Magnetotelluric Profiling of Vertical Conductors

Abstract

The presence of lateral contrasts of electrical conductivity modifies the original pattern of electromagnetic fields radiated from remote sources. A magnetic transverse plane wave field, interacting with a vertical conductive and outcropping dike placed between two quarter-spaces of unequal electrical conductivities, creates an anomalous vertical component of the magnetic field. This anomalous field has been analysed by computation, and drafting of master curves. Two case histories are presented to illustrate the application and the effectiveness of the solution. It is concluded that: (i) the response is higher for intermediate values of the conducting body induction number; (ii) the curves can be used for the interpretation of magnetotelluric, AFMAG, and VLF exploration data; (iii) it is necessary to develop solutions taking into account the vertical as well as the lateral variation of conductivity.