张继锋^1,,
刘寄仁²,
冯兵^1,,,
董岩¹,
郑一安¹
1. 长安大学地质工程与测绘学院, 西安 710054
2. 中南大学地球科学与信息物理学院, 长沙 410083

基金项目: 国家重点研发计划项目(2017YFC0602200)之课题"航空地球物理综合处理解释方法研究及软件开发"(2017YFC0602202)，国家自然科学基金(41830101)和四川省峨眉至汉源高速公路工程科研项目(LH-HT-45)联合资助


详细信息

作者简介: 张继锋, 1978年生, 副教授, 主要从事电磁法理论及正反演研究.E-mail: zjf0201@126.com

通讯作者: 冯兵, 1962年生, 副教授, 主要从事电磁勘探理论及应用研究.E-mail: fb8005@126.com

中图分类号: P631

收稿日期:2020-04-03
修回日期:2020-10-08
上线日期:2021-04-10

Three-dimensional response of the 3D grounded multiple-source airborne EM system in the frequency domain

ZHANG JiFeng^1,,
LIU JiRen²,
FENG Bing^1,,,
DONG Yan¹,
ZHENG YiAn¹
1. School of Geology Engineering and Geomatics, Chang'an University, Xi'an 710054, China
2. School of Geosciences and Info-Physics of Central South University, Changsha 410083, China


More Information

Corresponding author: FENG Bing,E-mail:fb8005@126.com

MSC: P631

--> Received Date: 03 April 2020
Revised Date: 08 October 2020
Available Online: 10 April 2021


摘要
摘要:地空电磁法已经成为深部资源勘探的重要地球物理方法，但对频率域地空系统的三维多源电磁响应特征研究较少.本文设计了多种激励源组合方式，采用非结构化有限元数值模拟方法，对三维地电模型的空中垂直磁场的响应特征进行了研究.首先推导了基于电场的双旋度公式及其变分形式，加入罚项以减少伪解的影响.接着把有限元稀疏矩阵方程转换为频率的函数，采用Krylov子空间投影方法，通过模型降阶算法降低稀疏矩阵的阶数，实现多频点的快速计算.建立了三维低阻体模型、高阻体模型以及两个相邻低阻体模型，分别采用单源、双源、三源和四源激励模式，从垂直磁场的总场、二次场响应和全域视电阻率等方面进行分析比较.结果表明：多源地空电磁法不仅可以增加总场的强度，而且可以改变异常体的二次电磁响应分布规律.各电偶源延长线呈正三角形分布的三源和矩形分布的四源激励模式在增强信号强度以及削弱异常体的边界效应方面具有一定的优势，是一种优化的多源激励方式.
关键词: 地面电性源/
地空电磁系统/
多源/
电磁响应/
数值模拟

Abstract:The ground-airborne frequency domain electromagnetic method has become an important geophysical method for deep resource exploration. However, there are few studies on 3D multiple-source electromagnetic response characteristics of the grounded-airborne system in the frequency domain. In this work, we design a variety of excitation source combinations and analyze vertical magnetic field response characteristics of the 3D geoelectric model by using an unstructured finite element numerical simulation method. First, a double curl formula based on the electric field and its variational form are derived, and a penalty term is added to reduce the influence of the false solution. Then the finite element sparse matrix equation is converted into a function of frequency. By using a Krylov subspace projection method and reducing the order of the sparse matrix through model reduction algorithm, we realize fast computation for multiple frequencies. Through three established 3D models, one is low-resistance, the other is high-resistance and the last is an adjacent low-resistance body, with different (single, double, triple and four) source excitation, we compare the responses of the total and secondary field of the vertical magnetic field and the full-time apparent resistivity. The results show that the multiple-source ground-airborne electromagnetic method can not only increase the intensity of the total field, but also change the distribution pattern of the secondary electromagnetic response of the anomaly body. The triangular-distributed three-source and the rectangular-distributed four-source excitation modes along the extended line of the electric dipole source has certain advantage in terms of enhancing signal strength and weakening the boundary effect of abnormal objects, which is an optimized multiple-source excitation manner in practical application.
Key words:Ground electrical-source/
Ground-airborne electromagnetic system/
Multiple-source excitation/
Electromagnetic response/
Numerical simulation



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