中文摘要：

定源回线装置的瞬变电磁法因其发射磁矩强,勘查深度大主要用于详查阶段来确定目标地质体的中心、埋深、边界以及倾角等几何参数.定源回线装置条件下一般测量三个分量的瞬变响应数据,而目前流行的解释方法仅为一维反演和视电阻率成像,并且大多只利用单个分量,还未充分利用三分量瞬变响应的有用信息.目前还缺少实用快速的实现三维三分量反演的有效方法.为充分利用实测三分量瞬变响应数据,并且获得更加可靠的目标地质体的信息,本文提出了基于等效电流环的三分量纯异常三维反演方法.理论表明受激发的导电体产生的涡旋电流早期分布在边缘或表面,之后向中心位置移动.即涡旋电流可以用不同时刻的等效电流环来等效,早期的电流环反映异常体的边界,而晚期的电流环主要反映异常体的中心.因此通过反演不同时刻等效电流环的几何参数,可以获得目标地质体的几何形态.本文给出了自由空间电流环产生的三个分量磁场的表达式,并利用计算得到的三分量磁场值同时拟合由实测数据提取的纯异常三分量数据,最终获得不同时刻的等效电流环的参数.理论模型和实测数据反演结果表明,等效电流环反演结果能够较好确定导电体的中心位置、半径、埋深、倾向、倾角等几何参数.本文提出的基于等效电流环的解释方法同时利用三个分量数据,计算快速、可靠、使反演结果更加合理,为定源回线装置瞬变电磁法提供了一种有效的解释方法.

英文摘要：

Fixed loop transient electromagnetic method（TEM）is used in the detailed investigation to detect the center,depth,boundary,dip and other geometry parameters of the geologic target,due to its large transmit magnetic moment and great detection depth.Generally,TEM response is observed with three components in fixed loop configuration.However most of the interpretation methods are only1 Dinversion or apparent resistivity imaging with only using one component response,and the three component response has not been used effectively.The fast and effective methods to realize 3D inversion with three component response are lacking.To use the three component response effectively and to obtain more reliable information of geological target the 3D inversion method with three component pure anomaly response based on the equivalent filament theory is introduced in this paper.The theory show that the eddy only distributes in the edge or surface of conductive body excited by primary field at early time,and then move to the center because of the interaction effect of current filaments.In other words,the vortex current can be equivalent as filaments at different times.The filament of early time reflects the edge of abnormal body,and the filament of late time reflects the center.Consequently,the geometric morphology of geological target can be obtained through the inversion of different time filaments.This paper gives the expressions of the three component of the magnetic field produced by current filament in free space,and the method how to get the filament parameters by using the computational data to fit pure anomaly data extract from field data.Model and field inversion results show that the equivalent filament can provide the center,radius,depth,dip direction and angle reliably.The method of 3Dinversion method based on the equivalent filament theory with three component response introduced in this paper is quick,reliable and it can make the inversion result more reasonable.