terra firma at all times was a symbol of security.Today, a person who is afraid to fly on an airplane, feels safe, only to feel under your feet flat surface.Therefore, it is the most terrible thing that literally ground away from under their feet.Earthquakes, even the weakest, so strongly undermined the sense of security that many of the effects are not associated with the destruction and panic and have a psychological, not physical.In addition, it is one of those accidents, to prevent that humanity can not, but because many scientists investigate the causes of earthquakes, develop methods of fixation shocks, forecasting and warning.Already accumulated by mankind of knowledge on the subject to minimize the losses in some cases.At the same time examples of earthquakes of recent years clearly show that is still very much to learn and do.
essence of the phenomenon
At the heart of each earthquake is seismic wave that drives the Earth's crust.It arises as a result of powerful processes of different depths.Pretty minor earthquakes occur due to the drift of lithospheric plates on the surface, often along faults.The deeper reason for its location of earthquakes often have devastating consequences.They occur in areas along the edges of the shifting plates that sink into the mantle.The ongoing here processes lead to the most visible consequences.
Earthquakes happen every day, but most of them people do not notice.They only recorded by special instruments.The highest strength and maximum shock fracture occur in the epicenter zone, place over the fire, gave birth to seismic waves.
Scales
Today, there are several ways to determine the strength of the phenomenon.They are based on concepts such as the intensity of the earthquake, its magnitude and the energy class.The last of these is a value that indicates the amount of energy released in the form of seismic waves.This method of measuring the strength of the phenomenon was proposed in 1935 by Richter, and so people called the Richter scale.It is used today, but in it, contrary to popular belief, not every earthquake attributed points, and the particular value of magnitude.
points earthquakes, which are always given in the description of the effects are related to the other scale.It is based on the change in the amplitude of the wave, or oscillation magnitude at the epicenter.The values of this scale also describe the intensity of the earthquake:
- 1-2 points: rather weak tremors only registered devices;
- 3-4 points: noticeable in high-rise buildings, often noticeable in swinging chandeliers and displacement of small items, a person may feel dizzy;
- 5-7 points: You can feel the tremors already on the ground, perhaps the appearance of cracks on the walls of buildings, crumbling plaster;
- 8 points: the powerful tremors lead to the appearance of deep cracks in the earth, visible damage buildings;
- 9 points: break down the walls of houses, often underground structures;
- 10-11 points: an earthquake leads to avalanches 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 the rivers.
points earthquakes, which are in various sources are determined for this scale.
Classification
to predict any accident linked to a clear understanding of what causes it.The main causes of earthquakes can be divided into two groups: natural and artificial.The first related to changes in the interior, as well as the influence of some cosmic processes, the latter caused by human activity.Classification of earthquakes based on the reasons that caused it.Among the natural release tectonic, landslip, volcanic and others.Let us dwell on them in detail.
Tectonic earthquake
bark of our planet is constantly in motion.That is the basis of most earthquakes.The tectonic plates that make up the crust move relative to each other, collide, diverge and converge.In places fractures, where the boundaries of plates and a force of compression or tension, tectonic stress builds up.Growing, it will sooner or later leads to the destruction and displacement of rock, and the resulting seismic wave born.
vertical motions give rise to failures or lifting rocks.Moreover, the displacement of the plates may be small and be only a few centimeters, but the amount of energy released at the same time enough for serious damage on the surface.Traces of such processes on the ground is very noticeable.This may be, for example, offset one with respect to another part of the field, deep cracks and failures.
under a layer of water
causes of earthquakes on the ocean floor are the same as on land - motions of lithospheric plates.Several different implications for people.Very often offset oceanic plates causes a tsunami.Originating at the epicenter, the wave is gradually gaining altitude and at the shore often reaches ten meters, and sometimes fifty.
According to statistics, over 80% of the tsunami came down on the Pacific coast.Today there are many services in earthquake zones, workers on forecasting the emergence and spread of destructive waves and alerting the population about the dangers.However, people still little protected from such disasters.Examples of earthquakes and tsunamis beginning of this century - another proof.
Volcanoes
When it comes to earthquakes, inevitably arise in the mind and vision once red-hot magma eruption image.This is not surprising: two natural phenomena are linked.The cause of the earthquake could be volcanic activity.Content fiery mountain is putting pressure on the earth's surface.During the sometimes rather long period of preparation for the periodic eruptions of gas and vapor explosions, which generate seismic waves.Pressure on the surface creates a so-called volcanic tremor (shaking).It is a series of small shocks soil.
reason earthquakes are the processes occurring in the depths as the active volcanoes and extinct.In the latter case, they are a sign that the stood fiery mountain can still wake up.Researchers volcanic activity often use micro-earthquakes to predict eruptions.
In many cases, it is difficult to unambiguously attributed to tectonic earthquake or volcanic group.Signs of the latter is considered to be the location of the epicenter in the vicinity of the volcano, and a relatively small magnitude.
Collapses
cause of earthquakes can serve as the collapse of rocks.Avalanches and landslides in the mountains are caused by a variety of processes both in the interior and natural phenomena and human activities.Unleashes and can generate seismic waves of emptiness and caves in the ground.Rock falls contributes to the lack of water abstraction, which destroys the seemingly solid structure.The cause of the collapse can become a tectonic earthquake.The collapse of the impressive mass while causing minor seismic activity.
For these earthquakes are characterized by a small force.As a rule, the volume of collapsed rock is not enough to cause significant fluctuations.However, sometimes this type of earthquake lead to significant damage.
