Experimental time-domain controlled source electromagnetic induction for highly conductive targets detection and discrimination

Experimental Time-domain Controlled Source Electromagnetic Induction for Highly Conductive Targets Detection and Discrimination. (May 2007) Alfonso Benavides Iglesias, B.S; M.A.S., Universidad Central de Venezuela Chair of Advisory Committee: Dr. Mark E. Everett The response of geological materials at the scale of meters and the response of buried targets of different shapes and sizes using controlled-source electromagnetic induction (CSEM) is investigated. This dissertation focuses on three topics; i) fractal properties on electric conductivity data from near-surface geology and processing techniques for enhancing man-made target responses, ii) non-linear inversion of spatiotemporal data using continuation method, and iii) classification of CSEM transient and spatiotemporal data. In the first topic, apparent conductivity profiles and maps were studied to determine self-affine properties of the geological noise and the effects of man-made conductive metal targets. 2-D Fourier transform and omnidirectional variograms showed that variations in apparent conductivity exhibit self-affinity, corresponding to fractional Brownian motion. Self-affinity no longer holds when targets are buried in the near-surface, making feasible the use of spectral methods to determine their presence. The difference between the geology and target responses can be exploited using wavelet decomposition. A series of experiments showed that wavelet filtering is able to separate target responses from the geological background. In the second topic, a continuation-based inversion method approach is adopted, based on path-tracking in model space, to solve the non-linear least squares problem for unexploded ordnance (UXO) data. The model corresponds to a stretchedexponential decay of eddy currents induced in a magnetic spheroid. The fast inversion