关于可控源音频大地电磁法探测深度的探讨

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钟幼生, 韩自强, 罗姣, 冯兵. 关于可控源音频大地电磁法探测深度的探讨[J]. 物探与化探, 2015,39(4): 768-774.
ZHONG You-Sheng, HAN Zi-Qiang, LUO Jiao, FENG Bing. A tentative discussion on the detecting depth of controlled source audio magneto telluric method[J]. Geophysical and Geochemical Exploration, 2015,39(4): 768-774. 复制到剪切板

Doi:10.11720/wtyht.2015.4.18
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关于可控源音频大地电磁法探测深度的探讨

钟幼生¹, 韩自强^2,³, 罗姣³, 冯兵³

1. 青海省第一地质矿产勘查院,青海西宁 810600

2. 招商局重庆交通科研设计院有限公司,重庆 400067

3. 长安大学地质工程与测绘学院,陕西西安 710054

作者简介: 钟幼生(1963-),男,青海西宁人,主要从事金属矿产勘查的应用研究工作。

收稿日期: 2015-02-11

基金: 国土资源部深部探测项目(SinoProbe-03-03); 国家自然科学基金面上项目(41174108)

摘要

分析了水平电偶极子源均匀半空间电磁场表达式特征,进而推广到双极源电磁场。基于双极源一维模拟结果,研究了可控源音频大地电磁法探测深度与频率、电距、收发距、覆盖层电阻率的关系。结果表明:在保证一定信噪比的前提下,决定可控源音频大地电磁法最大探测深度的是收发距和电阻率综合作用下进入过渡区及近区场时对应的频率,并不是简单的频率越小,探测深度越大。进入近区场,可控源音频大地电磁法不再具有测深能力。最后统计得到电磁场由远区进入过渡区时的 |kr|值约为4 .789,由过渡区进入近区时的 |kr|值约为0.106,进而得到卡尼亚视电阻率的最大探测深度约为0.3倍的收发距,全区视电阻率的最大探测深度为3.7倍的收发距。在某多金属矿上的勘探实例印证了上述认识。

关键词: CSAMT; 趋肤深度; 探测深度; 收发距; 全区视电阻率

中图分类号:P631 文献标志码:A 文章编号:1000-8918(2015)04-0768-07

A tentative discussion on the detecting depth of controlled source audio magneto telluric method

ZHONG You-Sheng¹, HAN Zi-Qiang^2,³, LUO Jiao³, FENG Bing³

1. First Geology and Mineral Exploration Institute of Qinghai Province, Xining 810600, China

2. China Merchants Chongqing Communications Technology Research & Design Institute Co., Ltd., Chongqing 400067, China;

3. School of Geological Engineering and Geomatics, Chang'an University, Xi'an 710054, China

Abstract

In this paper, the authors analyzed the characteristics of the horizontal electric dipole source electromagnetic expression of homogeneous half space, and then extended this expression to the bipolar source electromagnetic field. The relationships between CSAMT detecting depth and frequency, electric dipole moment, transceiver distance and the resistivity of the coating layer were studied based on bipole 1D simulation. The results show that, under the premise of guaranteed noise ratio, the factors that decide the maximum detecting depth of CSAMT method are corresponding frequencies when the detection enters the near region and transitional zone under the integrated action of transceiver distance and resistivity of the coating layer. The argument "the smaller the frequency, the larger the detecting depth' does not always hold water. When the detection enters the near region, the CSAMT method no longer has the detection capability. Statistics show that, when the electromagnetic field enters the transitional zone from the distant zone, the | kr| value is about 4.789; when the electromagnetic field enters the near zone from the transitional zone, the | kr| value is about 0.106. Then conclusions are drawn that the maximum detection depth of Cagniard apparent resistivity is about 0.3 times the transmitter receiver distance, and the maximum detection depth of full wave apparent resistivity is about 3.7 times the transmitter receiver distance. A case study has proved the above understanding.

