Study of the Indian Shield's Crustal and Lithospheric Structure Based on Joint Inversion of P-Receiver Functions and Rayleigh Wave Fundamental Mode Group Velocity Dispersion Data

Abstract

The CSIR-NGRI, Hyderabad, conducted seismic imaging of the crust and lithosphere structures of the Hyderabad region during the period 2020–21 by installing a 10-station broadband seismic network. The data from this network was used to perform a joint inversion of P-radial receiver functions (PRFs) and fundamental mode group velocity dispersion data of Rayleigh waves to estimate the crustal and lithospheric thicknesses beneath the eastern Dharwar Craton (EDC), India. Modelled Moho depths range from 35.5 to 37.6 km, with a mean of (36.7 ± 0.7) km, while modelled lithospheric thicknesses range from 134.0 to 154.0 km, with a mean of (139.6 ± 6.7) km. The modelled Moho depths reveal an NW–SE trending crustal thinning in the southwestern part of the Hyderabad region while the modelled lithospheric thicknesses show an NNE-SSW trending elongated region of down-warping below the central part of the study region, which is bounded by thinning of the lithosphere on both the eastern and western sides. A stacking of radial PRFs using the common conversion point (CCP) indicates three seismic discontinuities, namely the Moho discontinuity (an increase in positive PRF amplitude at 30.0–35.0 km depth), the Hales discontinuity (an increase in positive PRF amplitude at 90.0–115.0 km depth), and the Lithosphere-Asthenosphere Boundary (an increase in negative PRF amplitude at 140.0–160.0 km depth). Our modelling reveals a (36.7 ± 0.7) km thick Archean crust and a (139.6 ± 6.7) km thick lithosphere beneath the Hyderabad region, indicating the absence of a thick cratonic root beneath the EDC.