关键词: 瞬变电磁场, 时域有限差分, 扩散, 滞后

Abstract: In this paper we analyze the transient responses directly in frequency-domain using time-domain difference (FDTD). Since two-dimensional structure is convenient to be shown by figures, we use line source 2D geo-electrical models. By computing “smoke ring” diffusion in the earth and vertical electromotive force on the earth about uniform two-layer and uniform two-layer with a conductor indicates that transient fields have delay phenomenon. It means that once an anomalous body causes transient responses, this response might delay a long time. In engineering explorations, we have used later time delay to prospecting sallower bodies, such as abandoned coal miners located at 20m～150m depth range and have had good results. The numerical resolutions of this study support the previous practices theoretically.

Key words: Transient electromagnetic field, Time-domain finite difference, Diffusion, Delay