And because of what happens an earthquake?
- The main cause of the earthquake is the rapid displacement of the earth's crust as a whole at the time of plastic (fragile) deformation of elastically strained rocks in the earthquake focus. Most foci of earthquakes occur near the surface of the Earth. The displacement itself occurs under the action of elastic forces during the process of discharge-reducing elastic deformations in the volume of the entire section of the plate and shifting to the equilibrium position. The earthquake is a rapid (in geological scale) transition of the potential energy accumulated in elastically deformed (compressible, shifted or stretched) rocks of the earth's interior, into the energy of oscillations of these rocks (seismic waves), into the energy of the change in the structure of rocks in the source of the earthquake. This transition occurs when the rock strength limit is exceeded in the earthquake source.
The ultimate strength of the rocks of the earth's crust is exceeded as a result of the increase in the sum of the forces acting on it:
1. Forces of viscous friction of mantle convection currents about the earth's crust;
2. Archimedes force, acting on the light bark from the side of a heavier plastic mantle;
3. The lunar-solar tides;
4. Variable atmospheric pressure.
The same forces also lead to an increase in the potential energy of elastic deformation of rocks as a result of plate displacement under their action. The density of the potential energy of elastic deformations under the action of these forces increases almost the entire volume of the plate (differently at different points). At the moment of the earthquake, the potential energy of elastic deformation in the earthquake source quickly (almost instantly) decreases to the minimum residual (almost to zero). Whereas, in the vicinity of the source due to the shear during the earthquake of a plate as a whole, the elastic deformations somewhat increase. Therefore, there are often aftershocks in the vicinity of the main earthquake. In the same way, small pre-earthquake foreshocks can trigger a large in the vicinity of the original small earthquake. A large earthquake (with a large plate shift) can cause subsequent induced earthquakes even at the remote edges of the plate.
What causes an earthquake? Simply put: Because of the collision of two lithospheric plates.
- Earthquake # 769; notions tremors and fluctuations of the Earth's surface caused by natural causes (mainly tectonic processes) or artificial processes (explosions, filling of reservoirs, collapse of underground cavities of mine workings). Small shocks can also cause the rise of lava during volcanic eruptions.
Every year around a million earthquakes occur on the Earth, but most of them are so insignificant that they go unnoticed. Really strong earthquakes, capable of causing extensive destruction, happen on the planet about once every two weeks. Fortunately, most of them are at the bottom of the oceans, and therefore are not accompanied by catastrophic consequences (if an earthquake under the ocean manages without a tsunami).
Earthquakes are best known for the devastation they can produce. The destruction of buildings and structures is caused by soil vibrations or giant tidal waves (tsunamis) that occur during seismic displacements on the seabed.
- because of the motion of the earth's crust ...
- The origin of natural earthquakes easily superimposes the theory of the motion of Wegener's lithospheric plates. In summary, it looks like the crust is divided into giant plates. A bit like a cracked shell on a hard-boiled egg. Only lithospheric plates are much larger. However, they are not rigidly fixed, but constantly moving one relative to another. Movement can be in the horizontal and vertical direction. This is possible due to the fact that the blocks of the earth's crust are located on a plasma-like, relatively liquid layer of magma - the asthenosphere. And now the most important thing - any interactions of lithospheric plates are accompanied by processes of tectonism, volcanism and seismism. Especially strong shaking of the earth's crust occurs during rapid horizontal movements of oncoming and discontinuous.
In the twentieth century, new man-made earthquakes appeared. First, those that are caused by human industrial activity. For example, voids in mines or oil-bearing horizons, which reduce the established strength of existing rocks, which leads to the intensification of seismic processes. Secondly, the same underground voids some states use as a place of testing weapons, which causes earthquakes. Third, there are projects to create artificial oscillations of the earth's crust, which are regarded as tectonic weapons.
- the layers of the earth move)
- due to natural inconsistencies