频散介质中的瞬变电磁响应特征和反演特性分析  

Transient electromagnetic responses and inversion characteristics in dispersion medium

作　　者：智庆全 武军杰[1,2,3] 王兴春 杨毅[1,2,3] 张杰 邓晓红[1,2,3] ZHI Qingquan;WU Junjie;WANG Xingchun;YANG Yi;ZHANG Jie;DENG Xiaohong(Institute of Geophysical and Geochemical Exploration,Langfang 065000,China;Laboratory of Geophysical EM Probing Technologies,MNR,Langfang 065000,China;State Research Center of Modern Geological Exploration Engineering Technology,Langfang 065000,China;College of Geological Engineering and Geomatics,Chang’an University,Xi’an 710054,China)

机构地区：[1]中国地质科学院地球物理地球化学勘查研究所,廊坊065000 [2]自然资源部地球物理电磁法探测技术重点实验室,廊坊065000 [3]国家现代地质勘查工程技术研究中心,廊坊065000 [4]长安大学地质工程与测绘学院,西安710054

出　　处：《物探化探计算技术》2022年第2期251-260,共10页Computing Techniques For Geophysical and Geochemical Exploration

基　　金：国家重点研发计划重点专项(2018YFC0603803);中央级公益性科研院所基本科研业务专项(AS2020J01,AS2019P01,AS2020Y01)。

摘　　要：真实大地固有频散特性,较强的频散效应叠加到瞬变电磁响应之中,会给传统的数据处理手段带来困难。目前考虑频散效应的瞬变电磁数据多参数联合反演解释方法,具有显著的多解性和初始模型依赖。为分析这种现象产生的原因,并探究可能的解决途径,这里首先引入Cole-Cole模型,结合数字滤波方法实现了频散介质中瞬变电磁响应的正演,通过与前人结果对比验证了正演方法的有效性。以典型的电模型为基础,分析了频散介质中瞬变电磁响应规律、单调性和灵敏度特征。采用多参数联合反演中常用的目标函数,分析了反演目标函数的形态、极值点、平滑度等特性,探讨了适合频散介质中瞬变电磁响应的反演策略。研究表明,频散介质中的瞬变电磁响应特征具有明显的非单调性,频率相关系数和时间常数的灵敏度特性较差,反演目标函数具有大量的局部极小和尖锐的全局极小,全局优化算法是较适合此反演问题的寻优策略,但仍需引入目标函数改造或参数约束等手段以改善反演过程的收敛性。Due to the inherent dispersion properties of the earth,a strong dispersion effect superimposed on transient electromagnetic responses will bring difficulties to traditional data processing.At present,the multi-parameter joint inversion interpretation method of transient electromagnetic data considering the dispersion effect has significant multi-solution and initial model dependence.In order to analyze the causes of this phenomenon and explore possible solutions,we realized the forward modeling of transient electromagnetic response in the dispersion medium by introducing the Cole-Cole model and digital filtering method.The effectiveness of the forward modeling method was proved by comparing it with previous results.Based on a typical geoelectrical model,the characteristics,monotonicity,and sensitivity of transient electromagnetic responses in dispersion medium were analyzed.Using the common objective function in multi-parameter joint inversion,the characteristics of the inversion objective function,such as morphology,extreme point,and smoothness,were analyzed,and then the inversion strategy suitable for transient electromagnetic response in dispersion medium was discussed.Results show that the transient electromagnetic response characteristics in the dispersion medium are non-monotonic,the sensitivity characteristics of frequency dependence and time constant are poor.The inversion objective function has a large number of local minima and a sharp global minima,and the global optimization algorithm is possibly a better optimization strategy for the inversion problem.However,modification of objective function or parameter constraint method should be introduced to improve the convergence of the inversion process.

关 键 词：瞬变电磁法 频散效应 数值模拟 反演 

分 类 号：P631.2[天文地球—地质矿产勘探]