The causes of earthquakes and consequences. The nature of earthquakes

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 by feeling an even surface under his feet. This is the worst thing that happens when, literally, the soil leaves from under the feet. Earthquakes, even the weakest ones, undermine the sense of security so much that many consequences are associated not with destruction, but with panic and have a psychological rather than a physical nature. In addition, this is one of those catastrophes that humanity can not prevent, and so many scientists are exploring the causes of earthquakes, developing methods for fixing jolts, predicting and warning. Already accumulated by mankind the volume of knowledge on this issue allows to minimize losses in some cases. At the same time, examples of earthquakes in recent years clearly indicate that much remains to be learned and done.

The essence of the phenomenon

At the heart of each earthquake is a seismic wave, which sets in motion the earth's crust. It arises as a result of powerful processes of varying depth. Quite minor earthquakes occur because of the drift of lithospheric plates on the surface, often along faults. Deeper in their location, the causes of earthquakes often have devastating consequences. They flow in the zones along the edges of the shifting plates, which are immersed in the mantle. The processes occurring here lead to the most notable consequences.

Earthquakes happen every day, but most people do not notice. They are only fixed by special devices. At the same time, the greatest force of shocks and maximum destruction occur at the epicenter zone, above the source of the source that generated seismic waves.

Scales

Today, there are several ways to determine the strength of the phenomenon. They are based on such concepts 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. Such a method of measuring the strength of the phenomenon was proposed in 1935 by Richter and therefore popularly called the Richter scale. It is used today, however, contrary to popular belief, each earthquake is attributed not to points, but to a certain magnitude magnitude.

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

• 1-2 points: sufficiently weak shocks, recorded only by instruments;
• 3-4 points: perceptible in high-rise buildings, often noticeable by the rocking of the chandelier and the displacement of small objects, a person may feel dizzy;
• 5-7 points: the jolts can be felt already on the ground, there may be cracks on the walls of the buildings, shedding of plaster;
• 8 points: powerful tremors lead to the appearance of deep cracks in the ground, significant damage to buildings;
• 9 points: the walls of houses are destroyed, often underground structures;
• 10-11 points: such an earthquake leads to landslides and landslides, collapse of buildings and bridges;
• 12 points: leads to the most disastrous consequences, up to a strong change in the landscape and even the direction of movement of water in rivers.

Points of earthquakes, which are given in various sources, are determined precisely on this scale.

Classification

The ability to predict any catastrophe is associated with 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 bowels, 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 the natural isolate tectonic, avalanche, volcanic and others. Let us dwell on them in more detail.

Tectonic earthquakes

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

Vertical movements lead to the formation of dips or the raising of rocks. Moreover, the displacement of the plates may be insignificant and be only a few centimeters, but the amount of energy released while this is sufficient for serious damage to the surface. Traces of such processes on earth are very visible. This can be, for example, the displacement of one part of the field relative to the other, deep cracks and dips.

Under the water column

The reasons for the occurrence of earthquakes on the ocean floor are the same as those on land - movements of lithospheric plates. Their consequences for people are somewhat different. Very often displacement of oceanic plates causes a tsunami. Originating over the epicenter, the wave gradually gains height and off the coast often reaches ten meters, and sometimes fifty.

According to statistics, over 80% of tsunamis are falling on the shores of the Pacific Ocean. Today, there are many services in the seismic zones working to predict the occurrence and spread of destructive waves and alert the public about the danger. However, the person is still little protected from such natural disasters. Examples of earthquakes and tsunamis of the beginning of this century are another proof of this.

Volcanoes

When it comes to earthquakes, willy-nilly in the head there are also images of the eruption of red-hot magma that were once seen. And this is not surprising: two natural phenomena are related. The cause of the earthquake may be volcanic activity. The contents of the fiery mountains put pressure on the surface of the earth. During a sufficiently long period of preparation for the eruption, periodic explosions of gas and vapor occur, which generate seismic waves. Pressure on the surface creates the so-called volcanic tremor (trembling). It is a series of small earthquakes.

The cause of earthquakes are processes occurring in the depths of both active volcanoes and extinct ones. In the latter case, they are a sign that the frozen fiery mountain can still wake up. Researchers of volcanic activity often use micro-earthquakes to predict eruptions.

In many cases, it is difficult to unambiguously refer the earthquake to a tectonic or volcanic group. Signs of the latter is the location of the epicenter in the immediate vicinity of the volcano and a relatively small magnitude.

The collapses

The cause of the earthquake can serve as a collapse of rocks. Collapses and landslides in the mountains arise as a result of both the various processes in the depths and natural phenomena, and human activity. Fall and generate seismic waves can emptiness and caves in the earth. The collapse of rocks is facilitated by insufficient water drainage, which destroys seemingly solid structures. The cause of the collapse may be a tectonic earthquake. The collapse of an impressive mass causes minor seismic activity.

For such earthquakes, a small force is characteristic. As a rule, the volume of the collapsed rock is not enough to cause significant fluctuations. Nevertheless, sometimes earthquakes of this type lead to appreciable destruction.