Keyword: CSAMT; skin depth; detecting depth; transceiver distance; full wave apparent resistivity

Show Figures

可控源音频大地电磁法(CSAMT)是在音频大地电磁法(AMT)的基础上发展起来的一种人工源频率域测深方法。20世纪70年代初, 加拿大多伦多大学的D. W. Strangway 教授和他的学生M. A. Goldstein 提出沿用AMT的测量方式, 观测人工供电产生的音频电磁场, 称这种方法为CSAMT。随着计算机水平的发展, CSAMT法的2.5维和三维正演都取得了一定的研究成果 $\begin{matrix} ^{[17]} \end{matrix}$ ; 同时伴随着CSAMT法正演的发展, CSAMT法的反演研究也取得了一定的进展^{[8, 9]}。我国自20世纪80年代开展CSAMT法以来, 先后在寻找深部隐伏金属矿体、油气构造勘查、地热和水文工程等方面都取得了较好的地质效果 $\begin{matrix} ^{[1023]} \end{matrix}$ 。何继善^[24]在CSAMT法的基础上提出了广域电磁测深法, 使得CSAMT法观测范围不拘泥于波区, 扩大了测量范围; 但对于CSAMT法的探测深度, 普遍依赖于趋肤深度计算公式^[24]。陈明生提出人工源频率域电磁测深的探测深度还受收发距的影响, 不能沿用原有的趋肤深度计算公式^[25]。笔者分析了水平电偶极子源均匀半空间场电磁场表达式特征, 基于CSAMT源(双极源)一维模拟结果, 研究了CSAMT法探测深度和频率、电距、收发距、覆盖层电阻率的关系, 最后讨论了CSAMT卡尼亚视电阻率和全区视电阻率的探测深度。

1 趋肤深度

忽略位移电流, 在无磁性介质中, 趋肤深度为 δ ≈ 503 $\begin{matrix} \sqrt[]{ρ / f} \end{matrix}$ , 一般以趋肤深度作为电磁法勘探的探测深度。电磁波的趋肤深度随电阻率的增加和频率的减小而增大, 故为了寻找深部矿体和探测深部构造, 应采用较低的工作频率, 如果覆盖层的电阻率比较高, 则可利用较高的频率就可探测较深的目标体。

趋肤深度计算公式是通过平面波作为源推导得到。对于双极源场, 只有在远区才可以近似看作是平面波场, 可以用趋肤深度作为探测深度, 而在过渡区, 不能以趋肤深度作为实际勘探深度, 还应考虑收发距的影响。陈明生给出了过渡区探测深度的一般估计式:δ ≈ K $\begin{matrix} \sqrt[]{ρ / f} \end{matrix}$ , K包含了收发距的影响^[25]。

2 水平电偶极子均匀半空间E_x、H_y特征

CSAMT法发射源是双极源, 要通过对电偶极子场沿双极源的长度方向进行积分来获得双极源场^[26]。设双极源长度为L, 供电电流为I, 方向沿x轴方向, (x^*, 0, 0)为电偶极子坐标, (x, y, 0)为接收点坐标。电偶极矩为Idl的水平电偶极子在均匀半空间上的电磁场表达式为

$\begin{matrix} \begin{matrix} \bar{E_{x}} = \frac{Idl ρ_{1}}{4 π} \frac{1}{r^{3}} [3 co s^{2} φ - 2 + (1 + i k_{1} r) e^{- i k_{1} r}], (1) \\ \bar{H_{y}} = \frac{Idl}{4 π} \frac{1}{r^{2}} [(1 - 4 si n^{2} φ) I_{1} K_{1} + \\ \frac{i k_{1} r}{2} si n^{2} φ (I_{0} K_{1} - I_{1} K_{0})], (2) \\ \bar{Z_{xy}} = \bar{E_{x}} / \bar{H_{y}} 。 (3) \end{matrix} \end{matrix}$

式中:r= $\begin{matrix} \sqrt[]{x^{2} + y^{2}} \end{matrix}$ ; φ 为r和x轴方向的夹角; k₁为波数, k₁= $\begin{matrix} \sqrt[]{- iωμ / ρ_{1}} \end{matrix}$ , μ 为磁导率, ρ ₁为大地电阻率; I₀、K₀、I₁、K₁分别为零阶、一阶的第一类和第二类修正贝塞尔函数, 其宗量为ik₁r/2; $\begin{matrix} \bar{Z_{xy}} \end{matrix}$ 为阻抗。

