HR: 1340h
AN: T43A-1383    [Abstracts]
TI: A 3-Dimensional Image of the Moho beneath the Shillong Plateau
AU: Hazarika, N
EM: nava@tezu.ernet.in
AF: Dept. of Physics,Tezpur University, Sonitpur, Napam, 784028 India
AU: * Mitra, S
EM: mitra@gg.iitkgp.ernet.i
AF: Dept. of Geology and Geophysics, Indian Institute of Technology -, Kharagpur, Kharagpur, 721302 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: Using receiver function analysis along a NS traverse across the ~1 km high uncompensated Shillong Plateau, Mitra et al. (2005) showed that the crust beneath Shillong was thinner than under the basement outcrops in the Brahmaputra Valley to the north and the Bengal Basin to the south, requiring that the plateau be supported by dynamics stresses on two E-W trending reverse faults. To constrain this hypothesis further, we examine receiver functions from broadband seismic data from previous sites and from 4 new sites distributed across the plateau and a fifth site in Mikir Hills to determine a 3D image of the crust beneath the plateau and its northern extensions exposed as a spur of basement outcrops in the Brahmaputra Valley. The Moho Ps converted phases for sites on the Shillong Plateau yield a crustal thickness of 34-36 km, with a slight thickening to 38-40 km at the NW edge of the plateau, and substantial thickening to 42-44 km below the Brahmaputra Valley. The site in the eastern Mikir Hills close to the Brahmaputra Valley and NE of the seismically active Kopili lineament shows a crustal thickness of 35 km, characteristic of the plateau suggesting similar fault generated uplift. Combining the seismic observations allows us to construct a 3D map of the Moho beneath this region. This, however, raises new questions about the relationship of the northern reverse fault that uplifts the Shillong Plateau and other faults that may be responsible for having similarly uplifted the less elevated Mikir Hills.
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8103 Continental cratons
DE: 8106 Continental margins: transform
DE: 8199 General or miscellaneous
SC: Tectonophysics [T]
MN: Fall Meeting 2005