HR: 1340h
AN: T43A-1380    [Abstracts]
TI: Crustal and Upper Mantle Structures of the High Himalaya, constrain from joint teleseismic and local earthquake tomographic inversion
AU: * Huang, G
EM: dino@geol.binghamton.edu
AF: Department of Geological Sciences, State University of New York at Binghamton, PO Box 6000, Binghamton, NY 13902-6000 United States
AU: Wu, F T
EM: wu@binghamton.edu
AF: Department of Geological Sciences, State University of New York at Binghamton, PO Box 6000, Binghamton, NY 13902-6000 United States
AU: Roecker, S W
EM: roecks@rpi.edu
AF: Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, 110 8th St., JSC 1W19, Troy, NY 12180 United States
AB: That the Himalaya mountain is the result of collision of the Indian and the Eurasian plates is well known. To understand the processes of mountain building basic images of the crust and upper mantle structures of Himalaya are necessary. The HIMNT project, mobilized in 2001-2002 to collect broadband seismic data for source and structures under Himalaya, consists of 28 stations bracketing Himalay in eastern Nepal and southern Tibet [Schutle-Pelkum et al., 2005]. In this study, a joint-tele/local-earthquake tomography was carried out to image the lithospheric structure underneath Himalay. A new algorithm developed by S. Roecker [Roecker et al., 2004] was employed. In addition to HIMNT data, data from LSA (GSN), 5 stations in Bhutan [Valesco] and INDEPTH-II stations in this study. For local earthquakes, arrivals were detected and associated by University of Colorado at Boulder [Monsalve et al. 2003]. Catalogs from PDE, NEIC and ISC provide the events that ranging in 30-90 degrees as teleseismic sources. Local events with three or more P and S arrivals, and teleseismic events with more than two P-arrivals selected. After testing with various node spacing, damping factor and model size, we adopted a model with its center at 28° E and 88° N and a dimension of 816km x 600km x 300km; the horizontal spacing of nodes is 8 km and vertical spacing of 4 km. To test the robustness of solutions we use 4 different initial models: IASPEI91 [Kennett et al., 1991], Nepalese model [Padney et al., 1995], INDEPTH-II receiver function results[Kind et al., 1996] and a model modified from the INDEPTH-II model by decreasing the Moho depth. The results show that crust under the Lesser Himalaya increase gradually toward the north from about 50 km; the High Himalaya is underlain by the transition to the southern Tibet crust of 70-80 km. A north-dipping high velocity anomaly down to a depth can be interpreted as an Indian subduction zone. The presence of crustal seismicity allows more detailed imaging there; mid-crustal low velocity and higher velocities under the high ranges are observed.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
SC: Tectonophysics [T]
MN: Fall Meeting 2005