Modern earthquakes. Earthquake. Other types of earthquakes

The earth's firmament has always been a symbol of security. And today a person who is afraid of flying on an airplane feels protected only when he feels a flat surface under his feet. Therefore, the worst thing is when the ground literally disappears from under your feet. Earthquakes, even the weakest ones, undermine the sense of security so much that many of the consequences are associated not with destruction, but with panic and are psychological rather than physical in nature. In addition, this is one of those disasters that humanity cannot prevent, and therefore many scientists are researching the causes of earthquakes, developing methods for recording tremors, forecasting and warning. The amount of knowledge already accumulated by humanity on this issue allows us to minimize losses in some cases. At the same time, examples of earthquakes recent years clearly indicate that there is still much to be learned and done.

Thus, the soil of the Pacific Ocean is submerged under the Mexican land mass. This always leads to serious upheavals that threaten the country. According to experts from the Central Institute of Meteorology and Geodynamics, the geological constellation of Tuesday's earthquake was such that Mexico was much more catastrophic.

Tsunami message in brief

It had a curve at the top, but luckily it lay deep. Thus, the hypocentrism of the earthquake was also very low. If it were much higher, there would be a lot more sacrifice. Ultimately, tensile stresses were observed on the surface of the knee.

The essence of the phenomenon

At the heart of every earthquake is a seismic wave that leads to it. It arises as a result of powerful processes of varying depth. Quite minor earthquakes occur due to surface drift, often along faults. The causes of earthquakes that are deeper in location often have devastating consequences. They flow in zones along the edges of shifting plates that are plunging into the mantle. The processes occurring here lead to the most noticeable consequences.

Fortunately, there are not many earthquakes in Mexico City, because the capital of Mexico sits on the bottom of a dry lake. The sediments of the former reservoir would have multiplied the impact of the earth's impacts. Lenhardt also noted that the ground strike since Tuesday had virtually nothing to do with the earthquake in the south of the country almost two weeks ago. Although it is approximately the same plate, the Chiapas-Oaxaca earthquake occurred at the lower edge of the plate.

Many buildings in Mexico City were damaged. Employees should be given the opportunity to care for their relatives after they suffered serious damage in nearby Puebla. So far, no structural damage has been identified, but inspections have continued. Some houses fell onto their foundations.

Earthquakes happen every day, but most of them go unnoticed by people. They are only recorded with special devices. In this case, the greatest force of tremors and maximum destruction occur in the zone of the epicenter, the place above the source that generated the seismic waves.

Scales

Today there are several ways to determine the strength of a phenomenon. They are based on concepts such as the intensity of the earthquake, its energy class and magnitude. The last of these is a quantity that characterizes the amount of energy released in the form of seismic waves. This method of measuring the strength of a phenomenon was proposed in 1935 by Richter and is therefore popularly called the Richter scale. It is still used today, but, contrary to popular belief, each earthquake is assigned not points, but a certain magnitude value.

Red Cross Disaster Relief

Red Cross emergency failure on high tranches. "There is a 72-hour window in which the chances are good for rescuing people from the wreckage," Walter Hajek, head of international cooperation at the Red Cross, said Wednesday. “The focus of the Red Cross is search and rescue,” Hayek said. “The Mexican Red Cross has more than 500 employees.” There were 17 search and rescue units in total. The outpatient clinic provides 90 ambulances for primary care of victims.

Earthquake scores, which are always given in the description of the consequences, are related to a different scale. It is based on a change in the amplitude of the wave, or the magnitude of the oscillations at the epicenter. The values on this scale also describe the intensity of earthquakes:

1-2 points: fairly weak tremors, recorded only by instruments;
3-4 points: noticeable in high-rise buildings, often noticeable by the swinging of a chandelier and the displacement of small objects, a person may feel dizzy;
5-7 points: tremors can be felt already on the ground, cracks may appear on the walls of buildings, plaster may fall off;
8 points: powerful tremors lead to deep cracks in the ground and noticeable damage to buildings;
9 points: walls of houses, often underground structures, are destroyed;
10-11 points: such an earthquake leads to collapses and landslides, collapse of buildings and bridges;
12 points: leads to the most catastrophic consequences, including severe changes in the landscape and even the direction of water movement in rivers.

Earthquake scores, which are given in various sources, are determined precisely on this scale.

Further treatment takes place in hospitals. However, some hospitals had to be evacuated. “The treatment continues on the streets,” Hayek said. Emergency shelters were created and people were provided with essentials. Another important activity of the Red Cross is family reunification. People are panicking. Families have been torn apart as a result of the chaos created and the Red Cross offers a phone number you can contact and that psychosocial support is important, the trauma is less severe.

Rescue services are searching for survivors in rural homes. The damage assessment has not yet been completed, but is being carried out in parallel with the high tranches. The airport and other infrastructure are damaged. According to Hajek, the airport should reopen from 00:00. The Mexican army also sent more than 1,000 soldiers to the affected area.

