瞬变电磁法对低阻薄层的分辨能力研究  

STUDY ON TEM′S RESOLUTION CAPABILITY FOR THE THIN LAYER OF LOW RESISTIVITY

作　　者：王战军[1] 朱自强[1] 李建慧[1] 鲁光银[1] 赵云威[1] 彭凌星[1] 

机构地区：[1]中南大学地球科学与信息物理学院,湖南长沙410083

出　　处：《物探化探计算技术》2012年第6期646-651,619-620,共6页Computing Techniques For Geophysical and Geochemical Exploration

基　　金：国家自然科学基金项目资助(41174061);湖南省自然科学基金项目资助(11JJ3042)

摘　　要：从垂直磁偶极源激发的频率域电场出发,采用回线源瞬变电磁法一维正演方法,分别计算了低阻薄层随埋深厚度比和电阻率差异比变化时的感应电动势。依据电磁法探测的体积效应,对传统二分法进行了改进并定义了全区视电阻率的计算方法,并在此基础上分别绘制了低阻薄层埋深厚度比为1∶1.2、1∶1.5、1∶2及1∶4,电阻率差异比为1∶5、1∶10及1∶20的视电阻率曲线。通过对比不同地电模型视电阻率曲线的特征,指出了不同电阻率差异比时,瞬变电磁法对低阻薄层的分辨极限,归纳了瞬变电磁法对低阻薄层的识别及分辨能力,这对于研究地下水平层状介质的垂直电性变化具有重要意义。Starting from frequency-domain electric field excited by vertical magnetic dipole,we derived one-dimensional forward method of Loop source,and calculated induced electromotive force on the thin layer of low resistivity while the ratio of depth and thickness and difference in the resistivity changes.In accordance with volume effect of electromagnetic method,we improved traditional dichotomy and proposed the method of calculating the whole stage apparent resistibity.And then on this basis we draw the curves of apparent resistivity when the ratio of depth and thickness is 1∶1.2,1∶1.5,1∶2,1∶4 and the ratio of resistivity is 1∶5,1∶10,1∶20 respectively.By comparing the characteristics of all kinds of apparent resistivity curve for different geoelectric models,we pointed out the resolution limit of TEM for low-resistivity thin layer of specific kinds and summarized the capacity of TEM for identifying and distinguishing low-resistivity thin layer,which is important to study the response of horizontal layered medium.

关 键 词：瞬变电磁法 低阻薄层 改进二分法 全期视电阻率 分辨能力 

分 类 号：P631.325[天文地球—地质矿产勘探]