Seismically active regions of Russia: where earthquakes are possible. Earthquakes

20% of the territory of Russia belongs to seismically active areas (including 5% of the territory is subject to extremely dangerous 8-10 magnitude earthquakes).

Over the past quarter century, about 30 significant earthquakes, that is, with a magnitude of more than seven on the Richter scale, have occurred in Russia. 20 million people live in zones of possible destructive earthquakes in Russia.

Residents of the Far Eastern region of Russia suffer the most from earthquakes and tsunamis. The Pacific coast of Russia is located in one of the “hottest” zones of the “Ring of Fire”. Here, in the area of ​​transition from the Asian continent to the Pacific Ocean and the junction of the Kuril-Kamchatka and Aleutian island volcanic arcs, more than a third of Russia’s earthquakes occur, 30 active volcanoes, including such giants as Klyuchevskaya Sopka and Shiveluch. It has the highest density of distribution of active volcanoes on Earth: for every 20 km of coastline there is one volcano. Earthquakes occur here no less often than in Japan or Chile. Seismologists usually count at least 300 significant earthquakes per year. On the seismic zoning map of Russia, the areas of Kamchatka, Sakhalin and the Kuril Islands belong to the so-called eight- and nine-point zone. This means that in these areas the intensity of shaking can reach 8 and even 9 points. Destruction may also result. The most destructive earthquake measuring 9.0 on the Richter scale occurred on Sakhalin Island on May 27, 1995. About 3 thousand people died, the city of Neftegorsk, located 30 kilometers from the epicenter of the earthquake, was almost completely destroyed.

Seismically active regions of Russia also include Eastern Siberia, where 7-9 point zones are distinguished in the Baikal region, Irkutsk region and the Buryat Republic.

Yakutia, through which the boundary of the Euro-Asian and North American plates passes, is not only considered a seismically active region, but is also a record holder: earthquakes with epicenters north of 70° N often occur here. As seismologists know, the bulk of earthquakes on Earth occur near the equator and in mid-latitudes, and in high latitudes such events are recorded extremely rarely. For example, on the Kola Peninsula, many different traces of high-power earthquakes have been discovered - mostly quite old. The forms of seismogenic relief discovered on the Kola Peninsula are similar to those observed in earthquake zones with an intensity of 9-10 points.

Other seismically active regions of Russia include the Caucasus, spurs of the Carpathians, and the coasts of the Black and Caspian Seas. These areas are characterized by earthquakes with a magnitude of 4-5. However, for historical period Catastrophic earthquakes with a magnitude greater than 8.0 were also noted here. Traces of a tsunami were also found on the Black Sea coast.

However, earthquakes can also occur in areas that cannot be called seismically active. On September 21, 2004, two series of tremors with a force of 4-5 points were recorded in Kaliningrad. The epicenter of the earthquake was 40 kilometers southeast of Kaliningrad near the Russian-Polish border. According to maps of general seismic zoning of the territory of Russia, the Kaliningrad region belongs to a seismically safe area. Here the probability of exceeding the intensity of such tremors is about 1% within 50 years.

Even residents of Moscow, St. Petersburg and other cities located on the Russian Platform have reason to worry. On the territory of Moscow and the Moscow region, the last of these seismic events with a magnitude of 3-4 occurred on March 4, 1977, on the nights of August 30-31, 1986 and May 5, 1990. The strongest known seismic tremors in Moscow, with an intensity of over 4 points, were observed on October 4, 1802 and November 10, 1940. These were “echoes” of larger earthquakes in the Eastern Carpathians.

Earthquakes are scary a natural phenomenon, which can bring numerous troubles. They are associated not only with destruction, which may result in human casualties. Caused by them catastrophic waves tsunamis can lead to even more disastrous consequences.

Which areas of the world are most affected by earthquakes? To answer this question, you need to look at where the active seismic areas are. These are zones earth's crust, which are more mobile than their surrounding regions. They are on the borders lithospheric plates where large blocks collide or move apart It is the movements of powerful rock layers that cause earthquakes.

