HR: 0800h
AN: S51A-0995    [Abstracts]
TI: Constraints on the Interpretation of S-to-P Receiver Functions
AU: * Wilson, D C
EM: davew@geo.utexas.edu
AF: University of Texas at Austin, Dept. of Geological Sciences 1 University Station C1100, Austin, TX 78712 United States
AU: Angus, D A
EM: angus@nmsu.edu
AF: New Mexico State University, Department of Physics, Las Cruces, NM 88003 United States
AU: NI, J F
EM: jni@nmsu.edu
AF: New Mexico State University, Department of Physics, Las Cruces, NM 88003 United States
AU: Grand, S P
EM: steveg@geo.utexas.edu
AF: University of Texas at Austin, Dept. of Geological Sciences 1 University Station C1100, Austin, TX 78712 United States
AB: We present results from a forward modeling study to asses the feasibility of using S-to-P converted phases to image the seismic discontinuity structure of the crust and upper mantle. We show that a significant level of interfering P-wave energy arriving before the direct S-wave arrival can overprint the S-to-P converted phases of interest produced by the direct S-wave arrival and may result in Sp receiver function phases that do not represent true Earth structure. The source of this P-wave energy is attributable to a number of phases, including those that have undergone multiple reflections off the Earth's surface. For deep focus earthquakes (300-600km deep), a significant amount of P-wave energy is observed from pPPP, pPPPP, and sPPPP phases, and arrives within the same time window as predicted for S-to-P converted phases from the direct S phase arrival. Furthermore, for earthquakes at all depths, interfering P-wave energy arrives within the same time window as predicted for S-to-P converted phases from the SKS phase arrival, limiting the usefulness of SKSp receiver functions for upper mantle imaging. To isolate true Sp receiver function phases from contamination due to other P-wave phases, we find it necessary to: 1) restrict the depth of earthquakes that we use to less than 300 km, and 2) restrict the earthquake epicentral distance range that we use to between 60-75 degrees and ensure that the observed phases have consistent moveout characteristics.
DE: 7203 Body waves
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: Fall Meeting 2005