FREQUENCY-WAVE-NUMBER MODELING AND MIGRATION OF 2D GPR DATA IN MODERATELY HETEROGENEOUS DISPERSIVE MEDIAL

An algorithm for modelling and migrating ground penetrating radar (GPR ) data in moderately heterogeneous dispersive media is presented. The method is based on wavefield extrapolation in the frequency-wavenumber (f-k) domain, from the solution of the 2D Maxwell's equations. The wa vefield is extrapolated by a phase-shift technique using a constant re lative permittivity It and a quality factor e. It is then modified by a correction term to handle the lateral K and Q variations. The spatia l distribution of the K and Q-factor values, representing the given mo del parameters, is introduced into the algorithm by a regular grid par ametrization. The radar wave dispersion and attenuation, induced by re laxation processes, are taken into account by a linear frequency-depen dent Q model, and expressed by a complex wavenumber in the propagation equation. A synthetic case and a field data set illustrate the potent ial of the method for frequencies of 300, 500 and 900 MHz. In the firs t case, a typical civil engineering problem is considered. The frequen cy dependence of the wave velocity and attenuation is well illustrated . The synthetic data are afterwards migrated using the initial model p arameters. The results show the importance of using spatially varying model parameters in the migration processes. The second case concerns an application of the method to a real data set. In order to adjust th e model parameters, a forward modelling sequence is performed until th e best match between the measured and the synthetic data is achieved. A depth migration is then applied to the data, and the result is compa red with the initial model parameters. In conclusion, we assess the co ntributions of the method to industrial applications, by discussing th e performance of the algorithm compared with its limitations.