Dangerous areas of the world

There are several belts on the globe that are characterized by a high frequency of underground impacts. These are seismically dangerous areas.

The first of them is usually called the Pacific Ring, since it occupies almost the entire ocean coast. Not only earthquakes are frequent here, but also volcanic eruptions, which is why the name “volcanic” or “ring of fire” is often used. The activity of the earth's crust here is determined by modern mountain-building processes.

The second large seismic belt stretches along the high young of the Alps and other mountains Southern Europe and to the Sunda Islands via Asia Minor, Caucasus, mountains of the Middle and Central Asia and the Himalayas. The collision of lithospheric plates also occurs here, which causes frequent earthquakes.

The third belt stretches across the entire Atlantic Ocean. This is the Mid-Atlantic Ridge, which is the result of the spreading of the earth's crust. Iceland, known primarily for its volcanoes, also belongs to this belt. But earthquakes here are by no means a rare phenomenon.

Seismically active regions of Russia

Earthquakes also occur in our country. Seismically active regions of Russia are the Caucasus, Altai, the mountains of Eastern Siberia and Far East, Commander and Kuril Islands, o. Sakhalin. Tremors of great force can occur here.

One can recall the Sakhalin earthquake of 1995, when two-thirds of the population of the village of Neftegorsk died under the rubble of destroyed buildings. After the rescue work, it was decided not to restore the village, but to relocate the residents to other settlements.

In 2012-2014, several earthquakes occurred in the North Caucasus. Fortunately, their sources were located at great depths. There were no casualties or serious damage.

Seismic map of Russia

The map shows that the most seismically dangerous areas lie in the south and east of the country. At the same time, the eastern parts are relatively sparsely populated. But in the south, earthquakes pose a much greater danger to people, since the population density here is higher.

Irkutsk, Khabarovsk and some others big cities find themselves in the danger zone. These are active seismic areas.

Anthropogenic earthquakes

Seismically active areas occupy approximately 20% of the country's territory. But this does not mean that the rest is completely insured against earthquakes. Tremors with a force of 3-4 points are observed even far from the boundaries of lithospheric plates, in the center of platform areas.

At the same time, with the development of the economy, the possibility of anthropogenic earthquakes increases. They are most often caused by the collapse of the roof of underground voids. Because of this, the earth's crust seems to shake, almost like a real earthquake. And there are more and more voids and cavities underground, because people extract oil from the depths for their needs and natural gas, pumps out water, builds mines for the extraction of solid minerals... And underground nuclear explosions generally comparable in strength to natural earthquakes.

The collapse of rock layers in itself can pose a danger to people. Indeed, in many areas, voids form directly under populated areas. Recent events in Solikamsk have only confirmed this. But even a weak earthquake can lead to dire consequences, because as a result it can destroy structures that are in disrepair, dilapidated housing in which people continue to live... Also, violation of the integrity of rock layers threatens the mines themselves, where collapses can occur.

What to do?

People are not yet able to prevent such a terrible phenomenon as an earthquake. And they haven’t even learned to predict exactly when and where it will happen. This means you need to know how you can protect yourself and your loved ones during tremors.

People living in such dangerous areas should always have an earthquake plan in place. Since a disaster may find family members in different places, there should be an agreement on a meeting place after the tremors stop. The home should be as safe as possible from falling heavy objects; it is best to attach furniture to the walls and floor. All residents should know where they can urgently turn off gas, electricity, and water in order to avoid fires, explosions and electric shocks. Stairs and passages should not be cluttered with things. Documents and a certain set of products and essentials should always be at hand.

Starting from kindergartens and schools, the population needs to be taught correct behavior in case of a natural disaster, which will increase the chances of rescue.

Seismically active regions of Russia present special requirements both industrial and civil engineering. Earthquake-resistant buildings are more difficult and expensive to build, but the cost of their construction is nothing compared to the lives saved. After all, not only those who are in such a building will be safe, but also those nearby. There will be no destruction and rubble - there will be no casualties.

Hundreds of thousands of earthquakes occur on our planet every year. 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 shakes violently enough to destroy everything around it.