Classification

The ability to predict any disaster comes from a clear understanding of what causes it. The main causes of earthquakes can be divided into two large groups: natural and artificial. The former are associated with changes in the subsoil, as well as with the influence of certain cosmic processes, the latter are caused by human activity. The classification of earthquakes is based on the cause that caused it. Among natural ones, tectonic, landslide, volcanic and others are distinguished. Let's look at them in more detail.

Hayek said the large-scale exercise was completed just before the quake. Standards of building materials and building structures were improved, and a clear disaster relief plan was developed. Things have been very well developed over the last few years. We don't know the total damage yet, but basically everything is well prepared,” he said.

The ground in central Italy is not calming down after the weekend earthquake. Numerous aftershocks have been measured, one with a magnitude of 4, leaving tens of thousands of people homeless. The Italian government will hold a special session on relief measures in the afternoon.

Tectonic earthquakes

The crust of our planet is constantly in motion. This is what underlies most earthquakes. The tectonic plates that make up the crust move relative to each other, collide, diverge and converge. In places of faults, where plate boundaries pass and a compression or tension force occurs, tectonic stress accumulates. As it grows, sooner or later it leads to the destruction and displacement of rocks, as a result of which seismic waves are born.

The principle of earthquakes

The day after the earthquake in central Italy people don't rest. Many residents are unsure because there are always aftershocks - one of them reached 4.2 with great strength. At the same time, we are talking about assessing damage. Even in Rome, which is more than a hundred kilometers from the center of the earthquake, some churches were closed due to fears that falling components could harm visitors. At the same time, it becomes clear how devastating the damage has been caused to the regions of Umbria and Marche. Several villages are largely destroyed.

Vertical movements lead to the formation of failures or uplifting of rocks. Moreover, the displacement of the plates can be insignificant and amount to only a few centimeters, but the amount of energy released in this case is enough to cause serious destruction on the surface. Traces of such processes on earth are very noticeable. These could be, for example, displacements of one part of the field relative to another, deep cracks and failures.

Norcia, residents of the city of Norcia, with the epicenter of the earthquake, were no longer recognized, says local. “Norcia is no more, the main points of reference: the market square, the church, the Basilica of San Benedetto were beautiful, now the side walls have collapsed, the church tower has collapsed, the council tower is damaged.”

He goes into the winter - help becomes more difficult

It is not yet known how many people have lost their homes. More than a thousand men and women have received assistance, and thousands have been housed in hotels along the Adriatic coast and in Trasimeno, according to Civil Protection. Overall, however, many more people may be homeless, according to current estimates. Paolo Mancinelli of Italian disaster relief admits it is difficult to help all victims - especially as winter approaches.

Under the water column

The causes of earthquakes on the ocean floor are the same as on land - movements lithospheric plates. Their consequences for people are somewhat different. Very often, the displacement of oceanic plates causes a tsunami. Having originated above the epicenter, the wave gradually gains height and often reaches ten meters, and sometimes fifty, near the shore.

"As a result of the sunken temperatures, tents were no longer a solution, so we decided to house people in undamaged houses and hotels, but a particularly strong earthquake also caused destruction." Italian Prime Minister Matteo Renzi said that everything that was destroyed must be rebuilt, and he also declared an emergency aid. The vice-president of the Umbria region, Fabio Paparelli, urges not only to stay with the announcements.

“This is an exceptional situation, so we need special tools to deal with this exceptional situation.” Italian Prime Minister Matteo Renzi asked all Italians to stand together. But there are also ugly battles. He argued that the government ensured that initial reports that the earthquake had a magnitude of 7.1 were subsequently reduced to 6.5. The goal was not to fully compensate those concerned, writes Senator Enza Blundo. Other parties have accused her of using a natural disaster to conspire with conspiracy theories.

According to statistics, over 80% of tsunamis hit the shores of the Pacific Ocean. Today, there are many services in seismic zones working to predict the occurrence and spread of destructive waves and notifying the population of the danger. However, people still have little protection from such natural disasters. Examples of earthquakes and tsunamis at the beginning of our century are further confirmation of this.

Even the top of their own five-star movement distanced itself from the senator. Today, 149 people have already died. Most of them are in the state of Morelos, where 54 people have died, while in Puebla they add 26, the state of Mexico 9 and Mexico City confirm.

Sometimes earthquakes are caused by other factors

The US Geological Survey said it had a magnitude of 7.1 degrees and that the epicenter was five kilometers northeast of the city of Raboso, in the state of Puebla. An earthquake with a depth of 51 km was recorded shortly after 13 local time.

