Earthquakes are powerful manifestations of sudden releases of strain energy accumulated within the crust and propagated as seismic waves
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Natural
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| Earthquakes: Distribution and types | Knowing Earthquakes | Earthquakes in India | Earthquake Research in India | Earthquake studies in CESS |
| Global Mosaic of earthquakes |
| Earthquake distribution and tectonic plates |
| The interior of Earth |
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Earthquakes are powerful manifestations of sudden releases of strain energy accumulated within the crust and propagated as seismic waves
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Global Mosaic of earthquakes Earthquake do not occur uniformly throughout the world Activity mainly localised along plate boundaries-Midoceanic ridges, island arcs, orogenic belts etc. Few earthquakes occur within plates - Intraplate earthquakes
Boundaries
of major tectonic plates and distribution of
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Earthquake distribution and tectonic plates Earthquakes distribution explained in the theory of plate tectonics. The lithosphere consists of several large slabs of solid rocks called plates- Oceanic and Continental Plates move horizontally at a speed of a few centimetres per year. Motion of these plates is considered to be the basic cause of earthquakes. Plate boundaries are convergent, divergent or transform Majority of earthquakes occur along these boundaries- Interplate Earthquakes also occur away from the plate boundaries- Intraplate and SCR
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Many
processes including seismic activity are ultimately related to the Earth’s
internal structure |
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Interplate, intraplate and SCR earthquakes A larger number of earthquakes will occur along the edges of interacting plates - interplate earthquakes (Example: Seismicity associated with the Himalayan seismic belt) Earthquakes occurring within a continental or oceanic plate - intraplate earthquakes. Very rarely, earthquakes occur in the more stable and older part of the continents (referred to as cratons) - Stable Continental Region (SCR) earthquakes (Example: The 1993 event at Latur (Killari) The recurrence interval of interplate earthquakes is of the order of tens or hundreds of years, SCR earthquakes may recur only over tens or hundreds of thousands of years.Due to the lack of preparation to face an earthquake, damages due to such earthquakes are generally very high Identifying potential faults and assessing seismic hazard of SCR regions is a very challenging task.
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Among the natural calamities, earthquakes are the most destructive, in terms of loss of life and destruction of property Often, they occur without any warning, which make them the most feared and unpredictable natural phenomena On an average, two earthquakes of magnitude 8 are reported to occur globally every year Japan, the United States and China have experienced several damaging earthquakes in the past. These countries have also done some of the pioneering studies on earthquakes Many destructive earthquakes have occurred in India in the recent past, causing damages worth crores of rupees and claiming many thousands of human lives More than 650 earthquakes of magnitude >5.0 have been reported in India since 1890 Seismology, the science of understanding earthquakes, not only contributing to the understanding of the physics of the Earth’s interior, but also help in the seismic hazard assessment and mitigation As high quality seismic and geodetic data became available globally, earthquake processes are being better understood Studies in India have also taken a major leap. Broadband digital seismograph and geodetic network have now been established Data obtained through the seismological, geologic and geodetic observations can form the basis of a first order earthquake quantification in the country Because of its varied geological environments and trained man power, India can clearly take a lead role in earthquake research and contribute to the understanding of one of the most dreaded natural process
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