Lossy Half-Space Born Approximation Modeling of Electromagnetic Wave Source and Scattering in Soil by Cross Well Radar

Sensing of dense non-aqueous phase liquids (DNAPLs) in soils with cross-well radar (CWR) is a challenging geophysical problem that can have significant benefits in geo-environmental applications. Method development and implementation involve forward modeling of electromagnetic source (antenna) and wave propagation in soils, subsurface sensing and reconstruction of the contrasting DNAPL volume. In particular, modeling the antenna behavior in soil is critical because the soil background greatly affects its radiation characteristics. An analytical model is implemented in the frequency domain in terms of the dyadic Green's function solution to describe the physical nature of an ideal dipole source in infinite soil medium half-space. This Green's function model is then incorporated into a first order Born Approximation to linearize the inverse scattering problem. EM wave propagation behavior is studied over a wide frequency band and various soil moisture contents. The forward modeling simulation is compared with experimental data collected using subsurface cross-well radar using broadband antennas. Soil parameter calibration is performed based on this forward model to approximate the most likely soil property in laboratory environment. The calibrated soil parameters are then applied in simulation to compare with fields generated by monopole antennas in the laboratory.