Crust and Upper Mantle Velocity Structure Beneath the Chhotanagpur Plateau, India Using Waveform Modeling of Shear-Coupled Pl Waves and Other Phases
Description:
We perform waveform modeling of shear coupled-PL waveforms and S-to-P converted phases to estimate the shear and compressional wave velocity structure of the crust and uppermost mantle beneath the Chhotanagpur plateau and adjacent regions in India. We use broadband waveforms from teleseismic earthquakes with magnitudes between 5.5 and 8.0, focal depths ≥ 300 km, and epicentral distances between 300 and 700. Data are extracted from seismic stations located near the cities of Dhanbad (DHN), Bokaro (BOKR), Petarwar (PTWR), Khunti (KNTI), and Sahibganj (SBG). A modified form of the reflectivity method generates synthetic seismograms for the range of frequencies 0.002 Hz to 0.25 Hz, and the calculation of responses (essentially matrix multiplications) is distributed over 32 nodes of a High-Performance Computing (HPC) cluster, which reduces the computation time sufficiently to allow a global optimization to be performed via Very Fast Simulated Annealing.
The crustal thickness of the study area varies between ~40.5 km and ~45.6 km. The thickest and thinnest crust are found in the NE and SW of the study area, beneath seismic stations SBG and KNTI, respectively. The thick crust observed at station SBG may be due to flexure associated with the subduction of the Indian lithosphere beneath the Himalayan mountain range. Also, a low-velocity zone is observed in the upper crust at station SBG, which we attribute to sediment deposition of Ganga-Koshi formation. The higher Poisson’s ratios for seismic stations SBG (~0.29), DHN (~0.29), and BOKR (~0.30) indicate the possible presence of partial melt in the mafic lower crust. Statistical tools such as the Posterior Probability Density function and Parameter Correlation Matrices are used to estimate uncertainties associated with model parameters and to quantify trade-offs between model parameters in the modeling scheme.
Session: Earth’s Structure From the Crust to the Core [Poster]
Type: Poster
Date: 4/18/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Mukesh K. Das
Student Presenter: No
Invited Presentation:
Authors
Mukesh Das Presenting Author Corresponding Author mukesh_das@baylor.edu Baylor University |
Mohit Agrawal mohit@iitism.ac.in Indian Institute of Technology |
Anupam Patel apatel7716@sdsu.edu San Diego State University, University of California San Diego |
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Crust and Upper Mantle Velocity Structure Beneath the Chhotanagpur Plateau, India Using Waveform Modeling of Shear-Coupled Pl Waves and Other Phases
Category
Earth’s Structure From the Crust to the Core