Volcanoes

When it comes to earthquakes, images of an eruption of hot magma that you once saw inevitably appear in your head. And this is not surprising: the two natural phenomena are interconnected. The cause of the earthquake may be volcanic activity. The contents of the fire mountains exert pressure on the surface of the earth. During the sometimes quite long period of preparation for an eruption, periodic and steam events occur that generate seismic waves. The pressure on the surface creates a so-called volcanic tremor (shaking). It consists of a series of small ground tremors.

First preliminary report of deaths. My hug of solidarity with the family. We care about families. “We begged them to leave their buildings to follow the testimony of the civil defense,” Interior Secretary Miguel Angel Osorio Chong pleaded through the same social network.

Collapsed in Mexico City with earthquakes. However, Mexicans across the city shared evidence, photographs and videos showing extensive damage to buildings, homes and businesses. Some images showed completely destroyed structures.

The cause of earthquakes is processes occurring in the bowels like active volcanoes, and went out. In the latter case, they are a sign that the frozen mountain of fire may yet awaken. Volcanic researchers often use microearthquakes to predict eruptions.

In many cases, it can be difficult to unambiguously classify an earthquake as tectonic or volcanic. The signs of the latter are the location of the epicenter in close proximity from the volcano and a relatively small magnitude.

Mexico earthquake: Enrique Peña Nieto activates action plan to help victims

There were people hugging and crying in the streets. Parts of the seismological service. Some of the videos that are circulating on the networks. The buildings began to move. The office said that until today "conflicts affected by two earthquakes" were detected, which were recorded at the epicenter in Puebla, and that it felt strongly in the Federal District.

Brief information about the strongest earthquake in the world

“The Argentine Ministry of Foreign Affairs reports that there are still no citizens affected by the two earthquakes that occurred on this day in Mexico,” the communiqué said. The official text added that “he is in constant contact with local authorities to verify the existence of Argentine survivors.”

Collapses

An earthquake can also be caused by rock collapse. Landslides and landslides in the mountains arise as a result of various processes in the bowels and natural phenomena, and human activity. Voids and caves in the ground can collapse and generate seismic waves. Rock falls are caused by insufficient drainage of water, which destroys seemingly solid structures. The collapse could also be caused by a tectonic earthquake. The collapse of an impressive mass causes minor seismic activity.

Other types of earthquakes

“The Ministry of Foreign Affairs wants to bring peace to all the families of Argentine citizens who are in Mexico,” the statement said. Earthquakes are tremors created along the earth's crust that generate surface vibration. They are the result of a release of energy caused by the internal tensions of the Earth, also called endogenous forces of landform transformation. Depending on their intensity, earthquakes can cause serious social disasters, causing death and destruction.

Such earthquakes are characterized by low strength. Typically, the volume of collapsed rock is not sufficient to cause significant fluctuations. However, sometimes earthquakes of this type lead to noticeable damage.

Classification by depth of occurrence

The main causes of earthquakes are associated, as already mentioned, with various processes in the bowels of the planet. One of the options for classifying such phenomena is based on the depth of their origin. Earthquakes are divided into three types:

What are the causes of earthquakes? The causes of earthquakes can be related to external events called athetonics and internal processes called tectonics. Lethargy processes are less frequent and cause small tremors with the falling or collapse of large blocks of stones, which creates a certain impact on the surface. Its coverage area is usually small.

Tectonic processes are predominant for the generation of earthquakes and can be divided into two types, depending on their origin: volcanism and tectonism. Earthquakes caused by volcanoes occur depending on the effects created by the pressure created by the magma inside the volcanic eruption. They also have a short duration and relatively short duration.

Surface - the source is located at a depth of no more than 100 km; approximately 51% of earthquakes belong to this type.
Intermediate - depth varies in the range from 100 to 300 km; the sources of 36% of earthquakes are located in this segment.
Deep-focus - below 300 km, this type accounts for about 13% of such disasters.

The most significant offshore earthquake of the third type occurred in Indonesia in 1996. Its source was located at a depth of over 600 km. This event allowed scientists to “enlighten” the planet’s interior to a considerable depth. In order to study the structure of the subsoil, almost all deep-focus earthquakes that are not dangerous to humans are used. Much of the data on the structure of the Earth was obtained from the study of the so-called Wadati-Benioff zone, which can be represented as a curved inclined line indicating the place where one tectonic plate sets under another.

On the other hand, tectonism is the movement carried out by tectonic plates and their effects. So when two plates move in opposite directions, moving towards each other, shock occurs and energy builds up over time. Over the years, this accumulated energy becomes so great that it destroys the resistance of the stones and causes internal placement followed by the release of energy that causes the most powerful earthquakes.

When earthquakes occur in oceanic zones, there are high chances of a tsunami occurring as internal seismic shocks form big waves. If these waves are near a coastal area, the damage can be incalculable. It is therefore common that in areas close to tectonic plates, in addition to mountains and volcanoes, there is a higher frequency of earthquakes. This is also due to the fact that geological faults and other large earthquakes are more common in these areas.

