地电阻率法中勘探深度和探测范围的理论讨论和计算

本文对地电阻率法中两个常用的基本概念——勘探深度和探测范围进行了理论探讨和计算,分析了电法勘探中关于这两个概念的若干问题和不足。为了适应地电阻率法比较台址条件和研究其探测能力的需要,在分析这些问题的基础上,运用层状介质视电阻率的理论公式提出了勘探深度的新定义。用统一的标准给出了若干不同电性结构、不同装置下的勘探深度的定量结果,并具体讨论了探测范围上、下界面理论位置与介质表层及深部电性变化量大小、装置极距、仪器精度等参数之间的关系。指出在均匀介质、四极对称装置下,利用精度为1级的仪器探测下界面的最大深度可达极距AB的1.5倍左右的新结论,以及给出了加大探测范围的理论途径。最后本文还讨论了两个概念的差异和联系以及在一般非均匀介质条件下求得勘探深度的原则方法。

THEORETICAL DISCUSSION AND CALCULATION ABOUT DETECTI-VE DEPTH AND DETECTIVE RANGE IN EARTH RESISTIVITY METHOD

Two fundamental concepts-detective depth and detective range mostly used in apparent resistivity method have been studied theoretically.Some problems including deficiencits about these two concepts in electrical pro-specting have been discussed in this pager.In order to compare the under-ground condition of stations and study detective capability of stations,a sort of new definition of detective depth has been proposed,based on the theoritical formula of apparent resistivity in layered-medium.The detective depths in different structures and arrangements of current electr-ods have been quantitatively calculated under a unified standard.Besides,the relations between the theoritical positions of upper and lower in-terface of detective range in media and the parameters such as the mag-nitude of variation of resistivity in the top-Layer or deep-Layer,the distance of current electrods and the precision of instruments bave been discussed.The calculation indicates that the maximun detective depth of the lower interface in media can be about 1.5 times as much as the dis-tance between electrods AB in homogeneous media,using Symmetrical-Four-Pole-arrangement and instruments whose precision is 1.0.The approach of increasing detective range have been suggested theoretically.This paper also discusses the difference and the relation between these two concepts as well the method of calulating detective depth in inhomo-geneous media in principle.