HR: 1340h
AN: T43A-1377    [Abstracts]
TI: Crustal Structure Beneath the Darjeeling-Sikkim Himalaya from Teleseismic Receiver Functions
AU: Acton, C
EM: charlotte.acton@cantab.net
AF: Bullard Laboratories, Dept. of Earth Sciences, University of Cambridge, Madingley Rise, Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: Mitra, S
EM: mitra@gg.iitkgp.ernet.in
AF: Dept. of Geology and Geophysics, Kharagpur, Kharagpur, 721302 India
AU: Mukul, M
EM: mlym@cmmacs.ernet.in
AF: Centre for Mathematical Modelling and Computer Simulation, Belaur Campus, Bangalore, 560 037 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: Nath, S K
EM: nath@gg.iitkgp.ernet.in
AF: Dept. of Geology and Geophysics, Kharagpur, Kharagpur, 721302 India
AB: The Darjeeling-Sikkim Himalaya lying between Nepal and Bhutan share the broad thrust geometries of the Himalayan belt, but differ from elsewhere along the arc in that the surface traces of the Main Central and the Main Boundary thrusts in the frontal part of the mountain belt are exposed within just a few kilometers of each other and the intervening region is occupied by several imbricate thrusts active in the Quaternary. These and other differences, notably the southward intrusion of the Tibetan plateau along the Yadong-Gulu rift zone between Sikkim and Bhutan, suggest possible differences in the crustal structure beneath this part of the range. We analyzed teleseismic receiver functions from 6 broadband seismographs operated in the area to resolve the crustal structure in the region and compare it with those from two nearly parallel sites in Arunachal Himalaya ~400 km further east. Moho converted Ps phases in the receiver functions from Darjeeling and a site ~50 km to the east, require the Moho to be at a depth of ~48 km, nearly equal to the Moho depth at Bomdila in a similar setting but ~400 km to the east of Darjeeling. Furthermore, consistent with this observation, at a third site about 50 km north of Darjeeling the Moho is at a depth of ~58 km, similar to the Moho depth beneath Tawang, situated at a similar position in the range but 400 km to the east. These observations testify to a coherent geometry of the lower part of the underthrusting Indian plate in the eastern Himalayas.
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