Anthropogenic factor

The nature of earthquakes has changed somewhat since the beginning of the development of human technical knowledge. In addition to natural causes that cause tremors and seismic waves, artificial ones also appeared. Man, mastering nature and its resources, as well as increasing technical power, through his activities can provoke a natural disaster. The causes of earthquakes are underground explosions, the creation of large reservoirs, and the production of large volumes of oil and gas, which result in voids underground.

One of the rather serious problems in this regard is earthquakes that occur due to the creation and filling of reservoirs. Huge volumes and masses of water exert pressure on the subsoil and lead to changes in the hydrostatic equilibrium in the rocks. Moreover, the higher the dam created, the greater the likelihood of the occurrence of so-called induced seismic activity.

In places where earthquakes occur due to natural causes, human activity often overlaps with tectonic processes and provokes natural disasters. Such data imposes a certain responsibility on companies involved in the development of oil and gas fields.

Consequences

Strong earthquakes cause great destruction over large areas. The catastrophic nature of the consequences decreases with distance from the epicenter. The most dangerous results of destruction are various Collapse or deformation of production facilities associated with hazardous chemicals, leading to their release into the environment. The same can be said about burial grounds and nuclear waste disposal sites. Seismic activity can cause contamination of vast areas.

In addition to numerous destructions in cities, earthquakes have consequences of a different nature. Seismic waves, as already noted, can cause landslides, mudflows, floods and tsunamis. Post-Earthquake Zones natural disaster often change beyond recognition. Deep cracks and failures, soil washout - these and other “transformations” of the landscape lead to significant environmental changes. They can lead to the death of the flora and fauna of the area. This is facilitated by various gases and metal compounds coming from deep faults, and simply by the destruction of entire sections of the habitat.

Strong and weak

The most impressive destruction remains after megaearthquakes. They are characterized by a magnitude greater than 8.5. Such disasters are fortunately extremely rare. As a result of similar earthquakes in the distant past, some lakes and river beds were formed. A picturesque example of the “activity” of a natural disaster is Lake Gek-Gol in Azerbaijan.

Weak earthquakes are a hidden threat. As a rule, it is very difficult to find out about the likelihood of their occurrence on the ground, while phenomena of more impressive magnitude always leave identification marks. Therefore, all industrial and residential facilities near seismically active zones are under threat. Such buildings include, for example, many nuclear power plants and power plants in the United States, as well as disposal sites for radioactive and toxic waste.

Earthquake areas

The uneven distribution of seismically dangerous zones on the world map is also associated with the peculiarities of the causes of natural disasters. IN Pacific Ocean located seismic belt, with which, one way or another, an impressive part of earthquakes is associated. It includes Indonesia, West Coast Central and South America, Japan, Iceland, Kamchatka, Hawaii, Philippines, Kuril Islands and Alaska. The second most active belt is the Eurasian one: the Pyrenees, the Caucasus, Tibet, the Apennines, the Himalayas, Altai, the Pamirs and the Balkans.

The earthquake map is full of other potential danger zones. All of them are associated with places of tectonic activity, where there is a high probability of collision of lithospheric plates, or with volcanoes.

The Russian earthquake map is also full of a sufficient number of potential and active sources. Most hazardous areas in this sense, this is Kamchatka, Eastern Siberia, Caucasus, Altai, Sakhalin and Kurile Islands. The most destructive earthquake in recent years in our country occurred on Sakhalin Island in 1995. Then the intensity of the natural disaster was almost eight points. The disaster led to the destruction of a large part of Neftegorsk.

The enormous danger of a natural disaster and the impossibility of preventing it forces scientists around the world to study earthquakes in detail: the causes and consequences, “identifying” signs and forecasting possibilities. It is interesting that technical progress, on the one hand, helps to more accurately predict threatening events, to detect the slightest changes in the internal processes of the Earth, and on the other hand, it also becomes a source of additional danger: accidents at hydroelectric and nuclear power plants, in mining sites, are added to surface faults. fires at work that are terrible in scale. The earthquake itself is a phenomenon as controversial as scientific and technological progress: it is destructive and dangerous, but it indicates that the planet is alive. According to scientists, a complete cessation of volcanic activity and earthquakes will mean the death of the planet in geological terms. The differentiation of the interior will be completed, the fuel that has been warming the interior of the Earth for several million years will run out. And it is still unclear whether there will be a place for people on the planet without 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 earth's crust at depths of no more than 16 km, but in some areas the depths of the foci 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 (catalogs) 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.

Richter G.F. Elementary seismology. M., 1963
Rikitake T. Prediction of earthquakes. M., 1975
Seismic scale and methods for measuring seismic activity. M., 1975

Find "EARTHQUAKES" on