Since most tremors of such force occur at the bottom of the World Ocean, unless they are accompanied by a tsunami, people are not even aware of them. But when the land shakes, the disaster is so destructive that the number of victims runs into the thousands, as happened in the 16th century in China (more than 830 thousand people died during earthquakes of magnitude 8.1).

Earthquakes are underground tremors and vibrations of the earth's crust caused by natural or artificially created causes (movement of lithospheric plates, volcanic eruptions, explosions). The consequences of high-intensity tremors are often catastrophic, second only to typhoons in terms of the number of victims.

Unfortunately, at the moment, scientists have not studied the processes that occur in the depths of our planet so well, and therefore the forecast of earthquakes is rather approximate and inaccurate. Among the causes of earthquakes, experts identify tectonic, volcanic, landslide, artificial and man-made vibrations of the earth's crust.

Tectonic

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

Although this shift is usually small, amounting to only a few centimeters, the mountains located above the epicenter begin to move, releasing enormous 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 vibrations, although weak, continue for a long time. Usually they do not pose any particular danger, but catastrophic consequences have still been recorded. As a result powerful eruption Krakatoa volcano at the end of the 19th century. the explosion destroyed half the mountain, and the subsequent tremors were so powerful that they split the island into three parts, plunging two-thirds into the abyss. The tsunami that arose after this destroyed absolutely everyone who had managed to survive before and did not have time to leave the dangerous territory.

Landslide

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

Technogenic

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 water penetrating through the soil begins to destroy it. In addition, an increase in seismic activity has been noticed 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 moderate earthquakes.

An undersea earthquake occurs when tectonic plates collide on the ocean floor or near the coast. If the source is shallow and the magnitude is 7, an underwater earthquake is extremely dangerous because it causes a tsunami. During the shaking of the sea crust, one part of the bottom falls, 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 moving towards the coast.

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

The tremors begin

The source of an earthquake is a rupture, 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, resulting in friction and energy that gradually begins to accumulate.

When the stress reaches its maximum and begins to exceed the frictional force, the rocks rupture, after which the released energy is converted into seismic waves moving at a speed of 8 km/s and causing vibrations in the earth.

The characteristics of earthquakes based on 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 of the Pacific Rim. The deeper the epicenter, the further 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 vibrations (foreshocks), and after it, aftershocks and subsequent tremors begin, 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 thousand tremors.

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 several years ago, lasted forty seconds - and this was enough to turn the city of Port-au-Prince into ruins. But in Alaska, a series of tremors were recorded that shook the earth for about seven minutes, with three of them leading to significant destruction.

Calculating which shock will be the main one and will have the greatest magnitude is extremely difficult, problematic, and there are no absolute methods. Therefore, strong earthquakes often take the population by surprise. This, for example, happened in 2015 in Nepal, in a country where mild tremors were recorded so often that people simply did not pay attention to them special attention. Therefore, a ground shaking with a magnitude of 7.9 led to a large number of victims, and the weaker aftershocks with a magnitude of 6.6 that followed it 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, the 2004 magnitude 9.3 earthquake in the Indian Ocean relieved some of the increasing stress on the San Andreas Fault, which is located at the junction of lithospheric plates along the California coast. It turned out to be so strong that it slightly modified the appearance of our planet, smoothing out its bulge in the middle part and making it more rounded.

What is magnitude

One way 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 very often confused with a twelve-point intensity scale, measured in points). An increase in the magnitude of earthquakes by just one unit means an increase in the amplitude of vibrations by ten, and energy by thirty-two times.

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

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

• 2 – weak, almost imperceptible vibrations;
• 4 - 5 - even though the shocks are weak, they can lead to minor damage;
• 6 – medium damage;
• 8.5 - one of the strongest recorded earthquakes.
• The largest is considered to be the Great Chilean earthquake with a magnitude of 9.5, which generated a tsunami that, having crossed the Pacific Ocean, reached Japan, covering 17 thousand kilometers.

Focusing on the magnitude of earthquakes, scientists claim that out of the tens of thousands of vibrations that occur on our planet per year, only one has a magnitude of 8, ten - from 7 to 7.9, and a hundred - from 6 to 6.9. It must be taken into account that if the earthquake magnitude is 7, the consequences can be catastrophic.

