HR: 1340h
AN: T13E-1621    [Abstracts]
TI: Variation of Rayleigh and Love Wave Fundamental Mode Group Velocity Dispersion Across India and Surrounding Regions
AU: * Acton, C E
EM: cea31@cam.ac.uk
AF: Bullard Laboratories, University of Cambridge, Madingley Road, Cambridge, CB3 0EZ, United Kingdom
AU: Priestley, K
EM: keith@esc.cam.ac.uk
AF: Bullard Laboratories, University of Cambridge, Madingley Road, Cambridge, CB3 0EZ, United Kingdom
AU: Mitra, S
EM: mitra@gg.iitkgp.ernet.in
AF: Department of Geology and Geophysics, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
AU: Gaur, V K
EM: gaur@cmmacs.ernet.in
AF: Indian Institute of Astrophysics Bangalore, Koramangala, Bangalore, 560034, India
AU: Rai, S S
AF: National Geophysical Research Institute, Uppal Road, Hyderabad, 500007, India
AB: We present group velocity dispersion results from a study of regional fundamental mode Rayleigh and Love waves propagating across India and surrounding regions. Data used in this study comes from broadband stations operated in India by us in addition to data from seismograms in the region whose data is archived at the IRIS Data Management Centre. The large amount of new and available data allows an improved path coverage and accordingly increased lateral resolution than in previous similar global and regional studies. 1D path- averaged dispersion measurements have been made using multiple filter analyis for source-receiver paths and are combined to produce tomographic group velocity maps for periods between 10 and 60 s. Preliminary Rayleigh wave group velocity maps have been produced using ~2500 paths and checkerboard tests indicate an average resolution of 5 degrees with substantially higher resolution achieved over the more densely sampled Himalayan regions. Short period velocity maps correlate well with surface geology resolving low velocity regions (2.0-2.4 km/s) corresponding to the Ganges and Brahmaputra river deltas, the Indo-Gangetic plains, the Katawaz Basin in Pakhistan, the Tarim Basin in China and the Turan Depression. The Tibetan Plateau is well defined as a high velocity region (2.9-3.2 km/s) at 10 s period, but for periods greater than 20 s it becomes a low velocity region which remains a distinct feature at 60 s and is consistent with the increased crustal thickness. The southern Indian shield is characterized by high crustal group velocities (3.0-3.4 km/s) and at short periods of 10 and 15 s it is possible to make some distinction between the Singhbhum, Dharwar and Aravali cratons. Initial Love wave group velocity maps from 500 dispersion measurements show similarly low velocities at short periods across regions with high sedimentation but higher velocities compared to Rayleigh waves across the Indian shield.
DE: 7205 Continental crust (1219)
DE: 7255 Surface waves and free oscillations
DE: 7270 Tomography (6982, 8180)
DE: 8100 TECTONOPHYSICS
DE: 9320 Asia
SC: Tectonophysics [T]
MN: 2007 Fall Meeting