Earthquakes in the Himalaya
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Earthquakes in the Himalaya Dibyashakti Panda1, Bhaskar Kundu1 and Vineet K. Gahalaut2 1 Department of Earth and Atmospheric Sciences, NIT Rourkela, Rourkela, India 2 CSIR-National Geophysical Research Institute, Hyderabad, India
Definition Earthquake: Sudden release of elastic strain energy along a fault. Himalayan arc: About 2500 km long mountain chain running from Afghanistan, Pakistan, India, Nepal, China, and Myanmar, formed due to collision/subduction of Indian and Eurasian plate. Main Himalayan thrust: The contact surface between the underthrusting Indian plate, and the overlying Himalayan wedge rocks.
Introduction With the advent of modern concept of plate tectonics “Himalaya-Tibetan orogenic system,” a classical subduction-collision plate boundary zone has attracted the attention of geoscientists globally, who have considered it as a “geodynamic black box.” Himalayan geodynamics, its genesis, earthquake occurrence process, and associated lithospheric deformation have largely been considered within the framework of the collision of the Indian and Eurasian plates at some period during the Eocene (~50 Ma), resulting in the subduction of the Indian plate below Tibet. This has resulted in intense crustal shortening and deformation, taken up by crustal stacking along a system of intracontinental thrusts
and internal deformation of adjacent Tibet and Indian plate (Murphy et al. 2009; Styron et al. 2011). In the present entry, we have tried to focus on Himalayan earthquakes, in view of advances in knowledge about the past ~1000 years of earthquakes’ occurrence processes, constrained by geodetic, historic, and seismological data, along the Himalayan arc in order to objectively assess seismic hazard of the region and adjoining Indo-Gangetic plains (~250 million hectares fertile plains), which is one of the most densely populated regions of the Southeast Asia accommodating ~40% of the India’s population. In addition to that, significant high relief of the Himalayan Mountains blocks the northward monsoonal winds from the Indian Ocean during June–September, resulting in intense orography-controlled precipitation, and associated seasonal water mass accumulation and mass redistribution by the Himalayan river system, which dominate the regional surface loading process along the arc. Further, this seasonal non-tectonic deformation also influences the tectonic deformation along the Himalayan convergent plate boundary, making Himalayan earthquake occurrence and associated deformation process much more complicated. Rather than repeating what has already been documented in a few excellent reviews (e.g., Bilham et al. 2017; Bilham 2019), we have attempted to add more information from the perspective of crustal deformation.
Geodynamic Models of Himalaya-Tibetan Orogenic System The Himalaya-Tibetan orogeny has always remained a key domain for scientific community in terms of geodynamic evolution and tectonic complexity. Deformation pattern along this subduction-collision plate boundary has been explored widely (Copley and McKenz
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