Full-wave EM modeling of geophysical instruments in tilted planar-layered, generally anisotropic and lossy media

We propose a full-wave methodology to numerically model, using plane wave expansions (PWE), electromagnetic (EM) radiation by sources in planar-layered, generally anisotropic/lossy media possessing tilted interfaces. This method finds use in modeling responses of subsurface sensors near complex geological structures (e.g., angular unconformities), which ordinarily PWE cannot model due to requiring parallel interfaces. Previously, only “brute-force” methods (e.g., Finite Difference) could full-wave model these complex structures, but they can consume high compute resources/time and fail due to low-frequency instability. Our methodology leverages Transformation Optics, mapping the original (tilted-layer) geometry to a new one containing parallel interfaces coated by doubly-anisotropic slabs (PWE-solvable). This discontinuous mapping however, which physically implies reflective coating slabs, bounds the range of tilting our method can reliably model. Within these constraints, our results show interesting symmetry and differential sensitivity behavior to tilting, suggesting the tensorial measurements´ exploitation for detecting more complex geological structures than previously practical.