Semi-Analytic Mode Matching (SAMM) algorithm for efficient computation of nearfield scattering in lossy ground from borehole sources

The 3D semi-analytic mode matching (SAMM) algorithm is used to determine nearfield scattering from underground targets in lossy soil, where the source is a dipole placed within a borehole in the ground. Scattering is described by moderately low-order superpositions of spherical modes placed at multiple user- specified coordinate scattering centers (CSCs); the mode coefficients are found numerically by least-squares fitting all boundary conditions at discrete points along the relevant interfaces while at the same time obeying radiation conditions. SAMM results are compared with a completely different method: the Half-Space Born Approximation (HSBA). Good agreement between methods serves as algorithm validation.