Migrating Steep-Obliquity Interfaces in GPR Images Based on a Crossed Differential Operator

Abstract

Subsurface mapping can be implemented by the migration imaging of ground penetrating radar (GPR) data. Finite difference (FD)-based migration can effectively achieve fast imaging in media with lateral heterogeneity. However, this migration inherently suffers from insufficient accuracy in determining the true morphology of any steep-obliquity interface. In this letter, we propose a new algorithm based on crossed differential operator (CDO) and reverse-time migration (RTM) strategy to refocus the reflections back into its precise location. By employing the implicit Crank–Nicolson scheme without any operator approximations, wave field can be extrapolated nearly along the characteristic directions of wave propagation based on the nonapproximate equations. We determined the potential of the algorithm using synthetic and field data. For synthetic data, we consider a multigeometry scenario, including different angle interfaces, different-sized spheres, and lateral heterogeneity. In particular, we focus on extrapolation accuracy, amplitude–frequency focusing ability, entropy analysis, and imaging errors. In the field data test, we found that the finer morphology of the steeper-obliquity interfaces can be determined, the interpretability and amount of discernible details can also be improved. This improvement makes CDO-based migration a very promising tool for the finer imaging of shallow subsurface.