Intensity scale

To understand why earthquakes occur, scientists have developed an intensity scale based on external manifestations such as the impact on people, animals, buildings, and nature. The closer the epicenter of earthquakes is 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 would be between eleven and twelve. 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 intensity scale, the first destruction can occur already with magnitude six shocks, when thin cracks appear in the plaster. An earthquake of eleven magnitude is considered catastrophic (the surface of the earth's crust becomes covered with cracks, buildings are destroyed). The strongest earthquakes, capable of significantly changing the appearance of the area, are estimated at twelve points.

What to do during earthquakes

According to rough estimates by scientists, the number of people who have died in the world due to earthquakes over the past half-millennium exceeds five million people. Half of them are in China: it is located in a zone of seismic activity, and people live on its territory 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 design of buildings had taken into account the possibility of strong tremors: 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 conditions emergency and how you can save your life.

You need to know that if tremors catch you in a building, you need to do everything possible to get out into the open space as quickly as possible, and you absolutely cannot use elevators.

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

If a person finds himself on the street during the onset of earthquakes, he must move away from the house by 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 as possible from tattered electrical wires industrial enterprises, since explosive materials or toxic substances may be stored there.

But if the first tremors caught a person while he was in a car or public transport, he urgently needs to leave vehicle. If the car is in an open area, on the contrary, stop the car and wait out the earthquake.

If it so happens that you are completely covered in 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 strongest earthquakes throughout human history have caused colossal material damage and caused a huge number of casualties among the population. The first mention of tremors dates back to 2000 BC.
And despite the achievements modern science and the development of technology, no one can still predict the exact time when the disaster will 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 human history.

12. Lisbon

On November 1, 1755, a powerful earthquake occurred in the capital of Portugal, the city of Lisbon, later called the Great Lisbon Earthquake. A terrible coincidence was 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 unfortunates under their rubble.

Then a 6-meter tsunami wave rushed into the city, covering the surviving people rushing in panic through the streets of destroyed Lisbon. The destruction and loss of life were colossal! As a result of the earthquake, which lasted no more than 6 minutes, the tsunami it caused and numerous fires that engulfed the city, at least 80,000 residents of the Portuguese capital died.

Many famous figures and philosophers touched on this deadly earthquake in their works, for example, Immanuel Kant, who tried to find a scientific explanation for such a large-scale tragedy.

11. San Francisco

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

After the first count of the dead, 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 it caused. As a result, more than 28,000 buildings throughout San Francisco were destroyed, with property damage amounting to more than $400 million at the exchange 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 powerful tremors measuring 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 practically not a single surviving building remained. brought a lot of destruction and huge wave tsunami caused by tremors and amplified by an underwater landslide.

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

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

9. Haiyuan

One of the deadliest earthquakes in human history was the devastating earthquake that struck Haiyuan County, part of Gansu Province, on December 16, 1920.
Historians estimate that at least 230,000 people died that day. The force of the tremors was such that entire villages disappeared into the faults of the earth’s crust, and large cities such as Xi’an, Taiyuan and Lanzhou were greatly damaged. Incredibly, strong waves formed after the disaster were recorded even in Norway.

Modern researchers believe that the death toll was much higher and totaled at least 270,000 people. At that time, this 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, considered the strongest earthquake in the history of seismology, measured 9.5 on the Richter scale. The earthquake was so powerful that it caused tsunami waves more than 10 meters high, which covered not only the coast of Chile, but also caused enormous damage to the city of Hilo in Hawaii, and some of the waves reached the coasts of Japan and the Philippines.

More than 6,000 people died, most of whom were hit by the tsunami, and the destruction was unimaginable. 2 million people were left homeless and the damage amounted to more than $500 million. In some areas of Chile, the impact of the tsunami wave was so strong that many houses were carried away 3 km inland.

