CSRMT正交水平发射源电磁场分布规律研究
Distribution patterns of the electromagnetic fields of orthogonal horizontal magnetic dipoles as sources in CSRMT
陈兴朋 1王亮 1龙霞 1席振铢 2亓庆新 1薛军平 1戴云峰 3胡子君4
作者信息
- 1. 湖南五维地质科技有限公司,湖南 长沙 410205
- 2. 中南大学 地球科学与信息物理学院,湖南长沙 410083
- 3. 南京水利科学研究院 水文水资源与水利工程科学国家重点实验室,江苏 南京 210029
- 4. 湖南女子学院 信息科学与工程学院,湖南 长沙 410004
- 折叠
摘要
可控源射频大地电磁法(controlled source radio-magnetotellurics,CSRMT)测量通常使用发送频率 1～1 000 kHz的人工场源,正交水平电偶源和正交水平磁偶源是人工源电磁法众多发射源中实现张量电阻率测量的优质场源.为此,本文基于水平电偶极子源和水平磁偶极子源电磁场解析公式,计算了均匀半空间模型正交水平电偶极子源和正交水平磁偶极子源的电磁场.结果表明,发射频率大于 100 kHz时,应考虑位移电流;而张量视电阻率和阻抗相位在远区可以忽略位移电流的影响;固定模型电阻率、改变收发距时,模型计算表明高频电磁场远区测量范围更大;固定收发距、改变模型电阻率时,模型计算表明电磁场远区范围受电阻率影响较大,高阻模型需要更高的频率才会出现远区观测条件.磁偶源相较于电偶源,在张量视电阻率和相位上与实际值的偏差更小,更适于地质分析.
Abstract
Controlled source radio-magnetotellurics(CSRMT)measurements typically use artificial field sources transmitting at fre-quencies ranging from 1 to 1 000 kHz.Among the many transmitting sources of the artificial source electromagnetic method,the orthog-onal horizontal electric dipole source and the orthogonal horizontal magnetic dipole source are preferred field sources for tensor resistivity measurements.Hence,using the analytical formulas for electromagnetic fields based on the horizontal electric dipole source and the horizontal magnetic dipole source,this study calculated the electromagnetic fields based on the orthogonal horizontal electric dipole source and the orthogonal horizontal magnetic dipole source in the homogeneous half-space model.The results show that:(1)The dis-placement current needs to be considered at transmitting frequencies above 100 kHz;(2)The effects of displacement current on the tensor apparent resistivity and the impedance phase can be ignored in the far zone;(3)With a constant model resistivity and varying distances between transmitter and receiver,model calculations indicate a larger measurement range in the far zone of the high-frequency electromagnetic field;(4)With a constant distance between transmitter and receiver and varying model resistivities,model calculations suggest that the far-zone range of the electromagnetic field is significantly influenced by resistivity,and that the high-resistivity model requires higher frequencies for achieving far-zone observation conditions.Compared with the electric dipole source,the magnetic dipole source exhibits smaller deviations on the tensor apparent resistivity and impedance phase with the actual value,which is more suitable for geological analysis.
关键词
可控源射频大地电磁法/正交水平电偶源/正交水平磁偶源/位移电流/阻抗Key words
controlled source radio-magnetotellurics(CSRMT)/orthogonal horizontal electric dipole source/orthogonal horizontal magnetic dipole source/displacement current/impedance引用本文复制引用
基金项目
国家重点研发计划(2022YFC2903404)
国家重点研发计划(2022YFC2900002)
出版年
2024
国家科技期刊平台
NSTL
万方数据