Admittance inversion of crosshole radar data

In this paper, a new inversion approach has been proposed using the ratio of two mutually orthogonal components of recorded electric and magnetic fields: apparent admittance. This study aims at the development of a full waveform inversion algorithm in two-dimension (2D) without the precise knowledge of source functions and without any compensations of 3D nature of radar wave propagation. To alleviate local minima problems, we developed a data weighting method based on the data misfits. The developed inversion approach was firstly demonstrated through inverting 2D FDTD simulation data of crosshole radar survey with false source signatures. Further demonstrated was that the numerical data simulated in the 3D space could be inverted by the proposed 2D algorithm with the 2D FDTD forward modeling. All numerical experiments showed that the material property distribution with remarkably high accuracy can be calculated in spite of the lack of the accurate source information and no compensations of the characteristics of radar wave propagation in 3D space.