双极源均匀半空间上的电磁场表达式为

$\begin{matrix} \begin{matrix} E_{x} = \frac{I ρ_{1}}{4 π} \int_{0}^{L} \frac{1}{r^{* 3}} [3 co s^{2} φ^{*} - 2 \\ + (1 + i k_{1} r^{*}) e^{- i k_{1} r^{*}}] d x^{*}, (4) \\ H_{y} = \frac{I}{4 π} \int_{0}^{L} \frac{1}{r^{* 2}} [(1 - 4 si n^{2} φ^{*}) I_{1}^{*} K_{1}^{*} \\ + \frac{i k_{1} r^{*}}{2} si n^{2} φ^{*} (I_{0}^{*} K_{1}^{*} - I_{1}^{*} K_{0}^{*})] d x^{*}, (5) \\ Z_{xy} = E_{x} / H_{y} 。 (6) \end{matrix} \end{matrix}$

式中:r^*= $\begin{matrix} \sqrt[]{(x - x^{*})^{2} + y^{2}} \end{matrix}$ , φ ^*为r^*和x轴方向的夹角。

首先研究水平电偶极子场的特征。在近区, 即|kr|≪1, 则式(1)和式(2)取近似得

$\begin{matrix} \begin{matrix} \bar{E_{x}} \approx \frac{Idl ρ_{1}}{2 π r^{3}} (3 co s^{2} φ - 1), \\ \bar{H_{y}} \approx \frac{Idl}{4 π r^{2}} (2 co s^{2} φ - 1), \\ \bar{Z_{xy}} \approx \bar{E_{x}} / \bar{H_{y}}, \\ ρ = \frac{(2 co s^{2} φ - 1)}{2 (3 co s^{2} φ - 1)} \bar{Z_{xy}} 。 \end{matrix} \end{matrix}$

由此可知, 在近区, $\begin{matrix} \bar{E_{x}} \end{matrix}$ 和 $\begin{matrix} \bar{H_{y}} \end{matrix}$ 都与频率没有关系, 与直流电流场相同。也就是当进入近区时, 继续降低测深频率, 则达不到测深的目的。

在远区, 即|kr|≫1, 则式(1)和式(2)取近似得

$\begin{matrix} \begin{matrix} \bar{E_{x}} \approx \frac{Idl ρ_{1}}{2 π r^{3}} (3 co s^{2} φ - 1), \\ \bar{H_{y}} \approx \frac{Idl}{4 π r^{3} k_{1}} (3 co s^{2} φ - 2), \\ \bar{Z_{xy}} \approx \bar{E_{x}} / \bar{H_{y}}, \\ ρ = \frac{1}{ωμ} | \bar{Z_{xy}} |^{2} 。 \end{matrix} \end{matrix}$

可以看出, 在远区, 即|kr|≫1, $\begin{matrix} \bar{H_{y}} \end{matrix}$ 与频率有关。因此, 改变频率可达到测深的目的。

|kr|≫1的前提是测深频率ω 无限大, 或者收发距r无限大, 或者电阻率ρ ₁无限小。根据趋肤深度的公式, 降低频率测得更深, 但当频率减小时, 也很快进入近区, 场则与频率没有关系, 达不到测深的目的, 因此降低频率测深和进入近区是一对矛盾。为了让|kr|≫1, 处于波区, 可以增大收发距来补偿频率的减小, 以达到降低频率从而提高探测深度的目的。此外, 在地层电阻率大的情况下, 进入近区较早, 在地层电阻率小的情况下, 进入近区较晚。

同样, 双极源远区和近区条件下的电磁场近似表达式, 可通过水平电偶极子源远区和近区条件下的电磁场近似表达式沿双极源长度方向进行积分来获得。前面研究了电偶极子场的特性, 而双极源场是由电偶极子场叠加而成, 因此具有与电偶极子场同样的特性。双极源依然沿用远区条件下电磁波阻抗定义的卡尼亚视电阻率, 而全区视电阻率的计算则是利用均匀半空间场表达式不断迭代计算得到^{[27, 28]}, 因此, 全区视电阻率和电磁场的性质最接近, 但其对地层电阻率特征的反映比电磁场更明显、更直观。

