HR: 13:55h
AN: S43C-02    [Abstracts]
TI: 3D Finite-Difference Modeling of Scattered Teleseismic Wavefields in a Subduction Zone
AU: * Morozov, I B
EM: igor.morozov@usask.ca
AF: University of Saskatchewan, 114 Science Place, Saskatoon, SK S7N5E2 Canada
AU: Zheng, H
EM: hs.zheng@usask.ca
AF: University of Saskatchewan, 114 Science Place, Saskatoon, SK S7N5E2 Canada
AB: For a teleseismic array targeting subducting crust in a zone of active subduction, scattering from the zone underlying the trench result in subhorizontally-propagating waves that could be difficult to distinguish from converted P- and S- wave backscattered from the surface. Because back-scattered modes often provide the most spectacular images of subducting slabs, it is important to understand their differences from the arrivals scattered from the trench zone. To investigate the detailed teleseismic wavefield in a subduction zone environment, we performed a full-waveform, 3-D visco-elastic finite-difference modeling of teleseismic wave propagation using a Beowulf cluster. The synthetics show strong scattering from the trench zone, dominated by the mantle and crustal P-waves propagating at 6.2-8.1.km/s and slower. These scattered waves occupy the same time and moveout intervals as the backscattered modes, and also have similar amplitudes. Although their amplitude decay characters are different, with the uncertainties in the velocity and density structure of the subduction zone, unambiguous distinguishing of these modes appears difficult. However, under minimal assumptions (in particular, without invoking slab dehydration), recent observations of receiver function amplitudes decreasing away from the trench favor the interpretation of trench-zone scattering.
DE: 7203 Body waves
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7290 Computational seismology
SC: Seismology [S]
MN: Fall Meeting 2005