Very low frequency magnetotelluric and dipoledipole responses of threedimensional thinlayer resistivity structure modeled using finite elements
Abstract
An algorithm to simulate the very low frequency magnetotelluric and dipoledipole responses of threedimensional thinlayer inhomogeneity has been developed from an existing finite element program used to simulate resistivity/IP signatures of 2D earth sections. The 3D body is confined to and extends uniformly across a thin layer overlain by air and underlain by infinite resistivity. Electric fields are obtained through differentiation of piecewise parabolas fit to nodal voltages while magnetic fields arise from integration of the freespace Green's tensor over secondary current perturbations throughout the thin layer. Dipoledipole apparent resistivities arise through application to nodal voltages of the logarithmic geometric factors appropriate to continuously grounded line sources of current. Checks on accuracy of the simulation utilize analytic solutions, 2D AC planewave results using finite elements, and a surface integral equations technique.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 September 1985
 Bibcode:
 1985STIN...8620693W
 Keywords:

 Dipole Moments;
 Electrical Resistivity;
 Finite Element Method;
 Magnetic Anomalies;
 Magnetic Surveys;
 Very Low Frequencies;
 Algorithms;
 Computerized Simulation;
 Current Density;
 Plane Waves;
 Electronics and Electrical Engineering