Strike-slip faults, particularly continental transforms, can produce major earthquakes up to about magnitude 8.Megathrust earthquakes occur at subduction zones, where one tectonic plate is forced underneath another.Reverse faults (convergent boundary ) are associated with the most powerful earthquakes, megathrust earthquakes, including almost all of those of magnitude 8 or more.Slipping of land along the faultline along convergent, divergent and transform boundaries cause earthquakes.The fault ruptures along normal faults (divergent boundary) are shorter.The longest earthquake ruptures on strike-slip faults (transform fault) are about half to one third as long as the lengths along the thrust fault.The longest earthquake ruptures along thrust faults ( convergent boundary ) are approximately 1,000 km.The longer the length and the wider the width of the faulted area, the larger the resulting magnitude.Sudden slipping of rock formations along fault rupture in the earth’s crust happens due to the constant change in volume and density of rocks due to intense temperature and pressure in the earth’s interior.ĭeformation and Rupturing ( Steven Earle ).The immediate cause of most shallow earthquakes is the sudden release of stress along a fault rupture (crack) in the earth’s crust.Earthquake swarms can serve as markers for the location of the flowing magma throughout the volcanoes.Earthquakes associated with volcanic activity often occur in swarms.Such series of earthquakes are called earthquake swarms.Large numbers of small earthquakes may occur in a region for months without a major earthquake.A mild earthquake preceding the violent shaking movement of an earthquake is known as a foreshock.Usually, a major or even moderate earthquake of shallow focus is followed by many lesser-size earthquakes known as aftershocks.The focus of an Earthquake (Eround1, via Wikimedia Commons ) Epicentre (AnsateSam, via Wikimedia Commons ) Foreshocks and aftershocks A line connecting all points on the surface where the intensity is the same is called an isoseismic line.The point on the surface directly above the focus is called epicentre (first surface point to experience the earthquake waves).The point where the energy is released is called the focus or the hypocentre of an earthquake.A seismograph, or seismometer, is an instrument used to detect and record earthquakes.An earthquake is shaking or trembling of the earth’s surface, caused by the seismic waves or earthquake waves that are generated due to a sudden movement (sudden release of energy) in the earth’s crust (shallow-focus earthquakes) or upper mantle (some shallow-focus and all intermediate and deep-focus earthquakes).
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