  This paper deals with the solution of Maxwell's equations to model the
electromagnetic fields in the case of a layered earth. The integrals involved
in the solution are approximated by means of a novel approach based on the
splitting of the reflection term. The inverse problem, consisting in the
computation of the unknown underground conductivity distribution from a set of
modeled magnetic field components, is also considered. Two optimization
algorithms are applied, based on line- and global-search methods, and a new
minimization approach is presented. Several EM surveys from the ground surface
are simulated, considering the horizontal coplanar (HCP) and perpendicular
(PRP) magnetic dipolar configurations. The numerical experiments, carried out
for the study of river-levees integrity, allowed to estimate the errors
associated to these kind of investigations, and confirm the reliability of the
technique.
