are all 12-point. The most popular magnitude scale is Richter scale. If we compare it with the intensity scale, then we can roughly imagine the consequences of earthquakes of various strengths:

• 1-2 points - it is noted only on devices, although especially sensitive people can feel weak tremors.
• 3-4 points - felt by almost everyone as light shocks, especially noticeable inside buildings (by light rattling of objects and shaking).
• 5-6 points - quite strong fluctuations occur, during which cracks may appear in old houses, plaster crumbles, objects fall from shelves, etc.
• 7-8 points - very strong vibrations are observed, leading to the destruction of houses and the appearance of cracks in the ground.
• 9-10 points - a devastating earthquake, leading to the destruction of buildings, landslides and collapses, huge cracks in the earth's surface, etc.

  Phenomena of such strength are observed about 10 times a year.

• 11-12 points - a catastrophic earthquake, the devastating consequences of which are difficult to predict. They usually happen once a year.

The consequences of earthquakes

Strong earthquakes can destroy buildings and various structures. As a result of such destruction, many people die.

And if the source is in the sea, then a tsunami hits the coast ( huge wave capable of destroying everything in its path). An earthquake is one of the most dangerous phenomena on our planet. And given that they are almost impossible to predict, like many other phenomena ... This becomes a real problem.

Earthquakes. Why earthquakes happen

Earthquake statistics

As we already know, earthquakes with a magnitude of 7-12 are called dangerous. It is they who are able to lead to destruction and change in the relief of the planet. And although it is impossible to say exactly how many such phenomena occur annually, we can calculate the approximate number of the most powerful of them.

Two centuries ago, for example, there were about 40 earthquakes a year with a strength of 7 or more. Now their number has increased tenfold. 400 strong earthquakes a year for the Earth have already become the norm. The trend is impressive, isn't it? And what will happen next?

earthquakes

Earthquakes are tremors accompanied by vibrations of the earth's surface.

Causes and types

The location of earthquake sources practically coincides with the boundaries of lithospheric plates

Earthquakes are tectonic, volcanic and landslide.

Tectonic earthquakes arise due to sharp displacements of mountain plates or as a result of the withdrawal of an oceanic platform under the mainland.

After all, the surface of the earth consists of continental and oceanic platforms, which, in turn, consist of separate blocks. When the blocks are on top of each other, they can rise up and mountains are formed, or they can go down and depressions are formed, or one of the plates will go under the other.

All these processes are accompanied by vibrations or tremors of the earth.

Volcanic earthquakes occur due to the fact that flows of hot lava and gases press from below on the surface of the Earth and thus make you feel that the earth is moving away from under your feet. Volcanic earthquakes are usually not very strong, but can last quite a long time, sometimes several weeks.

Often such earthquakes warn of an imminent volcanic eruption, which is even more dangerous than the earthquake itself.

Sometimes voids form under the ground, for example, under the influence of ground water or underground rivers that erode the earth. In these places, the ground cannot withstand its own weight and collapses, causing a slight shaking.

It is called landslide earthquake.

After strong earthquakes, the landscape of the area changes, new lakes and mountains may appear

The most destructive and terrible are tectonic earthquakes. The place where a collision of plates or a powerful explosion occurs, associated with the release of energy accumulated in the earth, is called earthquake focus, or hypocenter.

When the explosion occurs, a shock wave with a speed of more than 5 km / s (depending on the power of the explosion) begins to spread in all directions, reaches the surface of the earth (this area on the surface is called the epicenter, and it is located directly above the hypocenter) and diverges to the sides along circles.

In the epicenter, the most severe destruction occurs, and on the outskirts of the area affected by the earthquake, people may not even feel anything.

The strength of earthquakes

Earthquakes are one of the most dangerous natural phenomena. They bring great destruction and disaster, destroying not only material values, but also all living things, including people.

The strength of an earthquake on the earth's surface is measured in points on a special 12-point scale.

