摘要
本文讨论了时间域电磁法(TEM)中电偶源发射时垂直磁场及其导数的一维正演计算问题.对利用余弦变换从频率域的正演结果转换到时间域的过程中存在的实、虚部的选取,磁场和磁场导数的精度问题进行了较详细的研究.指出用Hz(ω)的虚部导出的Hz(t)精度较高,而ε(t)的结果无论是采用Hz(ω)的实、虚部都不太理想。还提出了在晚期用Hz(t)数值差分的方法也能获得较好的(dH(t)/(dt))结果。文中对ε(t)的早、晚期视电阻率定义和Hz(t)的全区定义进行了比较。指出Hz(t)的全区定义视电阻率同时具有ε(t)早、晚期定义视电阻率的有效特征,曲线形态简单,易于解释。然而,ε(t)的全区定义可能在很多情况下出现“无意义”的现象,曲线形态复杂,不宜采用。最后,作者建议把野外测得的感应电动势ε(t)数值转换为磁场Hz(t),并求出其全区定义视电阻率,与ε(t)的结果同时用于解释.并用实例说明从ε(t)到Hz(t)的转换是可行的,也是非常有效的.
It is proved that the transient electromagnetic (TEM)metbod in which measurements are made alter primary field has been cut off is superior and is used increasingly for mineral and petroleum explorations. In this paper, we present a modified Cosine Transform Method to transform the direct problem of EM sounding to TEM sounding, and prove that whole-domain apparent resistivity for vertical magnetic field Hz(t) is much more effective than other type of the apparent resistivities used in TEM. And a method to transform EMF data in loop measurement to Hz(t) data is recommended.
出处
《物探化探计算技术》
CAS
CSCD
1993年第2期108-116,共9页
Computing Techniques For Geophysical and Geochemical Exploration
