Friday, December 18, 2009

We extraction of oil and water from under ground .Could this be the reasen for the frequent earthquakes?

An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's crust. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. The word earthquake is also widely used to indicate the source region itself. The Earth's lithosphere is a patch work of plates in slow but constant motion . Earthquakes occur where the stress resulting from the differential motion of these plates exceeds the strength of the crust. The highest stress (and possible weakest zones) are most often found at the boundaries of the tectonic plates and hence these locations are where the majority of earthquakes occur. Events located at plate boundaries are called interplate earthquakes; the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes (see, for example, New Madrid Seismic Zone). Earthquakes related to plate tectonics are called tectonic earthquakes.








Causes Of earthquakes:


Most earthquakes are powered by the release of the elastic strain that accumulates over time, typically, at the boundaries of the plates that make up the Earth's lithosphere via a process called Elastic-rebound theory. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core. Where these plates meet stress accumulates. Eventually when enough stress accumulates, the plates move, causing an earthquake. Deep focus earthquakes, at depths of hundreds of kilometres, are possibly generated as subducted lithospheric material catastrophically undergoes a phase transition since at the pressures and temperatures present at such depth elastic strain cannot be supported.





Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. A rare few earthquakes have been associated with the build-up of large masses of water behind dams, such as the Kariba Dam in Zambia, Africa, and with the injection or extraction of fluids into the Earth's crust (at certain geothermal power plants and at the Rocky Mountain Arsenal). Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. Finally, ground shaking can also result from the detonation of explosives.We extraction of oil and water from under ground .Could this be the reasen for the frequent earthquakes?
Yes, may be...

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