Crustal Structure beneathWestern Bengal Basin using Receiver Function Analysis

Bohidar, Soumya (2018) Crustal Structure beneathWestern Bengal Basin using Receiver Function Analysis. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Soumya Bohidar (13MS146)) 13MS146.pdf - Submitted Version Restricted to Repository staff only Download (6MB)

Abstract

We study the crustal structure beneath the western Bengal basin by analyzing the teleseismic data recorded at the station Bakreshwar (BAKR) and Mohanpur (MOHN). Receiver functions are calculated from the teleseismic P waveform and then stacked in narrow bins of back-azimuth and epicentral distance in order to find the subsurface lateral variation in the crustal structure of this region. Receiver functions are transformed into the H -Vp /Vs domain and forward modeled for each cluster. Then receiver functions are jointly inverted with Rayleigh wave group velocity dispersion data for discrete time periods from the range of 15-60 s using an initial model obtained from the forward modelling in order to find the crustal shear wave velocity structure. These velocity models are then compared with previously obtained models from central deep basin to understand the transition from continental crust to the thinned transitional crust across the Eocene hinge zone. There are three different velocity structures observed beneath Bengal basin. In the stable shelf region which lies in the western part of the basin, the crustal structure is broadly similar to Indian continental crust with average shear wave velocityof 3.8 km s⁻¹ and average Moho depth of 38 km. As we move east, along the Hinge zone, the sediment layer thickness increases to 10 km and the basement layer thickness is ~30 km with shear wave velocity of 4.0 km s⁻¹. The central deep basin has a thinned transitional crust of 20 km thickness with shear wave velocity 4.2 km s⁻¹ which is overlain by a 20 km thick sediment layer. This crustal structure in the deep basin is transitional both in velocity and thickness between typical continental and oceanic crust.

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