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Correlation Migration Using Gaussian Beams of Scattered Teleseismic Body Waves

¹ Department of Earth and Atmospheric Sciences
550 Stadium Mall Drive
Purdue University
West Lafayette, Indiana 47906
 (R.L.N., S.D.)

² Geology and Geophysics Department
University of Utah
Salt Lake City, Utah 84112
 (G.T.S., J.M.S.)

View larger version (23K): [in this window] [in a new window]   Figure 1. (A) Frame-based Gaussian beam decomposition. Initial wave fields are decomposed into Gaussian windowed beam components that are then launched at different angles into the medium. (B) Example of the backpropagation of a single Gaussian beam with a low-frequency initial beam width of 30 km for a pPp phase for the model shown in Figure 2.

View larger version (15K): [in this window] [in a new window]   Figure 2. A collisional zone model.

View larger version (58K): [in this window] [in a new window]   Figure 3. Ray-Born synthetics for the collisional zone model in Figure 1. The source P wave is incident at 20° from the vertical. The scattering is incorporated by using point scatterers embedded in a two-layer velocity structure. The modeled phases include the direct ps, and the surface-reflected pPs, pSp, pSs, and pPp phases. The seismograms have been laterally shifted to correct for the incident angle. The direct P phase would arrive at time zero but has been muted out.

View larger version (68K): [in this window] [in a new window]   Figure 4. Gaussian beam migration of synthetic receiver functions. (A) Gaussian beam (GB) migration of the surface-reflected pPp phase on the Z component. (B) GB migration of the ps-direct P-to-S scattered phase on the X component. (C) This shows the GB migration of surface reflected pPs phase on the X component. Note the better depth resolution compared with the migration of the ps phase. (D) Product of the ps and pPs GB migrations.

View larger version (99K): [in this window] [in a new window]   Figure 5. Synthetic seismic data convolved with an observed seismic pulse from the 1993 Cascadia experiment. In these plots, the synthetic data, including the direct wave, are convolved with an observed vertical component trace from the 1993 Cascadia data set. (A) The X component record section is shown convolved with the observed trace. (B) This shows the Z component record section convolved with the observed trace. (C) This shows the filtered autocorrelation of the convolved X component. (D) This shows the filtered autocorrelation of the Z component.

View larger version (49K): [in this window] [in a new window]   Figure 6. Gaussian beam migrations of the Z component and X component filtered autocorrelations. (A) Gaussian beam migration of the Z component autocorrelation for the pPp phase. The result is lower frequency than the equivalent receiver function migration, but the primary parts of the structure can be seen. (B) Gaussian beam migration of the X component of the autocorrelation for the pPs phase.