Utilizing diffractions in wavefront tomography

Wavefront tomography is known to be an efficient and stable approach for velocity inversion, which does not require accurate starting models and does not interact directly with the prestack data. Instead, the original data is transformed to physically meaningful wavefront attribute fields. These can be automatically estimated using local coherence analysis by means of the commonreflection-surface (CRS) stack, which has been shown to be a powerful tool for data analysis and enhancement. In addition, the zero-offset wavefront attributes acquired during the CRS stack can be used for sophisticated subsequent processes such as wavefield characterization and separation. Whereas in previous works, wavefront tomography has been applied mainly to reflection data, resulting in smooth velocity models suitable for migration of targets with moderately complex overburden, this work has the emphasis on utilizing the diffracted contributions in the data for velocity inversion. By means of simple synthetic examples we demonstrate the potential of diffractions for velocity inversion. On industrial field data we suggest a joint inversion based on reflected and diffracted contributions of the measured wavefield, which confirms the general finding that diffraction-based wavefront tomography can help to increase the resolution of the velocity models. Concluding this work, we compare the quality of a reverse-time migrated result using the estimated velocity model with the result based on the inversion of reflections, which reveals an improved imaging potential for a complex salt geometry