Three-Dimensional Reverse Time Migration of Ground-Penetrating Radar Signals

Three-dimensional (3D) ground-penetrating radar (GPR) systems and 3D seismic imaging techniques have been developing fast and evolving rapidly in the last decade. Ray-based migration methods have been successfully applied to processing 3D GPR signals based on the similarity between electromagnetic and seismic waves. However, reverse time migration (RTM) of 3D GPR signals has not been well studied in the past. In this paper, we present a 3D RTM based on Maxwell’s equations for 3D GPR surveys. Migration recovers the true subsurface structure from a distorted and unfocused time profile and suppresses common electromagnetic clutter and noise. RTM based on Maxwell’s equations can consider conductivity directly and compensate for the attenuation within a high-conductivity zone. Compared with 2D RTM, 3D RTM back-propagates both in-line and cross-line signals simultaneously and can include complex 3D permittivity and conductivity models. We have integrated a parallel finite-difference time-domain (FDTD) algorithm based on a hybrid MPI and OpenMP scheme to reduce the computational cost of 3D problems. The 3D RTM experiments on an anomaly of “EM” shape and a realistic sand dune model demonstrate the effective recovery of 3D subsurface structures.