An Imaging Algorithm For Gpr Data

Abstract

The finite difference time domain (FDTD) method is calculated by the explicit finite approximation scheme of Maxwell’s curl equations. Since it allows arbitrary electrical conductivity and permittivity variations within a model, the FDTD method has become one of the powerful forward modeling methods for electromagnetic (EM) phenomena. On the other hand, the reverse time migration is the imaging algorithms, which is performed by inserting the recorded data as boundary conditions at each recorder position in reverse time order. Due to the advantage of simple calculation algorithm and applicability to arbitrary model, both methods are powerful tools for GPR. In the present paper, the synthetic GPR data are calculated by using of the FDTD method with the exploding reflector method. The reverse time migration is formulated using FDTD scheme and applied to model with lossless and lossy media. In lossless media, the forward and reverse time schemes are expressed by the completely same scheme. The proposed method is successfully applied to synthetic data for two models, these are steeply dipping structure and point diffractors model. In lossy media, the forward scheme includes diffusion term, while the reverse time scheme includes divergence term. In such a case, we show the condition that the EM wave velocity is regarded as constant, then this methodology is applicable successively. We also discuss the reverse time migration for the lossy media after the amplitude recovery under the lossless media condition.