| The frequency domain electromagnetic response of a thin vertical tabular plate in a conductive two-layer earth can be obtained by solving the electric field integral equation using the method of point collocation with global test functions. When it is assumed that the components of the scatter current perpendicular to the plate edges vanish at the plate edges, and when test functions are chosen which satisfy this condition, EM responses can usually be obtained for plates ranging from the resistive to the inductive limits. For highly resistive host media, numerical failure occurs when the plate conductivity is high enough that magnetic effects predominate. The solution is valid over a sufficiently wide range of parameters as to permit the computation of horizontal loop (Slingram) profiles over a plate in a layered earth. Suites of horizontal loop Argand diagrams are presented which illustrate the peak (in-phase and quadrature) anomaly values for a plate imbedded in a conductive earth. The suites show anomaly enhancement and phase rotation due to the conductive host and can be used to obtain, from field surveys, estimates of conductor depth and conductivity-thickness which are independent of the prospecting frequency. |
