CSAMT法三维分辨能力及其物理机制

The study on the resolution and physical mechanism of CSAMT exploration for 3D model

随着CSAMT法探测应用需求的日益增多,其分辨能力及其物理机制的研究成为人们不得不面对的问题.在CSAMT勘探中,几何效应、电流效应和感应效应是引起电磁场变化的三种物理机制,本文详细介绍了与地下电性结构密切相关的电流效应和感应效应.首先,利用CSAMT法对100 m×100 m×100 m的异常体进行了探测,研究表明存在两个畸变区域.利用电流效应对存在的两个畸变区域进行了解释,进一步研究表明当收发距为10 km时电流效应占据主要地位,感应效应位居次要地位,当收发距增大时电流效应比重下降,感应效应比重增大.选取坐标原点位于电偶极子中心,x方向为电偶极矩方向,z轴垂直向下,随后,研究了CSAMT法对异常体沿x、y及z方向长度变化时的探测灵敏度,研究表明CSAMT法对异常体沿x方向的变化最为灵敏、y方向变化次之、z方向最为迟钝,最后对以上现象给出了解析.

With the increasing applications of CSAMT exploration, it is becoming to be very important to solve the problems of the resolution and physical mechanism of CSAMT exploration. In CSAMT exploration, there are three physical mechanisms to produce the electromagnetic field changes in amplitude and phase, which are geometric effect, the galvanic effect and induced effect. This paper describes the galvanic effect and induced effects, which are closely linked to CSAMT exploration. It shows that the resolution of CSAMT is very good for single anomalous body of 100 m× 100 m×100 m, but there are two distortion zones. In this paper, we use the galvanic effect to explain the reasons for the two distortion zones. The studies show that in this simulation, the current produced by the galvanic effect ismore donimant than the current produced by the induced effect. We also studied the resolution sensitivity of CSAMT for x, y and z directions of an anomaly body. The study shows that CSAMT is most sensitive to resolve the changes in x-direction, less sensitive in y direction followed, and the least in z direction. We also explained the reasons of this phenomenon.