Theory and application of Gaussian beam depth migration

The Gaussian beam is high-frequency approximate solution that wave equation centralized around the ray, which closely combines wave equation with the ray theory to get raypath through kinematical ray tracing and to get high-frequency energy near central ray through dynamic ray tracing. The individual Gaussian beam is used to carry out the wavefield propagation and it retains the kinematical characteristics, while it keeps the dynamic features of wavefield at the same time. Gaussian beam depth migration (GBM), propagating each ray by a Gaussian beam form and summing the contributions from all the individual beams to produce the wavefield, is an accurate, flexible and efficient migration method, with the ability to image steeply dipping reflectors and anisotropic medium, and also, to extract Angle Domain Common Imaging Gathers (ADCIGs) directly through wavefield direction vector by computing traveltime gradient which is restricted in the effective region of a Gaussian beam. In this paper, the basic principle and strategy of GBM are introduced; the technology to yield ADCIGs by Gaussian beam migration is also shown. Numerical tests on synthetic data and real data sets demonstrate the Gaussian beam migration method is effective.