HR: 11:30h
AN: S32A-05    [Abstracts]
TI: Free Surface Effect and Separation of Teleseismic Waves: Transmission & Reflection, Primary vs Multiple
AU: * Fan, C
EM: cfan@indiana.edu
AF: Indiana University, Bloomington, 1001 E. 10th Street, Bloomington, IN 47405 United States
AU: Pavlis, G L
EM: pavlis@indiana.edu
AF: Indiana University, Bloomington, 1001 E. 10th Street, Bloomington, IN 47405 United States
AU: Weglein, A B
EM: aweglein@central.uh.edu
AF: University of Houston, 617 Research and Science Building 1, Houston, TX 77204 United States
AU: Nita, B
EM: bnita@uh.edu
AF: University of Houston, 617 Research and Science Building 1, Houston, TX 77204 United States
AB: We examine the free surface effect on teleseismic waves recorded by passive seismic arrays on the surface, and develop a new way to separate the forward and free surface back scattered waves from the total teleseismic wavefield. Using one-way wavefield reciprocity the reflection responses (of seismic reflection geometry) can be reconstructed from the transmission responses (of teleseismic geometry). The free surface effect (back scattered waves) of the total teleseismic wavefield can be removed by using an inverse scattering series for the teleseismic transmission geometry. The removed free surface back scattered waves can be obtained by taking the difference between the teleseismic wavefield before and after free surface effect removal. This gives the equivalent response to that produced from reconstructed reflection waves using the reciprocity relation. Free surface multiples in the reflection waves are removed by the inverse scattering series of reflection geometry. This produces a direct separation of transmission and reflection waves of the total teleseismic wavefield without knowledge of earth models. Numerical tests of acoustic stratified layer lithospheric earth models demonstrate the effectiveness of the algorithm. Noise test shows that the algorithm can work with signal-to-noise ratio as low as 5. Reconstruction demands higher signal-to-noise ratio than the removal procedure. Test with elastic synthetic data indicates that the acoustic algorithm is still effective for small incidence angle that characterize teleseismic P waves at distance greater than 30 degrees. For shallow angles of incidence, either P and SV wave separation or an elastic algorithm will probably be necessary.
DE: 3260 Inverse theory
DE: 7200 SEISMOLOGY
DE: 7203 Body wave propagation
DE: 7205 Continental crust (1242)
DE: 7207 Core and mantle
SC: Seismology [S]
MN: 2005 Joint Assembly