均匀半空间CSAMT折线形线源的场源数值模拟  

Numerical simulation of the field source for the CSAMT folded line source in a homogeneous half-space

作　　者：段跃权 刘云[1] 王紫郡 李雨珊 DUAN Yue-Quan;LIU Yun;WANG Zi-Jun;LI Yu-Shan(School of Earth Sciences,Yunnan University,Kunming650500,China)

机构地区：[1]云南大学地球科学学院,云南昆明650500

出　　处：《物探与化探》2024年第1期151-161,共11页Geophysical and Geochemical Exploration

基　　金：云南大学第十四届研究生科研创新项目(KC-22221593)。

摘　　要：可控源音频大地电磁法(CSAMT)在野外进行测量时,通常认为发射线源是简化为长度极小的电偶极子源,但是在野外实测中,CSAMT发射线源都是折线形布设。本文在前人研究成果的基础上,根据电磁场的线性叠加原理推导出折线形电流线源激发的电磁场数值计算方法,通过对不同的折线形线源模型进行计算,分析均匀半空间情况下折线形线源对视电阻率、阻抗相位曲线的影响。模型计算表明折线形线源对视电阻率、阻抗相位曲线的近区和过渡区有较大影响,远区则不受影响;近区和过渡区受到的影响主要是由各个折线段的方位角引起,折线段方位角越大,对测点的视电阻率和阻抗相位的影响越大。当折线段方位角很小时,可以将其忽略并近似为直线源进行处理,这样既可以充分考虑发射源的形态又可以提高工作效率。为后续CSAMT数据处理的近场校正以及CSAMT数值模拟提供了理论支持。For field surveys using the controlled source audio magnetotelluric(CSAMT)method,it is generally believed that the CSAMT line source is a simplified electric dipole source with a minimal length.However,CSAMT line sources are all arranged in a fol-ded line pattern in field surveys.Based on the previous research results,this study derived the numerical calculation method for the e-lectromagnetic field excited by the folded line source according to the linear superposition principle of electromagnetic fields.Through the calculation of different folded line source models,this study analyzed the influences of the folded line source on the apparent resis-tivity and impedance phase curves in the homogeneous half-space.Model calculations demonstrate that the folded line source signifi-cantly influenced the near and transition zones of the apparent resistivity and impedance phase curves but had no influence on their far zones.The influences on the near and transition zones were primarily caused by the azimuths of folded line segments,and higher azi-muths were associated with more significant influences on the apparent resistivity and impedance phase of survey points.In the case of very low azimuth angles,the folded line source can be approximated as a straight line source for processing,improving the work effi-ciency while fully considering the morphology of the emission source.This study provides theoretical support for the near-field correc-tion of subsequent CSAMT data processing and the CSAMT numerical simulation.

关 键 词：CSAMT 非直线型接地电缆源 均匀半空间 折线形线源 线性叠加 

分 类 号：P319.3[天文地球—固体地球物理学]