7. Alaska

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

6. Kobe

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

The damage caused to the city's infrastructure was simply enormous. More than 200,000 buildings were destroyed, 120 of the 150 berths in the port of Kobe were destroyed, and there was no power supply for several days. The total damage from the disaster was about $200 billion, 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 those affected by the disaster.

5. Sumatra

On December 26, 2004, a powerful tsunami that hit the shores 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; the earth's crust shifted 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 the exact number of deaths is impossible to calculate. Many people were simply washed into the ocean.
One of the reasons for such a number of victims was the lack of an early warning system in the Indian Ocean, with which it was possible to inform the local population of the approaching tsunami.

4. Kashmir

On October 8, 2005, the worst earthquake to hit South Asia in a century occurred in the Pakistani-administered Kashmir region. The strength of the tremors was 7.6 on the Richter scale, which is comparable to the San Francisco earthquake in 1906.
As a result of the disaster, according to official data, 84,000 people died, according to unofficial data, more than 200,000. Rescue efforts have been hampered by military conflict between Pakistan and India in the region. Many villages were completely wiped off the face of the earth, and the city of Balakot in Pakistan was also completely destroyed. In India, the earthquake killed 1,300 people.

3. Haiti

On January 12, 2010, an earthquake measuring 7.0 on the Richter scale occurred in 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 had escaped from a prison destroyed by the elements poured into the city; cases of looting, robberies and robberies became frequent on the streets. Material damage from the earthquake is estimated at 5.6 billion dollars.

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

2. Earthquake in Japan

On March 11, 2011, the strongest earthquake in Japanese history occurred in 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 severely 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 was also colossal - more than $100 billion. And considering that on full recovery It may take years for the infrastructure to be destroyed, and the amount of damage may 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. 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 severely damaged, more than 300 villages were destroyed and 40% of the republic’s industrial capacity was destroyed. More than 500 thousand Armenians were left homeless, according to various estimates, from 25,000 to 170,000 residents died, 17,000 citizens remained disabled.
111 states and all republics of the USSR provided assistance in the restoration of destroyed Armenia.

The content of the article

EARTHQUAKES, vibrations of the Earth caused by sudden changes in the condition of the planet's interior. These vibrations are elastic waves propagating at high speed through the rock mass. The most powerful earthquakes are sometimes felt at distances of more than 1,500 km from the source and can be recorded by seismographs (special highly sensitive instruments) even in the opposite hemisphere. The area where vibrations originate is called the earthquake source, and its projection onto the Earth's surface is called the earthquake epicenter. The sources of most earthquakes lie in the earth's crust at depths of no more than 16 km, but in some areas the depths of the sources reach 700 km. Thousands of earthquakes occur every day, but only a few of them are felt by humans.

Mentions of earthquakes are found 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 heavily flavored with superstition and theories based on scanty and unreliable observations. A. Perry (France) began a series of systematic descriptions (catalogues) of earthquakes in 1840. In the 1850s, R. Malle (Ireland) compiled a large catalog of earthquakes, and his detailed report on the Naples earthquake in 1857 became one of the first strictly scientific descriptions of large earthquakes.

Causes of earthquakes.

Although numerous studies have been carried out since ancient times, it cannot be said that the causes of earthquakes have been fully studied. Based on the nature of the processes at their sources, several types of earthquakes are distinguished, the main ones being tectonic, volcanic and man-made.

Tectonic earthquakes

arise as a result of a sudden release of stress, for example, during movement along a fault in the earth’s crust (research in recent years shows that deep earthquakes can also be caused by phase transitions in the Earth’s mantle, occurring at certain temperatures and pressures). Sometimes deep faults come to the surface. During 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 sudden movements of 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

can be caused by underground nuclear tests, filling reservoirs, oil and gas production by injection of liquid into wells, blasting during mining, etc. Less strong earthquakes occur when cave vaults 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. Elastic properties include the bulk modulus, which characterizes the resistance to compression without changing shape, and the shear modulus, which determines the resistance to shear forces. The speed of propagation of elastic waves increases in direct proportion square root values ​​of parameters of elasticity and density of the medium.

Longitudinal and transverse waves.

