Explicit prestack depth migration in laterally varying VTI media

Abstract

We present an efficient and stable method for wave equation prestack depth migration (PSDM) in laterally varying VTI media. The method accurately handles large lateral variations in the Thomsen anisotropy parameters, ? and ?, as well as vertical velocity. It performs wavefield extrapolation using a constrained explicit operator that we originally proposed and successfully applied for isotropic wave equation PSDM. The constrained operator has a reduced number of independent coefficients, leading to improved migration efficiency whilst retaining accuracy. The optimization process for the operator design ensures that we can quickly design a large number of well-behaved operators for different combinations of velocity and anisotropy parameters. Model and field data examples show that the migration method proposed is able to produce well focused and correctly positioned images in areas of complex geology.