覆盖层影响下圆锥型瞬变电磁Occam约束反演  

Conical source transient electromagnetic response characteristics with overburden based on Occam constrained inversion

作　　者：李哲 杨海燕[2] 岳建华[2] 刘志新[2] 姜志海[2] 苏本玉[2] 张华 汪凌 杨夫杰 LI Zhe;YANG Haiyan;YUE Jianhua;LIU Zhixin;JIANG Zhihai;SU Benyu;ZHANG Hua;WANG Ling;YANG Fujie(School of Geophysics and Measurement and Control Technology,East China University of Technology,Nanchang 330013,China;School of Resources and Geosciences,China University of Mining and Technology,Xuzhou 221116,China)

机构地区：[1]东华理工大学地球物理与测控技术学院,江西南昌330013 [2]中国矿业大学资源与地球科学学院,江苏徐州221116

出　　处：《煤田地质与勘探》2022年第6期175-183,共9页Coal Geology & Exploration

基　　金：国家自然科学基金项目(41974086,41974128);东华理工大学研究生创新基金项目(YC2020-S484)。

摘　　要：在地表浅层瞬变电磁勘探中,覆盖层是影响瞬变电磁探测效果的重要因素之一。为了进一步验证覆盖层影响下圆锥型场源装置的探测效果,在瞬变电磁全区视电阻率理论基础上,引入地层信息约束的Occam反演方法,研究了覆盖层不同参数影响下下伏地层的电磁响应特征。研究结果表明:目标层电磁响应强度与覆盖层和目标层电阻率比值有关;当覆盖层电阻率逐渐增大时,目标层反演电阻率与实际电阻率拟合度呈现先提升后降低的趋势,临界点出现在覆盖层与下伏高阻层电阻率相等时;当覆盖层厚度增大时,下伏地层的电磁响应相应减弱,异常区电磁响应峰值出现时间提前,反演后电阻率峰值深度加深。通过加入地层信息约束,下伏地层电阻率与实际电阻率拟合度及层界面分辨率均得到有效提升。研究成果为圆锥型场源野外数据处理与解释提供理论参考。The overburden thickness and conductivity can affect transient electromagnetic response in shallow subsur-face investigation.In order to further verify the overburden detection effect with a conical source device,combining all-time apparent resistivity conversion of transient electromagnetic field,the electromagnetic response characteristics of the underlying strata influenced by the overburden was studied by introducing an Occam inversion with stratum information constraints.The results indicate that electromagnetic response intensity of the target layer is related to the resistivity ra-tio of the overburden to the target layer.With the overburden resistivity gradually increasing,the resistivity fitting de-gree between inversed data and real value increases and then decreases.The critical point appears at the moment of the overburden resistivity equaling to the underlying high-resistivity layer.The electromagnetic response of the underlying stratum attenuates with the overburden thickness increases,which leads to the abnormal peak of the electromagnetic re-sponse coming earlier,and the inversed resistivity peak depth increasing.Besides,by using constrained stratigraphic in-version,the inversion fitting degree and the layer interface resolution can be improved.The research can provide a theor-etical reference to the design of measurement parameters and data processing and interpretation.

关 键 词：瞬变电磁法 圆锥型场源 覆盖层 全区视电阻率 模型约束 OCCAM反演 

分 类 号：P631[天文地球—地质矿产勘探]