A Seismic Investigation of Lithospheric Seismic Structure Beneath the Shillong Plateau and Adjoining Regions in N-E India by Jointly Fitting of Receiver Functions and Dispersion Curves
Description:
The northeastern Indian region is characterized by a complex lithospheric structure that developed as a result of collision between the Indian and Eurasian tectonic plates, in the north, and to subduction beneath the Burmese arc, in the east. To constrain this structure we jointly model Ps receiver functions, Sp receiver functions, and Rayleigh wave group velocity dispersion curves by performing a broad search for acceptable models via Very Fast Simulated Annealing (VFSA). Seismic Vp and Vs profiles are estimated from teleseismic earthquake data recorded by nine broadband seismic stations. We identify three distinct tectonic domains: the Shillong plateau, Brahmaputra valley, and the Indo-Burma convergence zone (IBCZ). Our results reveal that the region’s thinnest crust lies beneath the Shillong plateau, where crustal thickness increases slightly from the plateau’s eastern edge to its center and reaches a maximum at the western edge of the plateau. Crustal Vp/Vs ratios range between 1.69-1.75 for the Shillong plateau, consistent with a felsic composition. Deeper Moho depths beneath the Brahmaputra valley, adjacent to the northern front of the Shillong plateau, may be due to the flexure of the Indian lithosphere subducting beneath Asia. Low-velocity zones are indicated at ~5-10 km depth beneath the Brahmaputra valley, which may have been developed by NE-SW trending compressional stresses from the collision at the Himalayan arc and subduction at the Burmese arc. The crust is thickest in Kohima, beneath the Naga thrust in the IBCZ, where a high-velocity zone is observed for both Vp and Vs at a depth of 25-40 km. This anomaly may be associated with a high-velocity slab, trending N-NE to S-SW, comprising the subducting Indian lithosphere in the IBCZ. Uncertainties of our Vp and Vs models for all the nine broadband stations are estimated with two statistical tools: Posterior Probability Density Functions and Parameter Correlation Matrices.
Session: Earth’s Structure From the Crust to the Core
Type: Oral
Date: 4/18/2023
Presentation Time: 02:15 PM (local time)
Presenting Author: Mukesh K. Das
Student Presenter: No
Invited Presentation:
Authors
Mohit Agrawal mohit@iitism.ac.in Indian Institute of Technology |
Mukesh Das Presenting Author Corresponding Author mukesh_das@baylor.edu Baylor University |
Sachin Kumar sachinism15@gmail.com Louisiana State University |
Jay Pulliam jay_pulliam@baylor.edu Baylor University |
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A Seismic Investigation of Lithospheric Seismic Structure Beneath the Shillong Plateau and Adjoining Regions in N-E India by Jointly Fitting of Receiver Functions and Dispersion Curves
Category
Earth’s Structure From the Crust to the Core