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WITHDRAWN 3D Crust and Upper Mantle Velocity Structure of India and Surrounding Regions Using Rayleigh Wave Dispersion Analysis.

Description: 

WITHDRAWN We model the 3D shear-wave velocity structure of crust and upper mantle of India, Himalaya, Tibet and surrounding regions. This highly resolved lithospheric velocity structure upto a depth of 200 km provides detailed understanding and improved clarity on key evolution and deformation aspects. 2D group velocity tomography maps, resolvable laterally at 3°, are produced from 1D event-raypath dispersion curve between 10-120 s. They provide first order insights about the high velocity persistent in cratons of the Peninsular Indian shield, Eastern Himalayan syntaxis, Pamir, Hindukush and other regions representing high grade metamorphic rocks. Similarly, the Mahanadi and Godavari rift, Bay of Bengal basin, Himalayan foreland basin, Afghan Tadjik basin, Makran subduction zone, and Andaman islands represent the sediment-laden low group velocity structures. The shear-wave velocity (Vs) structure obtained by isotropic inversion is presented as depth sections and profiles to study its lateral variations across the entire region. Focal mechanisms of moderate-to-large earthquakes, Moho depth computed from Airy’s isostatic compensation, free-air gravity anomaly data from previous works are investigated in-tandem to discuss the Vs structure. Salient insights include flexural bending, underthrusting of Indian plate till Altyn-Tagh fault in western Tibet and till Jiasha suture in central and eastern Tibet, crustal thickness of each tectonic unit, and sediment thickness of major sedimentary basins. Very high velocity in upper mantle region of Indian cratons, Tibet and Hindukush-Pamir is speculated to be due to eclogite facies rocks unlike the Deccan Volcanic Province and eastern Dharwar craton where this high velocity layer is absent, possibly due to plume volcanism related thermal anomaly or metasomatism. The coherence between the convergence rate, deformation of topography, and the earthquake records discloses this regional scale velocity model as a baseline model that can be considered for disaster mitigation and research studies of local extent within the highly seismic Indo-Eurasia region.

Session: Crustal Imaging of High Seismic Hazard Regions

Type: Oral

Date: 4/20/2023

Presentation Time: 08:15 AM (local time)

Presenting Author: Siddharth Dey

Student Presenter: No

Invited Presentation: 

Authors