These waves appear first on seismograms. The first to be recorded are longitudinal waves, during the passage of which each particle of the medium is first compressed and then expanded again, 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 elastic modulus and rigidity of the rock. Near the earth's surface speed R-wave is 6 km/s, and at very great depths - approx. 13 km/s. The next to be recorded are transverse seismic waves, also called S-waves, or secondary waves. As they pass, each rock particle oscillates perpendicular to the direction of wave propagation. Their speed depends on the shear resistance of the rock and is approximately 7/12 of the speed of propagation R- waves

Surface waves

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

Amplitude and period

characterize the oscillatory movements of seismic waves. Amplitude is the amount by which the position of a soil particle changes during the passage of a wave compared to the previous state of rest. The period of oscillation is the period of time during which one complete oscillation of a particle occurs. Near the source of the earthquake, vibrations 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 oscillations 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. The amplitudes of oscillations 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 layers of rocks with different properties along their path, seismic waves are reflected or refracted, just as a ray of light is reflected from a mirror surface or refracted when passing from air to water. Any changes in the elastic characteristics or density of the material along the path of propagation of seismic waves cause them to be refracted, and with sudden changes in the properties of the medium, part of the wave energy is reflected ( cm. rice.).

Paths of seismic waves.

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

Seismic stations located far from the epicenter of an earthquake record not only direct waves R And S, but also waves of these types, already reflected once from the Earth’s surface - RR And SS(or PR 1 And S.R. 1), and sometimes - reflected twice - RRR And SSS(or PR 2 and S.R. 2). There are also reflected waves that travel one section of the path as R-wave, and the second, after reflection, - like S-wave. The resulting converted waves are designated as PS or SP. In seismograms of deep-focus earthquakes, other types of reflected waves are also observed, for example, waves that were 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 decrease sharply 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 is sharply deviated and a shadow zone appears on the Earth’s surface, within which only very weak waves are recorded 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 appear again, and their amplitude increases significantly due to the focusing influence of the core, where wave velocities are low. R-waves passing through the earth's core are designated RKR or Rў . The seismograms also clearly distinguish waves that travel like waves along the path from the source to the core S, then pass through the core as waves R, and upon output the waves are again converted to the type S. In the very center of the Earth, at a depth of more than 5,100 km, there is an inner core that is presumably in a solid state, but its nature is not yet entirely clear. Waves penetrating through this inner core are denoted as RKIKR or SKIKS(cm. rice. 1).

Registration of earthquakes.

The device that records seismic vibrations is called a seismograph, and the recording itself is called a seismogram. A seismograph consists of a pendulum suspended inside a housing by 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 moves to one side, so that the zero line of the recording on the paper looks like a spiral. Every minute, vertical lines are drawn on the graph - time stamps; very much used for this accurate watch, which are periodically checked against the exact time standard. To study nearby earthquakes, marking accuracy is required - down to a second or less.

In many seismographs, induction devices are used to convert a mechanical signal into an electrical one, in which, when the inert 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 drives a galvanometer connected to a mirror that casts a beam of light onto the light-sensitive paper of the recording device. In modern seismographs, vibrations are recorded in digital form using computers.

Earthquake Magnitude

usually determined on a scale based on seismograph recordings. This scale is known as the magnitude scale, or Richter scale (named after the American seismologist C. F. Richter, who proposed it in 1935). The magnitude of an earthquake is a dimensionless quantity 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 methods for determining the magnitudes of nearby, distant, shallow (shallow) and deep earthquakes. Magnitudes determined by different types waves differ 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 minor damage;

6 - moderate destruction;

8 1/2 - the strongest known earthquakes.

Earthquake intensity

are assessed in points during a survey of the area based on the magnitude of the destruction of ground structures or deformations of the earth's surface caused by them. To retrospectively assess the intensity of historical or more ancient earthquakes, some empirically obtained relationships are used. In the United States, intensity ratings are usually made using a modified 12-point Mercalli scale.

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

3 points. People feel it like vibration from a passing truck.

4 points. Dishes and window glass rattle, doors and walls creak.

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

6 points. It is felt by everyone. Minor damage.

