ELECTROMAGNETIC RESPONSE OF TWO-DIMENSIONAL INHOMOGENEITIES IN A DISSIPATIVE HALF-SPACE FOR TURAM INTERPRETATION *

An integral equation technique based on the integral formulation of the electric field of a harmonically excited line-source in the presence of a two-dimensional scattering in-homogeneity is outlined. In this treatment the inhomogeneity is assumed to have an arbitrary cross-sectional shape and to be located in a layered, dissipative half-space. The scattering responses in terms of the horizontal and the vertical magnetic field components observed on the ground surface are studied for a variety of geologic models involving overburden layers, vertical or inclined veins and multiple inhomogeneities. The horizontal component of the total magnetic field appears to be the most diagnostic response parameter. A thin vein shaped target with a cross sectional area of 0.05 δ₂× 0.50 δ₂ (δ₂ being the skin-depth in the lower half-space) located 0.50 δ₂ away from the line-source and under a highly conductive overburden layer (σ₁/σ₂= 300) of thickness 0.02 δ₂ is easily detected with a moderate resolution. The scattering responses are also sensitive to changes in depths of burial, inclination and conductivity contrast with the surrounding half-space of the target inhomogeneity. An interpretation scheme as well as a number of characteristic detectability parameters are developed for the conventional Turam method used in mineral exploration.