磁性层状介质的CSAMT电场分量响应特征

在传统的勘探电磁学理论中,往往把岩层磁导率近似看成空气中的磁导率,从而得到简化后的电磁场响应式,主要用于指导非磁性介质情况下的电磁探测.本文开展了磁性介质的电磁响应理论、数值模拟和特征分析等研究,以便实现对磁性矿体的电磁精细探测.首先推导出磁性层情况下的电磁响应表达式;然后,计算了几种典型磁性介质地质断面的响应曲线,并对其响应特征进行了分析;研究结果表明:当磁性层位于地表时,当表层相对磁导率μr1.2,磁性层对电磁测深曲线具体明显的影响;当岩层为中间层时,只要μr1.2,对H型、A型曲线中段会有影响.对H型曲线,主要表现在使极小值处的曲线抬高、变宽,以致使曲线形态发生变化;当磁性层处于最后一层时,不论岩层的磁导率是多少,对各类二、三层曲线来讲,不会影响曲线的形态,只是使渐近线前第一个极值点的位置右移,极值点至渐近线之间的线段变得较为陡峭.

Response of CSAMT electromagnetic component in the magnetized layered earth

In the traditional exploration electromagnetic theory, the rock permeability is usually regard as the air permeability approximately. As a result, the electromagnetic field response can be derived simply. However, study on electromagnetic response considering rock permeability is required for fine electromagnetic detection of magnetic ore bodies. In this paper, electromagnetic field response expressions of the magnetic layered earth is deduced at first, then the response curves of several kinds of typical magnetic medium geological sections are calculated. The research results show that electromagnetic sounding curves are heavily affected by the rock permeability layer when the earth is covered by a magnetic layer with rock permeability μ_r>1.2. While as H-type and A-type curves are heavily affected by rock permeability (μ_r>1.2) for the middle layer. On the other hand, when the magnetic layer is buried as the basement, electromagnetic sounding curves are slightly affected by the rock permeability layer.