Improved resistivity imaging of targets with sharp boundaries using an iterative disconnect procedure

The smoothness constraint inversion is not appropriate for imaging sharp targets such as archaeological structures. Alternative approaches requires either a priori information about the subsurface (e.g., disconnect inversion) or requires two or more geophysical datasets to be collected at the same site (e.g., joint inversion). Here we propose a 3-D inversion strategy that does not require a priori information and is theoretically more appropriate for imaging targets with sharp resistivity contrasts. Our approach combines an initial smoothness constraint inversion that is used only at the first iteration to recover a resistivity model that is fairly consistent with the measured data, from which an initial target location is estimated using an edge detector method and from which a disconnect in the inversion is identified. This disconnect defining the target outline is then progressively improved following each iteration of the inverse procedure. We applied our approach on 3-D synthetic studies that include a single cavity, and widely-and closely-spaced cavity models. In addition, we tested our approach on a challenging synthetic field model scenario that simulates archaeological field sites in Egypt. Synthetic studies demonstrate the effectiveness of our approach in recovering both resistivity and geometry of buried targets over the smoothness constraint inversion approach.