电导率连续变化的瞬变电磁2.5维正演

I present a method for calculating transient electromagnetic response caused by a central loop source over a 2-D structure, in which the electric property parameter is continuously within each block. The governing Maxwell equations are firstly transformed into the Laplace and along-strike spatial Fourier domains. Two coupled linear-differential equations result whose dependent variables are the along-strike components of the electric and magnetic fields. The Galerkin method is used to derive the finite-element equations. The main difference between my forward method and those previous works is the definition of conductivity parameter. During the work, I describe the variety of conductivity parameter in each element not constant but linear. In addition, the total electromagnetic field is separated into a background and a secondary field to avoid a soured singularity: the background field is solved using analytical method and only the secondary field cause by anomalous bodies is computed numerically. Finally, the TEM 2.5-D responses over several typical geoelectric models are presented.