基于有限体积的半航空瞬变电磁任意各向异性三维正演及响应规律分析  

Three-dimensional forward modeling and response analysis of semi-airborne transient electromagnetic with arbitrary anisotropy based on finite volume method

作　　者：姜晓腾 孙怀凤[1,3,4] 刘东 柳尚斌 王震[1,3,5] 周小生 杨静 JIAGN XiaoTeng;SUN HuaiFeng;LIU Dong;LIU ShangBin;WANG Zhen;ZHOU XiaoSheng;Yang Jing(Geotechnical and Structural Engineering Research Center,Shandong University,Jinan 250061,China;Guangxi Communications Investment Group Co.,Ltd.,Nanning 530022,China;Laboratory of Earth Electromagnetic Exploration,Shandong University,Jinan 250061,China;Advanced Exploration and Transparent City Innovation Centre,Shandong Research Institute of Industrial Technology,Jinan 250061,China;Beijing Research Institute of Shandong University,Beijing 100086,China)

机构地区：[1]山东大学岩土与结构工程研究中心,济南250061 [2]广西交通投资集团有限公司,南宁530022 [3]山东大学地球电磁探测研究所,济南250061 [4]山东省工业技术研究院先进勘探与透明城市协同创新中心,济南250061 [5]山东大学北京研究院,北京100086

出　　处：《地球物理学进展》2024年第5期2046-2058,共13页Progress in Geophysics

基　　金：国家重点研发计划(2022YFC3005601);广西重点研发计划(桂科AB22080010)联合资助。

摘　　要：半航空瞬变电磁地面发射、空中接收的特点,不仅能获得信噪比高的数据,而且具有极高的作业效率.然而,目前的半航空瞬变电磁研究大多针对三维各向同性介质,各向异性研究较少,对存在明显电各向异性区域的数据按照各向同性模型解释会严重偏离真实情况.开发考虑各向异性的三维正演算法,对电各向异性区域数据的正确解释具有重要意义.本文从双旋度电场方程出发,基于有限体积法以及后退欧拉法完成对空间和时间的离散,通过对主轴各向异性电导率张量做欧拉旋转得到任意各向异性电导率张量,实现半航空瞬变电磁任意各向异性三维正演算法.首先通过对一维各向异性层状模型计算,验证了本算法的正确性;其次对主轴各向异性模型进行模拟并分析了主轴各向异性对衰减电压的影响;之后,模拟计算了任意各向异性模型,并分析各向异性倾角和走向角对响应的影响;最后检验本算法对复杂地质模型模拟情况.实验结果证明了本算法可以用于半航空瞬变电磁三维任意各向异性正演,模拟结果精度较高.Most research on transient electromagnetic phenomena in the field of airborne electromagnetics focuses on three-dimensional isotropic media,with limited studies on anisotropy.Interpreting data from regions with significant electrical anisotropy using isotropic models can lead to significant deviations from reality.To analyze the impact and extent of electrical anisotropy on transient electromagnetic signals from long conductive sources,this study employs a finite volume-based three-dimensional forward modeling algorithm for arbitrary anisotropic media.By solving the discretized full tensor conductivity time-domain electromagnetic field equations,a methodology is developed.First,based on Maxwell,s equations,and employing the background and anomaly separation theory,the computational domain is divided into a homogeneous half-space and an anomalous body.The electromagnetic response of the homogeneous half-space serves as the background field,while the electromagnetic response of the anomalous body forms the anomaly field.The curl equation of the electric field anomaly is further curled to obtain the curl equation for the secondary electric field.Integrating the curl equation for the secondary electric field within a control volume yields an integral equation.Applying Gauss,s theorem converts the volume integral equation into a surface integral equation,which is then discretized for independent computation on the surface.Employing backward Euler algorithm in the time domain leads to the final discrete equation.To enhance accuracy and efficiency of time-domain electromagnetic field solution,the algorithm combines time segmentation with direct equation solving.The algorithm,s validity is verified through one-dimensional anisotropic layered model calculations.Subsequently,the impact of principal axis anisotropy on attenuation voltage is simulated and analyzed.Arbitrary anisotropic models are then simulated and the effects of anisotropic dip and azimuth angles on the response are investigated.Finally,the algorithm,s simu

关 键 词：半航空瞬变电磁 有限体积 各向异性 三维正演 

分 类 号：P631[天文地球—地质矿产勘探]