Destruction after a strong earthquake

Point scale for measuring the strength of an earthquake:

• 1 point - Not felt.

  It is noted only by special devices

• 2 point - Very weak, noted only by pets and some people in the upper floors of buildings
• 3 ball - Weak. Only felt inside some buildings, like a concussion when driving a truck
• 4 ball - Moderate. You can hear the creaking of floorboards, beams, the clinking of dishes, the trembling of furniture.

  Inside the building, shaking is felt by most people.

• 5 ball - Pretty strong. In the rooms, shocks are felt as from the fall of heavy objects. Window panes burst, chandeliers and furniture sway
• 6 ball - Strong. Heavy furniture sways, dishes break, books fall from shelves, only very dilapidated houses are destroyed.
• 7 ball - Very strong.

  Old houses are destroyed. Cracks appear in strong buildings, plaster crumbles. Cloudy water in rivers and lakes

• 8 ball - Destructive. Trees sway violently, strong fences break. Many strong buildings are destroyed. Cracks appear in the soil
• 9 ball - Devastating. Strong buildings are destroyed.

  earthquakes

  Significant cracks appear in the soil

• 10 ball - Destroying. Even strong buildings and bridges are destroyed. Landslides and collapses, cracks and bends in the soil occur
• 11 ball - Catastrophe. Almost all stone buildings, roads, dams, bridges are destroyed. Shear cracks form on the surface of the earth
• 12 ball - Strong catastrophe. All structures are destroyed, the whole area is devastated.

  riverbeds are changing

Seismology

The pen of a seismograph draws a curved line in the form of sharp zigzags when tremors begin

Earthquakes are studied by science seismology. AT different countries world scientists conduct observations of the behavior of the earth's crust. In this they are helped by special devices - seismographs.

They measure and automatically record the slightest shaking occurring anywhere the globe. When the earth's surface fluctuates, the main part of the seismograph - the suspended load - due to inertia moves relative to the base of the device, and the recorder records the seismic signal transmitted to the marker.

An important task of seismology is the prediction of earthquakes.

Unfortunately, modern science cannot yet accurately predict them. Seismologists can more or less reliably determine the area and strength of an earthquake, but it is very difficult to predict its beginning.

Can an earthquake rock the earth?

In mid-May 1960, one of the most significant and destructive earthquakes occurred in Chile - the Great Chilean Earthquake.

Despite the fact that the main ground vibrations occurred in the southwestern part of South America - the epicenter of the earthquake was located near the city of Valdivia - their "echoes" reached other territories of our planet: in particular, the Hawaiian Islands and Japan. The phenomenon in which an earthquake that occurred in one part of the earth causes other parts of it to pulsate and tremble, even those located thousands of kilometers from the epicenter, is called the "swing" or "vibration" of the earth.

In this article, we will look at causes of earthquakes. The very concept of an earthquake is known to all people, and even children, but what are the reasons that suddenly the earth under your feet begins to move and everything around collapses?

First of all, it must be said that earthquakes are conditionally divided into several types: tectonic, volcanic, landslide, artificial and man-made. We will briefly review all of them right now. If you want to know, be sure to read to the end.

1. Tectonic causes of earthquakes

Most often, earthquakes occur due to the fact that they are in constant motion. Upper layer lithospheric plates are called tectonic plates. By themselves, the platforms move unevenly and constantly put pressure on each other. However, they remain dormant for a long time.

Gradually, the pressure builds up, as a result of which the tectonic platform makes a sudden push. It is he who produces vibrations of the surrounding rock, which is why an earthquake occurs.

San Andreas Fault

Transform Rifts are huge cracks in the Earth where platforms "rub" against each other. Many readers should be aware that the San Andreas Fault is one of the most famous and longest transform faults in the world. It is located in California in the USA.

