Full-waveform Modeling and Joint Inversion of Electromagnetic Induction and Ground Penetrating Radar Data

Existing ground penetrating radar (GPR) and electromagnetic induction (EMI) sensors present some limitations related to their calibration procedure and the strong simplifying assumptions in modeling the antenna-subsurface system. We present a new EMI model in which a zero-offset, off-ground loop antenna is efficiently modeled using frequency-dependent, complex linear transfer functions. The air-subsurface is described by a Green’s function for wave propagation in three-dimensional multilayered media. We validated our model in laboratory conditions by performing measurements at different heights above a copper sheet as a perfect electrical conductor. Then joint inversion of full-waveform mono-static GPR and EMI data was carried out for the particular case of a one-layered medium. Analysis of the objective functions demonstrated the benefit of combining the two sources of information. Yet, due to the variations of the GPR and EMI model sensitivities with respect to the properties of the medium, the formulation of an optimal objective function is not straightforward.