Earthquake - it tremors and vibrations of the earth's surface, which arise as a result of sudden shifts and breaks in the crust or upper mantle and transmitted over long distances in the form of elastic vibrations. The intensity of the earthquake is estimated at seismic scores. Known two major seismic belt of the Earth: the Pacific, which covers the ring of the Pacific Ocean, and the Mediterranean, which stretches across Eurasia south of the Iberian Peninsula in the west to the east of the Malay Archipelago. Within oceans significant seismic activity sredneokeanicheskie different ranges.
The most famous earthquake of Lisbon (1755), California (1906), Messinian (1908), Ashgabat (1948), Chilean (1960), Armenian (1988), Iran (1990 g .). Earthquakes are among the most destructive natural forces. The most powerful earthquake could be 10 thousand times more powerful than the atomic bomb dropped on Hiroshima in 1945. Strong earthquakes are catastrophic, second in the number of victims of typhoons and only ten times getting over the eruption of volcanoes. Material damage to a devastating earthquake could reach hundreds of millions of dollars. Number of weak earthquakes is much more than the strong. Thus, hundreds of thousands of earthquakes that occur each year on Earth, only a few disastrous.
They release about 1020 J of potential seismic energy, which represents only 0.01% of the heat energy of the Earth, which is radiated into space. Spatial distribution of earthquakes uneven. It is determined by the movement and interaction of lithospheric plates. The main seismic belt, which is allocated to 80% of the seismic energy is located in the Pacific Ocean near the trenches, where the promotion of young lithospheric plates beneath the continent. Energy release notes in the Eurasian fold belt in place of the collision of the Eurasian plate with Indian and African plates and areas sredneokeanicheskih ranges in terms of stretching the lithosphere. Cells earthquakes are located at depths of up to 700 km, but the majority (3/4) of the seismic energy released in cells that are found at a depth of 70 km. The position of the earthquake source and place the beginning of mass transfer (hypocenter) determined by recording the seismic waves that occur during earthquakes (from weak earthquakes cell hypocenter and the same).