Electromagnetic Subsurface Imaging. A Case for an Adaptive Born Approximation

The process of interpretation of electromagnetic data has many facets of which fast approximate interpretation techniques is an intriguing one. A new variant of the Born approximation – the Adaptive Born approximation – is presented and exemplified through 1D and 2D imaging techniques for transient electromagnetic data. The Adaptive Born approximation is generally applicable in approximate inversion schemes for inductive electromagnetic data as a one-pass imaging algorithm. Though it is as simple to use as the ordinary Born approximation, it offers a more accurate inverse mapping.In the first part of this paper an attempt will be made to give an overview of fundamental concepts in electromagnetic subsurface imaging relevant for approximate inverse mappings and to outline major trends in present day modeling and inversion of electromagnetic data. This is of course an impossible task – certainly for this author – and much important work will not be mentioned in the limited space of the following. My apologies to the people who are not mentioned and whose research is not given credit here though it should have been. Naturally, my choice of references reflects the schools and circles I have been subjected to, but I hope that the list of references to developments in electromagnetic methods will point to papers of importance and thereby to other references for the interested reader.