HR: 0830h
AN: S31F-0827    [PDF]
TI: Could Scattering from an Accretionary Wedge Look Like a Slab?
AU: * Morozov, I B
EM: igor.morozov@usask.ca
AF: Univ. Saskatchewan, 114 Science Place, Saskatoon, SK S7N5E2 Canada
AB: The existing depth imaging approaches using multichannel teleseismic receiver functions (RF) assume predominance of mode-converted waves in the P-wave coda and treat the noise as primarily caused by the surface waves. However, high-resolution RF studies of the crust and uppermost mantle utilize short periods ($<$3 s) at which the lithosphere is highly conducive to numerous types of guided body waves, such as the multiple PmP, Pg, and Lg. Disregarding these modes could result in misinterpreting the signal-generated noise as dipping structures within the mantle. This is particularly important in the vicinities of linear crustal structures with strong sub-Moho expressions, such as subduction zones, that should create strong and coherent slab-like noise arrivals. A synthetic example of broadside scattering within the crust in the acquisition geometry of the 1993 Cascadia teleseismic experiment shows that scattering of the primary P-wave arrivals from an accretionary wedge could produce RF arrivals close to those observed in the records.Conventional interpretations of these arrivals based on assumptions of their mantle origin would lead to images of spurious slabs with a broad range of landward dips steeper than ~10 deg. Such features might be very difficult to distinguish from the true mantle structures. Raw amplitudes of the observed CASC93 arrivals decay with distance from the trench and support their scattered wave interpretation. Detailed pre-RF, pre-stack analysis is thus required for correct identification of the signal-generated noise and validation of the resulting depth images. Identification of coherent scattered events in RF records could also help locate major crustal structures, such as crustal sutures and subduction fault zones.
UR: http://w3.uwyo.edu/~seismic/ibm/ST.pdf
DE: 7200 SEISMOLOGY
DE: 7218 Lithosphere and upper mantle
DE: 7255 Surface waves and free oscillations
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting