矩形框瞬变电磁法一维正演研究

The Study on 1D Forward Algorithm of Rectangular Loop TEM

为研究一维情况下以矩形框、圆形框作为发射源的瞬变电磁响应之间的差异,首先利用电磁学中的互易定理将矩形框发射源的瞬变电磁响应转化为一系列圆形框发射源瞬变电磁响应的积分形式,进而推导出矩形框发射源的瞬变电磁法一维正演表达式。然后以推导的正演算法为基础,编写出正演程序,计算出二层、三层地电模型的瞬变电磁响应曲线,并对比分析了理论情况下的矩形、圆形线框作为发射源的响应曲线。结果显示:在较小时刻两者差异较小,在较大时刻两者差异较大,矩形框的感应电动势直接代入传统的瞬变电磁反演程序计算时电阻率可能存在误差。

In order to study the differences of transient electromagnetic response between rectangular transmitting loop and circular transmitting loop,In this paper,the formula of the TEM Response of rectangular transmitting loop by using the reciprocity theorem and the response expression of circular transmitting loop is deduced.On the basis of the forward algorithms,the forward modeling method is introduced in this paper.In addition,many other 1Dforward model have been done,such as the two layers of D,G electric model,three layers of Q,A,H,K electric model.And the response curve of rectangular transmitting loop is also presented.By numerical calculation,the TEM response of rectangular and circular transmitting loop is compared.The results were that the difference of these induced emfs was relatively less at relatively smaller time and induced emfs was relatively larger at relatively larger time,and the direct use of induced emfs of rectangular loop for inversion and calculation directly may cause errors.