field comparison of Fresnel zone and ray-based GPR ttenuation-difference tomography for time-lapse imaging of lectrically anomalous tracer or contaminant plumes

Ground-penetrating radar GPR attenuation-difference tomography is a useful tool for imaging the migration of electrically anomalous tracer or contaminant plumes. Attenuation-difference tomography uses the difference in the trace amplitudes of tomographic data sets collected at different times to image the distribution of bulk-conductivity changes within the medium. The most common approach for computing the tomographic sensitivities uses ray theory, which is well understood and leads to efficient computations. However, ray theory requires the assumption that waves propagate at infinite frequency, and thus sensitivities are distributed along a line between the source and receiver. The infinite-frequency assumption in ray theory leads to a significant loss of resolution both spatially and in terms of amplitude of the recovered image. We use scattering theory to approximate the sensitivity of electromagnetic EM wave amplitude to changes in bulk conductivity within the medium.