HR: 09:25h
AN: T51F-06    [Abstracts]
TI: Crustal Structure Beneath The Bengal Basin From Joint Analysis Of Teleseismic Receiver Functions And Rayleigh Wave Dispersion
AU: * Nath, S K
EM: nath@gg.iitkgp.ernet.in
AF: Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, WB 721302 India
AU: Mitra, S
EM: mitra@gg.iitkgp.ernet.in
AF: Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, WB 721302 India
AU: Bhattacharya, S N
EM: snb@gg.iitkgp.ernet.in
AF: Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, WB 721302 India
AB: Teleseismic data recorded at the broadband seismological observatory of the Indian Institute of Technology Kharagpur (22.32deg N, 87.31deg E) were analysed to determine the seismic characteristics of the crust beneath the Bengal Basin. Receiver functions calculated from the teleseismic P-waveform for a range of backazimuths show little variation in the arrival times of the converted Ps phases, indicating a nearly one-dimensional structure beneath the station. Transforming the time domain receiver functions into the H-Vp/Vs domain for a stack of all receiver functions reveal a 38±2 km thick crust with a Vp/Vs value of 1.73±.01. Receiver functions stacked in narrow bins of backazimuth and great circle arc distance were inverted jointly, along with the group velocity dispersion data between 15-45s period from the region. 1D shear wave velocity structure of the Bengal Basin crust thus obtained beneath this station is the first such result for the western Bengal Basin. It consist of a 38-42km thick crust with a mid-crustal interface at 12-14kms, the average crustal shear wave velocity being 3.5 km/s. The top half kilometer has very low shear wave velocity and a large impedance contrast with the underlying layer. This represents the thin layer of unconsolidated sediments and weathered laterite in the near surface layer known from well data in the area and is consistent with the DSS result of a low velocity 250mts surface weathered layer resting on 1.5-3 km thick laterites that overlie the basement.
DE: 7205 Continental crust (1219)
SC: Tectonophysics [T]
MN: Fall Meeting 2005