Target-oriented wavefield tomography using demigrated Born data

tomographic inversion results

We have performed wavefield tomography using the new data set modeled from the selected target image as discussed in the previous section. We minimize the combined objective function $J$ (equation 11) using a nonlinear conjugate-gradient solver. Figure 7(a) shows the inverted velocity model after $6$ nonlinear iterations and Figure 7(b) shows the true velocity model. The nonlinear inversion has successfully recovered the two anomalies below the salt. The migrated image and gathers using the inverted velocity model and the original data set are shown in Figure 8 (compare it with the results obtained using the starting velocity model shown in Figure 2). The SODCIGs obtained using the inverted velocity model (Figure 8) are more focused at the zero subsurface offset and the horizontal reflector is flatter compared to those obtained using the starting velocity model (Figure 2). For comparison, Figure 10 shows the migration results obtained using the true velocity model.

bwi-sigsb2c-vmod-invt-target,bwi-sigsb2c-vmod-target
Figure 7. (a) The inverted velocity model and (b) the true velocity model. [CR]

bwi-sigsb2c-imag-invt-target
Figure 8. The migrated target image and gathers using the inverted velocity model (Figure 7(a)) and the original data. View descriptions are the same as in Figure 2. [CR]

bwi-sigsb2c-bimg-target
Figure 9. The migrated target image and gathers using the starting velocity model and the original data. View descriptions are the same as in Figure 2. [CR]

bwi-sigsb2c-imag-target
Figure 10. The migrated target image and gathers using the true velocity model and the original data. View descriptions are the same as in Figure 2. [CR]

Target-oriented wavefield tomography using demigrated Born data