关于层状介质视电阻率响应系数的研究

THE STUDY ON THE RESPONSE COEFFICIENTS IN THE APPARENT RESISTIVITY IN HORIZONTAL LAYERED MEDIUM

摘要:

本文从水平层状介质的电法理论出发,定义了电性层的响应系数S_i,并指出:S_i代表各层电阻率的变化对△ρs/ρs贡献的"权",同时还给出了二层、三层和深埋电极时Si的计算公式和部分计算结果,着重讨论了电性结构对表层响应系数S1和底层响应系数S_n的影响。最后以此理论讨论了九个地电台站的具体情况。
根据理论和实际资料的分析,得出以下几点结论:
1)从电性上,台址最佳观测条件是:表层响应系数S₁=0;底层响应系数S_n=1。
2)台址的表层电阻率ρ₁高一些,底层电阻率ρ₃低一点,比较接近最佳观测条件。但各层电阻率之间的搭配关系需有一定范围,过高或过低的值都会偏离最佳观测条件。
3)仅仅以电性剖面类型区分台址电性条件的优劣是不完善的,最好通过具体计算S₁来评判。

Abstract:

In this paper,the response coefficient Si of geoelectrical leyers is defined on the basis of the theory of the resistivity method in horizontal layered-medium.It is pointed out that the Si represents weight of contribution to Δρs/ρs by variations of the resistivity of the layers.Then the expressions of Si about two-layer,three-layer and the case of the deep buried electrode are brought out and some of numerical results and also obtained.Especially we have a discussion about the influence of the geo-electrical structure on the overlayer response coefficient Si and the deep-layer response coefficient Sn.Finally,by means of this theory on Si the practical cases about nine stations are discussed.
In accordance with this theory and practical data we can gain the conclusions as follows.
1) As for electrical property,the best-observing conditions for resistivity method stations are
overlayer response coefficient S₁=0
deep-layer response coefficient S_n=1
2) The best observing condition for the station site chosen is that the overlayer resistivity may be greater and the deep layer,S smaller.The relation of the resistivities of the layers needs an opposite range of its value.When the value is too large or too small,a deviation from the best-observing conditions takes place.
3) It is not enough for a station to be selected only by the kinds of geoelectrical profiles.To determine a station site,Si is always needed calculating with carefulness.