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Plate Tectonics has been phenomenal in explaining the kinematics of the mechanically strong outer layer of the Earth, called the lithosphere. However, the assumptions associated with the theory hold good primarily in oceanic regions. The simplicity of plate tectonics fail to apply in continental interiors, mainly in regions where two plates collide to form mountain belts. Deformation in such regions is diffused and widespread, not just being limited to the boundary. My research focuses in studying one of the most active continental deformation zones, the Himalaya and southern Tibet, formed due to the collision of the Indian and the Eurasian plate. I model the seismic velocity structure across this collision zone to show that the Indian plate underthrusts the Himalaya and a large portion of the Tibetan plateau.
From GPS geodesy we know that this collision is ongoing at a rate of ~50mm/yr (measured between Lhasa and Bangalore) and results in steady accumulation of elastic strain within the underthrust Indian plate and the mountain belt (The Himalaya). The sudden release of this accumulated strain energy causes earthquake, which occurs mostly on per-existing weak zones (called faults). We use waveform modeling to study the geometry of these faults and their associated motion, within and across the Himalaya. I use this understanding, combined with historical earthquake information and convergence rates, to show that two major seismic gaps exist within the Himalaya: a) in Kashmir and b) in Sikkim-Bhutan. These regions are sufficiently strained to produce mega-quakes of magnitude 8 or greater and pose a major seismic hazard in northern and eastern India. Finally I will express my opinion on how to deal with this impending danger.
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