Attenuation-compensated reverse time migration of GPR data constrained by resistivity

Abstract

The high-frequency electromagnetic waves of ground-penetrating radar (GPR) attenuate severely when propagated in an underground attenuating medium owing to the influence of resistivity, which remarkably decreases the resolution of reverse time migration (RTM). As an effective high-resolution imaging method, attenuation-compensated RTM (ACRTM) can effectively compensate for the energy loss caused by the attenuation related to media absorption under the influence of resistivity. Therefore, constructing an accurate resistivity-media model to compensate for the attenuation of electromagnetic wave energy is crucial for realizing the ACRTM imaging of GPR data. This study proposes a resistivity-constrained ACRTM imaging method for the imaging of GPR data by adding high-density resistivity detection along the GPR survey line and combining it with its resistivity inversion profile. The proposed method uses the inversion result of apparent resistivity data as the GPR RTM-resistivity model for imposing resistivity constraints. Moreover, the hybrid method involving image minimum entropy and RTM is used to estimate the medium velocity at the diffraction position, and combined with the distribution characteristics of the reflection in the GPR profile, a highly accurate velocity model is built to improve the imaging resolution of the ACRTM. The accuracy and effectiveness of the proposed method are verified using the ACRTM test of the GPR simulated data of a typical attenuating media model. On this basis, the GPR and apparent resistivity data were observed on a field survey line, and use the GPR resistivity-constrained ACRTM method to image the observed data. A comparison of the proposed method with the conventional ACRTM method shows that the proposed method has better imaging depth, stronger energy, and higher resolution, and the obtained results are more conducive for subsequent data analysis and interpretation.