A new method of array processing, called Interferographic transient electromagnetics (ITEM), of semi-airborne multi-source, multi-receiver TEM data is introduced using beamforming techniques to synthetically form impulsive distributions of TEM fields that partially unmix diffusive EM field structure and improve resolution of subsurface geoelectric structure. ITEM differs from applications of the wave propagation synthetic aperture concept to diffusive EM geophysics. The synthetic aperture concept is incomplete, achieving no vertical compaction, for TEM beamforming. ITEM achieves full beamforming by using both spatial and temporal sets of subsurface electric field distributions to form a two-dimensional (2D) digital filter. Significant impulsive EM field compaction in both horizontal and vertical dimensions results. ITEM is described for a 2D geometry with a semi-airborne survey design. ITEM processing is applied to a reference model set of electric field distributions as well as both reference model and acquired magnetic field profiles. The resulting filtered distributions are quickly translated into a subsurface resistivity image using a simple image formation process. An example for a synthetic geoelectric structure is provided that demonstrates ITEM processing and subsurface imaging.

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