Classification by depth of occurrence

The main causes of earthquakes are related, 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:

• Surface - the focus is located at a depth of not more than 100 km, this type refers to about 51% of earthquakes.
• Intermediate - the depth varies in the range from 100 to 300 km, on this segment 36% of earthquakes are located.
• Deep-focus - below 300 km, this type accounts for about 13% of similar catastrophes.

The most significant marine earthquake of the third type occurred in Indonesia in 1996. Its focus was located at a depth of more than 600 km. This event allowed scientists to "enlighten" the depths of the planet to a significant depth. For the purpose of investigating the structure of the subsoil, almost all deep-focus earthquakes that are harmless to humans are used. Many data on the structure of the Earth were obtained from a study of the so-called Vadati-Beniof zone, which can be represented as a curve of an inclined line indicating the place where one tectonic plate approaches another.

Anthropogenic factor

The nature of earthquakes since the beginning of the development of the technical knowledge of mankind has changed somewhat. In addition to natural causes that cause earthquakes and seismic waves, artificial ones also appeared. Man, mastering nature and its resources, as well as building up its technical power, can provoke a natural disaster by its activities . The causes of earthquakes are underground explosions, the creation of large reservoirs, the extraction of a large volume of oil and gas, resulting in the emptiness of the ground.

One of the quite serious problems in this regard is the earthquakes that arise from the creation and filling of reservoirs. Huge in volume and mass of the water column exert pressure on the interior and lead to a change in hydrostatic equilibrium in the rocks. In this case, the higher the dam created, the greater the probability of occurrence of so-called induced seismic activity.

In places where earthquakes occur for natural reasons, human activities often overlap tectonic processes and provoke the occurrence of natural disasters. Such data imposes a certain responsibility on companies engaged in the development of oil and gas fields.

Effects

Strong earthquakes lead to large disruptions in vast areas. The catastrophic consequences diminish with distance from the epicenter. The most dangerous results of destruction are various man-made accidents. The collapse or deformation of industries associated with hazardous chemicals leads to their release into the environment. The same can be said about the burial grounds and burial sites of nuclear waste. Seismic activity can cause contamination of vast areas.

In addition to the numerous destruction in cities, earthquakes have consequences of a different nature. Seismic waves, as already noted, can cause landslides, mudflows, floods and tsunamis. Earthquake zones after a natural disaster often change beyond recognition. Deep cracks and dips, flushing of the ground - these and other "transformations" of the landscape lead to significant ecological 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 the destruction of entire areas of the habitat.

Strong and weak

The most impressive destruction remains after megalo earthquakes. They are characterized by a magnitude higher than 8.5. Such disasters, fortunately, are extremely rare. As a result of similar earthquakes in the distant past, some lakes and riverbeds were formed. A picturesque example of the "activity" of the disaster is Lake Huck-Gol in Azerbaijan.

More moderate in magnitude earthquakes, leading to serious accidents and loss of life, are called destructive and catastrophic. However, weak seismic activity can have impressive consequences. Such earthquakes cause cracking of walls, shaking of chandeliers and others and, as a rule, do not lead to catastrophic consequences. The greatest danger they represent in the mountains, where they can cause serious landslides and landslides. The location of the foci of such earthquakes near the hydropower plant or nuclear power plant can also cause anthropogenic catastrophe.

Weak earthquakes are a hidden threat. The probability of their occurrence on the ground, as a rule, is very difficult to learn, while the more impressive phenomena always leave marking marks. Therefore, all industrial and residential facilities near the seismically active zones are under threat. Such structures include, for example, many nuclear power plants and US power plants, as well as places for the disposal of radioactive and toxic waste.

Areas of earthquakes

With the peculiarities of the reasons for the occurrence of a natural disaster, uneven distribution of seismically dangerous zones on the world map is also associated. In the Pacific there is a seismic belt, with which, in one way or another, an impressive part of the earthquakes. It includes Indonesia, the west coast of Central and South America, Japan, Iceland, Kamchatka, Hawaii, the Philippines, the Kuriles and Alaska. The second belt in terms of activity is Euro-Asian: the Pyrenees, the Caucasus, Tibet, the Apennines, the Himalayas, the Altai, the Pamirs and the Balkans.

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

The earthquake map of Russia is also full of a sufficient number of potential and active centers. The most dangerous zones in this sense are Kamchatka, Eastern Siberia, the Caucasus, Altai, Sakhalin and the Kuril Islands. The most devastating earthquake of recent years in our country occurred on the island of Sakhalin in 1995. Then the intensity of the disaster amounted to almost eight points. The catastrophe led to the destruction of most of Neftegorsk.

The great danger of a natural disaster and the impossibility of preventing it causes scientists from all over the world to study in detail earthquakes: the causes of occurrence and consequences, the "recognition" signs and the possibilities of forecasting. It is interesting that technological progress, on the one hand, helps to more accurately predict terrible events, to catch 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 power stations and nuclear power stations , oil spills in places are added to the faults of the surface Production, horrible fires in production. The earthquake itself is as ambiguous as scientific and technological progress: it is destructive and dangerous, but it shows that the planet lives. According to scientists, the complete cessation of volcanic activity and earthquakes will mean the death of the planet in a geological plan. The differentiation of subsurface will be completed, the fuel will be over, warming up the interior of the Earth for several million years. And it is not clear yet, whether there will be a place for people on the planet without earthquakes.