HR: 1340h
AN: T43A-1378    [Abstracts]
TI: Constraining the Shear Wave Speed Structure Beneath NE India From the Eastern Bengal Basin to the Himalaya
AU: * Mitra, S
EM: mitra@gg.iitkgp.ernet.in
AF: Dept. of Geology and Geophysics, Indian Institute of Technology, Kharagpur, Kharagpur, 721302 India
AU: Hazarika, N
EM: nava@tezu.ernet.in
AF: Dept. of Physics, Tezpur University, Sonitpur, Napam, 784028 India
AU: Priestley, K
EM: keith@esc.cam.ac.uk
AF: Bullard Laboratories, Dept. of Earth Sciences, University of Cambridge, Madingley Rise, Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: Gaur, V K
EM: gaur@cmmacs.ernet.in
AF: Indian Institute of Astrophysics, Koramangala, Bangalore, 560 034 India
AB: We constrain the S-wave velocity structure of the crust and uppermost mantle of NE India using receiver functions from 10 broadband seismographs located along a ~400~km profile extending from the Bengal Basin to the Great Himalaya. Receiver functions from recordings at eight of these stations were previously used to examine the crustal structure but here we discuss analysis of an expanded dataset from the original eight stations plus data from two additional stations, one located on the Bengal Basin and the other located in the Great Himalaya. More importantly, we jointly invert the receiver function data with Rayleigh wave group velocity dispersion data for this region to better constrain the crustal structure. Analysis of data from the new southernmost site located at Agartala close to the Bay of Bengal shows a crustal thickness of 38-40~km with a 5~km thick very high velocity layer (S-wave velocity 4.9~km/s) immediately above the Moho, most likely indicating the existence of the oceanic crust south of the Bengal Basin hinge zone. The Moho beneath the Shillong Plateau is 34-36~km deep with a crustal structure typical of the Indian shield. To the north of the plateau the crust thickens to 42-44~km beneath the Brahmaputra Valley, to 48-50~km beneath the Lesser Himalaya, and 55-57~km below our second new site located at Tawang in the Great Himalaya. To the north of the Great Himalaya beneath the southern Tibetan Plateau, the Indian Moho continues to dip northward at ~6° reaching a depth of ~90~km beneath Lhasa.
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8103 Continental cratons
DE: 8108 Continental tectonics: compressional
DE: 8199 General or miscellaneous
SC: Tectonophysics [T]
MN: Fall Meeting 2005