Angle-Domain Differential Reflection Traveltime Tomography

Abstract

Seismic reflection tomography based on prestack depth migration has been widely used for seismic imaging in the presence of complex geology. However, it still has some well-known and unfavorable features, such as slow convergence and requirements of many rounds of migration and residual moveout picking. To avoid the dependence on the unknown true depths of the reflection interfaces and to mitigate the ill-condition of the inverse problem, we propose a differential reflection tomography approach based on the angle-domain common-image gathers. The objective of our method is to iteratively update the velocity model so that the depth deviations between pairs of adjacent incident angles are minimized. Eigenvalue analysis of the tomographic matrices indicates that the conditioning is improved by our double-difference measurement instead of the commonly used float-datum criterion. Aiming at a stable and efficient velocity update, we introduce a structure-oriented model regularization and multi-level grid refinement in each round of residual moveout picking. Synthetic and field data examples show that the proposed approach can successfully retrieve the velocity structures for seismic imaging using fewer rounds of prestack depth migration and residual moveout picking.