Platforms moving along it cause devastating earthquakes in the cities of San Francisco and Los Angeles. Interesting fact: In 2015, Hollywood released a film called "The San Andreas Fault". He talks about the corresponding catastrophe.

1. Volcanic causes of earthquakes

Volcanoes are one of the causes of earthquakes. Although they do not produce strong ground vibrations, they last long enough. The causes of the tremors are related to the fact that deep in the depths of the volcano, tension is growing, formed by lava and volcanic gases. As a rule, volcanic earthquakes last weeks and even months.

However, history knows cases of tragic earthquakes of this type. An example is the Krakatoa volcano located in Indonesia, which erupted in 1883.

The force of its explosion was at least 10 thousand times greater than the force. The mountain itself was almost completely destroyed, and the island broke into three small parts. Two-thirds of the land disappeared under water, and the rising tsunami destroyed everyone who still had a chance to escape. More than 36,000 people died.

1. Landslide causes of earthquakes

Earthquakes caused by giant landslides are called landslides. They have a local character, and their strength, as a rule, is small. But even here there are exceptions. For example, in Peru, in 1970, a landslide, with a volume of 13 million cubic meters, descended from Mount Huascaran at a speed of over 400 km / h. About 20,000 people died.

1. Man-made causes of earthquakes

Earthquakes of this type are caused by human activity. For example, artificial reservoirs in places not intended for this by nature provoke pressure on the plates with their weight, which serves to increase the number and strength of earthquakes.

The same applies to the oil and gas industry, when a large amount of natural materials. In a word, man-made earthquakes occur when a person took something from nature from one place, and transferred it without asking to another.

1. Man-made causes of earthquakes

By the name of this type of earthquake, it is easy to guess that the fault for it lies entirely with the person.

For example, in 2006 North Korea experienced nuclear bomb, which caused a small earthquake recorded in many countries. That is, any activity of the inhabitants of the earth, which is obviously guaranteed to entail an earthquake, is an artificial cause of this type of disaster.

Can earthquakes be predicted?

Indeed it is possible. For example, in 1975, Chinese scientists predicted an earthquake and saved many lives. But it is impossible to do this with a 100% guarantee even today. An ultra-sensitive device that registers an earthquake is called a seismograph. On a spinning drum, the recorder marks the vibrations of the earth.

Animals before earthquakes also acutely feel anxiety. Horses begin to rear up for no apparent reason, dogs bark strangely, and snakes crawl out of their holes to the surface.

Earthquake scale

As a rule, the strength of earthquakes is measured by the Earthquake Scale. We will give all twelve points so that you have an idea of ​​\u200b\u200bwhat it is.

• 1 point (imperceptible) - the earthquake is recorded exclusively by instruments;
• 2 points (very weak) - can only be seen by pets;
• 3 points (weak) - noticeable only in some buildings. Feelings like driving a car over bumps;
• 4 points (moderate) - noticed by many people, can cause windows and doors to move;
• 5 points (quite strong) - glass rattles, hanging objects sway, old whitewash may crumble;
• 6 points (strong) - with this earthquake, light damage to buildings and cracks in low-quality buildings are already noted;
• 7 points (very strong) - at this stage, the buildings suffer significant damage;
• 8 points (destructive) - there are destructions in buildings, chimneys and cornices fall, cracks of several centimeters can be seen on the slopes of the mountains;
• 9 points (devastating) - earthquakes cause collapses of some buildings, old walls collapse, and the crack propagation speed reaches 2 centimeters per second;
• 10 points (destructive) - collapses in many buildings, in most - serious destruction. The soil is streaked with cracks up to 1 meter wide, landslides and landslides all around;
• 11 points (catastrophe) - large collapses in the mountains, numerous cracks and a picture of the general destruction of most buildings;
• 12 points (strong catastrophe) - the relief is globally changing almost before our eyes. Huge collapses and total destruction of all buildings.

Basically twelve. point scale earthquakes, you can evaluate any catastrophe caused by tremors of the earth's surface.