The three dimensional 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 to validate both algorithms. Unlike HSBA, SAMM is not a perturbative algorithm and does not require small dielectric or volumetric perturbations of the half-space geometry. In general, SAMM is a faster method and for inverse problems, key scattering features can often be determined with low-order modes, sacrificing precise field details in favor of computational speed. By contrast, the HSBA method allows scatterers to be continuously distributed, and one can ""reuse"" HSBA results once the time-consuming problem-specific Green's function is calculated for the underlying geometry, needing only a fast matrix multiplication for the particular scatterer(s).


Poster presented at the 2007 Thrust R1B Effective Forward Models Conference


Semi-Analytic Mode Matching (SAMM), borehole

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Algorithms, Three-dimensional imaging




Bernard M. Gordon Center for Subsurface Sensing and Imaging Systems (Gordon-CenSSIS)

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Bernard M. Gordon Center for Subsurface Sensing and Imaging Systems (Gordon-CenSSIS)

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