"Natural disaster - earthquake"Завантажити презентацію
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Earthquake an is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.
Depending on the cause and location of occurrence, earthquakes are divided into: - tectonic; - volcanic; avalanche; - moretrusy; - Man-made or anthropogenic.
Tectonic earthquakes occur due to the sudden removal of stress, such as the displacement along the fault in the earth's crust (recent studies show that the cause of deep earthquakes may be phase transitions in the mantle, which occur at certain temperatures and pressures).
Volcanic earthquakes result from sudden movements magmatic melt in the ground or in the result of the gap under the influence of these movements.
Man-made earthquakes may be caused by an underground nuclear test, filling reservoirs, oil and gas by pumping fluid into the borehole, blasting in mining and so on.
Cause of earthquakes The cause of the earthquake is the rapid displacement of crust as a whole at the time of plastic (brittle) deformation elastically strained rocks in the earthquake. Most earthquake foci occur near the surface of the Earth. This bias is caused by elastic forces during the discharge process - reducing the amount of elastic deformation in all areas of the plate and the shift to a state of equilibrium.
Characteristics of earthquake Earthquakes taking over large areas and are characterized by: the destruction of the buildings, which fall under the wreckage of people , the emergence of mass of fires and industrial accidents , flooding residential areas and entire regions; gassing during volcanic eruptions , lesions of the people and the destruction of buildings fragments of volcanic rocks , engage people and the occurrence of local fires in settlements from volcanic lava , failure of settlements in landslide earthquakes , destruction and flushing settlements tsunami waves , negative psychological effects.