Wave-equation migration techniques offer an attractive alternative to widespread Kirchhoff methods for 3-D prestack depth migration, with modern powerful computing resources. Several authors have recently illustrated these techniques' potential for handling multi-pathing problems and complex velocity media Biondi (1997); Mosher et al. (1997); Vaillant et al. (2000). This study focuses on the particular case of the common-azimuth migration (CAM) method and discusses the accuracy of its approximations.
Common-azimuth migration is a 3-D prestack depth migration
technique based on the wave equation Biondi and Palacharla (1996). It exploits the
intrinsic narrow-azimuth nature of marine data to reduce its
dimensionality. Migration is performed iteratively through
common-azimuth downward-continuation of the wavefield. This
common-azimuth downward-
continuation operator is derived from the
stationary-phase approximation of the full 3-D
prestack downward
continuation operator. Thus, the CAM approach manages to cut the
computational cost of 3-D imaging significantly enough to compete with
Kirchhoff methods.
Even though CAM is designed for 3-D migration in complex media, we used here only synthetic data and 1-D velocity models. Our purpose was to identify better its behavior on simple examples. In this paper, we first discuss wave propagation in constant gradient velocity media and then analyze migration results of synthetic data.