8 points. Are falling chimneys, monuments, walls are collapsing. The water level in wells changes. Capital buildings are severely damaged.

10 points. Brick buildings are destroyed and frame structures. Rails become deformed and 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).

Intensity in points (expressed in whole numbers without fractions) is determined by examining the area in which the earthquake occurred, or by interviewing residents about their feelings in the absence of destruction, or by calculations using empirically obtained and accepted formulas for a given area. Among the first information about an earthquake that has occurred, it is its magnitude that becomes known, not its intensity. Magnitude is determined from seismograms even at large distances from the epicenter.

Consequences of earthquakes.

Strong earthquakes leave many traces, especially in the area of ​​the epicenter: the most common are landslides and slides 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 collapses often occur, and the thick layer of water-saturated alluvium in valleys is more easily deformed than hard rocks. On the surface of alluvium, subsidence basins are formed and 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 altitude position of individual points of the earth's surface along a fault line, as happened during the 1906 San Francisco earthquake. During the October 1915 earthquake in the Pleasant Valley in Nevada, a ledge 35 km long and up to 4.5 m high formed on the fault. During the May 1940 earthquake in the Imperial Valley in California, movements occurred along a 55-kilometer section of the fault, and horizontal displacements of up to 4 were observed .5 m. As a result of the Assam earthquake (India) in June 1897 in the epicentral region, the height of the area changed by no less than 3 m.

Significant surface deformations can be traced not only near faults and lead to a change in the direction of river flow, damming 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 boreholes are filled with mud, and the water level in them changes noticeably. During strong earthquakes, water, liquid mud or sand can be ejected from the ground in fountains.

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

During very strong shocks, structures built without taking into account seismic hazards can collapse and suffer severe damage. Typically, one- and two-story buildings do not collapse unless they have very heavy roofs. However, it happens that they move from the foundations and often their plaster cracks and falls off.

Differential movements can cause bridges to move from their supports and cause utilities and water pipes to break. During intense vibrations, pipes laid in the ground can “fold”, sticking into one another, or bend, coming to the surface, and railway rails become deformed. In earthquake-prone areas, structures must 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 earthquakes themselves is caused by fires that occur as a result of rupture of gas pipelines and power lines, overturning of stoves, stoves and other heating devices. Fighting fires is complicated by the fact that the water supply is damaged and the streets are impassable due to the resulting rubble.

Related phenomena.

Sometimes tremors are accompanied by a clearly audible low hum when the frequency of seismic vibrations lies in the range perceived by the human ear; sometimes such sounds are heard in the absence of tremors. They are quite common in some areas, although significant 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 yet. Tsunami ( big waves at sea) occur during rapid vertical deformations of the seabed during underwater earthquakes. Tsunamis propagate in the deep oceans at speeds of 400–800 km/h and can cause destruction on coastlines thousands of kilometers from the epicenter. On the shores close to the epicenter, these waves sometimes reach a height of 30 m.

During 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 mainshock and can recur over weeks or even years, becoming less and less frequent.

Geographical distribution of earthquakes.

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

The Pacific seismic zone runs along the west coast of South America. In Central America it splits into two branches, one following the island arc of the West Indies, and the other continuing north, expanding within the United States, to the western ranges 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 the islands of the southwestern part Pacific Ocean to New Zealand and Antarctica.

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

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

There are a number of areas where earthquakes occur quite frequently. These include East Africa, Indian Ocean and in North America valley of the river St. Lawrence and northeastern USA.

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 - west of the Carpathians. Deep-focus earthquakes are characteristic of the western edge of the 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 on the continental side.

Earthquake forecast.

To improve the accuracy of earthquake forecasts, it is necessary to better understand the mechanisms of stress accumulation in the earth's crust, creep and deformations on faults, to identify the relationships between 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, sharp changes in the properties of rocks (electrical, seismic, etc.), geochemical anomalies, water regime disturbances, atmospheric phenomena, as well as abnormal behavior of insects and other animals (biological precursors). This kind of research is carried out at special geodynamic testing sites (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 that allow them to quickly process data and determine the location of earthquake sources.