next up previous print clean
Next: Conclusions Up: Diffraction-focusing WEMVA example Previous: Imaging of GPR data

Discussion

Diffracted events contain useful velocity information that is overlooked by conventional MVA methods, which use flatness of common image gathers as the only criterion for the accuracy of migration velocity. In this section, I demonstrate that accurate interval-velocity updates can be estimated by inverting the results of a residual-focusing analysis of migrated diffracted events. To convert residual-focusing measurements into interval-velocity updates, I employ the WEMVA methodology (wemva) which is ideally suited for this task because it is capable of inverting image perturbations directly, without requiring an estimate of the reflector geometry. In contrast, ray-based MVA methods require the reflector geometry to be provided by interpreting the migrated image. However, since the interpretation of partially-focused diffracted events is an extremely difficult task, ray-based methods are never employed for diffraction-focusing velocity analysis.

The seismic-data example demonstrates how the WEMVA method can exploit the velocity information contained in the event generated by a rugose salt-sediment interface. This kind of events is present in many salt-related data sets, and the ability of using the diffracted energy to further constrain the velocity model might significantly improve the final imaging results.

The GPR-data example demonstrates the significant potential of the WEMVA method for improving the imaging of GPR data. I demonstrate that the interval-velocity model obtained by extracting velocity information from the diffracted events improves the reflector continuity in the migrated image and facilitates geological interpretation of the images. Since a large number of GPR data sets are limited to zero-offset data, the possibility of using diffractions to define the lateral variations in interval velocity can substantially widen the range of applications of GPR methods.


next up previous print clean
Next: Conclusions Up: Diffraction-focusing WEMVA example Previous: Imaging of GPR data
Stanford Exploration Project
11/4/2004