HR: 1340h
AN: T13E-1639    [Abstracts]
TI: Crustal Structure Of The Himalayan Foreland Basin Inferred From Surface Wave Group Velocity Analysis
AU: * Mitra, S
EM: mitra@gg.iitkgp.ernet.in
AF: Dept. Geology and Geophysics, Indian Institute of Technology, Kharagpur, WB 721302, India
AU: Rai, S S
EM: raiss@rediffmail.com
AF: Seismic Tomography, National Geophysical Research Institute, Uppal Road, Hyderabad, AP 500007, India
AU: Bhattacharya, S N
EM: snb@gg.iitkgp.ernet.in
AF: Dept. Geology and Geophysics, Indian Institute of Technology, Kharagpur, WB 721302, India
AB: The Himalayan foreland basin is one of the largest and most dynamic terrestrial basins on the earth's surface. It stretches between the syntaxial belt of NW and NE Himalaya and arc southward into the Arabian Sea in the west and the Bay of Bengal in the east. The foreland can be broadly sub- divided into the Gangetic and the Indus basins. The Gangetic foreland basin fronts the eastern and central Himalaya, while the Indus foreland is situated to the south of the NW Himalaya forming the western edge of the Indian subcontinent. The Aravalli craton divides the Himalayan foreland with the Gangetic basin to its east and the Indus basin to the west. We study the crustal fabric of the two basins through surface wave group velocity modeling. We use several local and regional earthquakes from Himalaya and Pakistan recorded on the broadband seismographs located on the southern edge of the Ganga basin. Most of the data set provides pure path analysis of the crustal structure of these basins. Inversion of fundamental and first higher mode Rayleigh wave group velocity dispersion for the Ganga Basin reveal a ~5 km thick sedimentary layer with V_s 2.75 km/s followed by a two layer crust with average V_s of 3.6 km/s and an S_n velocity of 4.2 km/s. A comparison with the shear wave velocity models of the Indus basin show that the Gangetic basin is underlain by felsic crust similar to those of Bundelkhand craton, north India, while the Indus basin has a more mafic, higher velocity crust. The crustal thickness beneath both basins is similar (~40 km), but the S_n velocity beneath the Indus basin (~4.5 km/s) is much higher than that of the Ganga basin.
DE: 7200 SEISMOLOGY
DE: 7205 Continental crust (1219)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting