浅部频率域电磁勘探方法综述  

Frequency-domain electromagnetic methods for exploration of the shallow subsurface:A review

作　　者：汤井田[1,2] 任政勇[1,2] 周聪[1,2] 张林成[1,2] 原源[1,2] 肖晓[1,2] 

机构地区：[1]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,长沙410083 [2]中南大学地球科学与信息物理学院,长沙410083

出　　处：《地球物理学报》2015年第8期2681-2705,共25页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41104071;41574120;41174105);国家高技术研究发展计划(863)项目(2014AA06A602);国家重点基础研究发展规划(青年973)项目(2015CB060201)资助

摘　　要：适用于近地表(2000m以内)勘探的频率域电磁法主要有音频大地电磁法(audio-frequency magnetotellurics,AMT),无线电大地电磁法(radio-magnetotellurics,RMT),可控源音频大地电磁法(controlled source audiofrequency magnetotellurics,CSAMT),广域电磁法(Wide Field Electromagnetic Method,WFEM).本文拟从最新的数据采集技术、数据处理技术、正反演算法、实例等四个方面,论述适用于浅部勘探的AMT,RMT,CSAMT和WFEM方法的国内外最新进展,总结目前AMT,RMT,CSAMT和WFEM方法遇到的困难,对潜在的发展方向提出建议.综述表明:(1)张量测量、多站阵列、多站叠加可提高AMT、RMT和CSAMT数据的质量.利用近区数据WFEM法可获得良好的效果.国产与国外仪器在质量方面的差距正在逐步缩小.(2)数学形态滤波技术、Hilbert-Huang变换等可有效分离出有用的数据,局部畸变仍然是亟待解决的难题,需要更为深入的研究.(3)矢量有限元与非结构网格的出现大幅度提高了有限元处理复杂电磁问题模拟的精度与应用范围,成为目前电磁正演的首选工具.完全非线性反演算法仍然局限于1D、2D问题,共轭梯度法和高斯牛顿算法等为解决3D问题的发展趋势.地质约束的引入和多数据联合反演可以减小反演的非唯一性.各向异性的反演为目前反演研究的热点之一.(4)野外数据解释的正确性严重依赖于对地下结构先期的维性判别,在2D特性不明显、3D特性明显时,需要采用3D进行反演解释.Four electromagnetic（EM）methods are widely used in exploration of the shallow subsurface（above depth 2000meters）,which are the audio-frequency magnetotellurics（AMT）,radio-magnetotellurics（RMT）,controlled source audio-frequency magnetotellurics（CSAMT）and the wide-field electromagnetic methods（WFEM）.The purpose of this review is to present the advances of these technologies from five aspects,i.e.data collection,data processing algorithms,forward modeling,inversion algorithms and case studies.We also point out theircurrent difficulties and suggest the potential development trends.To address the issues above,we have made a detailed investigation to the recent literature and chosen the most significant papers published.（1）Data acquisition and instrument.Along with the growing power of EM data collection instruments,the tensor measurement has been commonly adopted.In order to obtain more reliable data,instrument array or multi-instruments have been widely used in the field.By large funds for developing instruments,the quality of domestic instruments is gradually approaching that of the foreign equipment.（2）Data processing algorithms.The time series of AMT data usually contains different types of noise,such as artificial square waves and industry noise around target zones.Therefore,the signal-to-noise ratio of AMT data is usually low.In order to obtain useful signals, we can utilize the robust digital morphological filtering technology.In transforming the time domain signal into the frequency domain,the Hilbert Huang transform is a suitable choice.Recently,the main reliable approach to estimate the tensor impedance is simultaneously using multi-channel multi-frequency data.As for the CSAMT and RMT methods,the state of art in the data acquisition is to identify near field and far field zones.A new idea is the wide-band electromagnetic acquisition technique,which presents a unified way to compute the apparent resistivity in both near field and far field zones.Compared to the AMT,RMT and CSA

关 键 词：近地表勘探 频率域电磁法 AMT RMT CSAMT WFEM 

分 类 号：P631[天文地球—地质矿产勘探]