Classification depth of occurrence
main causes of earthquakes are linked, as already mentioned, with different processes in the bowels of the planet.One of the versions of the classification of such phenomena is based on the depth of their origin.Earthquakes are divided into three types:
- Surface - center is located at a depth of no more than 100 km of this type is about 51% of earthquakes.
- Intermediate - depth varies in the range from 100 to 300 km, this segment disposed pockets 36% earthquakes.
- Deep-- less than 300 km, the share of this type accounts for about 13% of such disasters.
most significant maritime third type earthquake occurred in Indonesia in 1996.Its center was located at a depth of more than 600 km.This event allowed the scientists to "enlighten" the bowels of the planet to a considerable depth.In order to study the structure of the subsoil are used in almost all deep-focus earthquakes are not dangerous to humans.Many data on the structure of the Earth have been obtained from the study of the so-called zone-Wadati Benioff, which can be represented by a curve sloping line represents the point of entering one tectonic plate under another.
Human activity
Nature earthquakes since the beginning of the development of technical knowledge of mankind has changed.In addition to natural causes tremors and seismic wave, appeared artificial.The man mastering nature and its resources, as well as increasing the technical power, their activities could trigger a disaster.The causes of earthquakes - it is underground explosions, the creation of large reservoirs, extraction of large volumes of oil and gas, resulting become void under the ground.
One fairly serious problems in this respect - the earthquake, arising from the creation and filling of the reservoirs.Huge in size and weight of the water column exert pressure on the subsoil and lead to changes in hydrostatic equilibrium in the rocks.The higher the dam is created, the more likely the emergence of so-called induced seismicity.
In areas where earthquakes occur due to natural causes, human activities are often superimposed on the tectonic processes and provokes natural disasters.Such data imposes certain responsibilities on companies developing oil and gas fields.
Consequences
Strong earthquakes cause great devastation over large areas.Catastrophic effects decreases with increasing distance from the epicenter.The most dangerous result of destruction - is a variety of man-made accidents.Collapse or deformation of industries involving hazardous chemicals, leading to their release into the environment.The same can be said about the cemeteries and places of burial of nuclear waste.Seismic activity is able to cause contamination of vast territories.
addition to numerous destructions in the cities, and the effects of the earthquake have different character.Seismic waves, as already noted, can cause landslides, mudflows, floods and tsunamis.Zone earthquake disaster often changed beyond recognition.Deep cracks and failures, soil erosion - these and other "transformation" of the landscape lead to significant environmental changes.They can lead to loss of flora and fauna of the area.This is facilitated by the various gases and metal compounds coming from deep faults, and just as much as the destruction of habitats sites.
strengths and weaknesses
most impressive destruction remain after megalozemletryaseny.They are characterized by the magnitude of more than 8.5.Such disasters, fortunately, extremely rare.As a result of these earthquakes in the past formed some lakes and rivers.The picturesque example of the "activity" of disaster - Lake Gek-Gol in Azerbaijan.
more modest magnitude earthquake, leading to serious accidents and deaths, called destructive, disastrous.However, the weak seismic activity can have an impressive impact.Such earthquakes causing cracking walls, swinging chandeliers, etc., and usually do not lead to catastrophic consequences.The greatest danger they are in the mountains, where they can cause serious collapses and landslides.Location foci of earthquakes near the hydroelectric or nuclear power can also cause man-made disaster.
Weak earthquake - a veiled threat.On the probability of their occurrence in the area, usually very difficult to find, while the more impressive for the magnitude of the phenomenon always leave markings.Therefore, under threat all industrial and residential development near the seismically active zones.These buildings include, for example, many nuclear power plants and the US, as well as the place of burial of radioactive and toxic waste.
earthquake area
With the features of the causes of the disaster and the related uneven distribution of seismically dangerous areas on the world map.In the Pacific seismic belt is located, which, one way or another, linked to the imposing of the earthquakes.It includes Indonesia, the west coast of Central and South America, Japan, Iceland, Kamchatka, Hawaii, the Philippines, the Kuril Islands and Alaska.The second most active zone - Eurasian Pyrenees, the Caucasus, Tibet, the Apennines, the Himalayas, Altai, Pamir and the Balkans.
map of earthquakes is complete and other areas of potential danger.All of them are associated with places of tectonic activity, where the probability of collision of lithospheric plates, or with volcanoes.
map of earthquakes in Russia is also full of a sufficient number of potential and existing lesions.The most dangerous zones in this sense - is Kamchatka, Eastern Siberia, the Caucasus, Altai, Sakhalin and the Kuril Islands.The most devastating in its consequences earthquake in recent years in our country was on the island of Sakhalin in 1995.Then the intensity of the disaster was almost eight points.The disaster led to the destruction of much of Neftegorsk.
huge natural disaster and the inability to prevent it makes scientists around the world to study in detail the earthquake: causes and consequences "identification" signs and forecasting capabilities.Interestingly, the technical progress on the one hand, makes it all the more accurately predict the terrible events that catch the slightest changes in the internal processes of the earth, and on the other - it is a source of additional danger: to faults surface added accident on hydro and nuclear power, oil spills in placesmining, horrible-scale fires in the workplace.The earthquake itself - the phenomenon is as ambiguous as the scientific and technological progress: it is destructive and dangerous, but suggests that the planet lives.According to scientists, the complete cessation of volcanic activity and earthquakes will mean the death of the planet in geological terms.Completed differentiation of mineral resources, runs out of fuel, warming inside the Earth for several million years.And while it is not clear whether there will be people on the planet without earthquakes.