3 CSAMT探测深度的讨论

3.1 探测深度和电距、频率的关系

从式(4)、式(5)可以看出, 增大电流I, 只改变电磁场值, 不改变电磁场性质。双极源一维模拟采用赤道偶极装置(下同)。图1反映了视电阻率和双极源长度的关系, 无论是卡尼亚视电阻率还是全区视电阻率, 对于同一地电模型, 都不随双极源长度变化。可见, 电距只决定探测到的信号的强弱, 适当地选择电距, 保证一定信噪比即可。

图1显示, 随着频率的减小, 探测深度逐渐加大, 对1 km以下的低阻层有很好的反映。图1a中卡尼亚视电阻率曲线的尾支呈倾斜上升, 并没有反映出电阻率为100 Ω · m的基底, 这是因为随着频率降低, 已不满足远区条件, 进入了过渡区和近区, 卡尼亚视电阻率不具有测深能力。图1b显示, 在频率较高的波区, 全区视电阻率曲线形态和卡尼亚视电阻率一致, 但尾支趋近于一恒定值, 该值明显不是基底电阻率100 Ω · m, 这是因为随着频率的降低, 进入了近区场, 全区视电阻率同样不具有测深能力。

可见, 全区视电阻率勘探深度大于卡尼亚视电阻率, 能反映出过渡区的地电特征, 同样, CSAMT法在近区也不具有测深能力。因此, 就当前的可控源测深理论, 广域电磁法也只能在过渡区和远区有意义。

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	图1 视电阻率和双极源长度的关系

3.2 探测深度和收发距的关系

从式(4)、式(5)可以看出, 双极源电磁场值和收发距成反比。图2反映了视电阻率和收发距的关系。当收发距r较大时(50、100 km), 卡尼亚视电阻率对低阻层位有较好的反映; 全区视电阻率不仅对低阻层有较好的反映, 而且当 r=100 km 时, 全区视电阻率曲线的尾支趋近于基底的真实电阻率, 对基底也有很好的反映; 当收发距较小时, 全区视电阻率对5 km以下的低阻层没有反应, 这是因为当收发距较小时, 随着频率的降低, 探测深度没有到达低阻层, 便进入了近区。可见对于相同的收发距, 全区视电阻率的探测深度大于卡尼亚视电阻率的探测深度, 这是因为全区视电阻率能反映远区和过渡区的地电特征, 而卡尼亚视电阻率只能反映远区的地电特征。

在CSAMT法中, 增大收发距可以补偿频率的减小, 使场处在远区, 从而达到降低频率、提高探测深度的目的。但应注意, 随着收发距的增大, 场值会减小。因此, 实际工作中, 在保证信噪比的前提下, 要提高探测深度须增加收发距。

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	图2 视电阻率和收发距的关系

3.3 探测深度和覆盖层电阻率的关系

由趋肤深度计算公式可知, 电阻率越大, 探测深度越大。保持覆盖层、中间低阻层、基底的电阻率比率为10∶ 1∶ 10不变, 来研究双极源探测深度与覆盖层电阻率的关系。由图3可以看出, 随着覆盖层电阻率的降低, 双极源视电阻率曲线在反映出中间低阻层时的频率也在降低, 且降低的幅度在双对数坐标系里呈线性, 也即覆盖层电阻率越大, 进入近区场时的频率越高, 利用较高的频率便可达到较深的探测深度, 反之也成立。

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	图3 视电阻率和覆盖层电阻率的关系

4 视电阻率的探测深度

图4为均匀半空间电磁场的分区示意。在远区条件下的电磁场近似值和全区的电磁场是重合的, 近区条件下的电磁场近似值和全区的电磁场是重合的, 据此, 可判断均匀半空间模型进入过渡区和近区时对应的频率。电磁场处于何区, 主要取决于|kr|的大小; 令电磁场由远区进入过渡区时的|kr|为A_T, 由过渡区进入近区时的|kr|为A_N, 对应的频率分别为f_T和f_N。

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	图4 均匀半空间电磁场分区

对于不同的电阻率和收发距组合, 根据电磁场从远区进入过渡区的频率及过渡区进入近区的频率, 可得到不同组合的A_T、A_N值的分布(表1)。可以看出, 不同收发距和电阻率组合对应的A_T值和A_N值变化不大, 可以认为是近似相等的, 这也是取其平均值作为最大探测深度的依据。

表1 不同收发距和电阻率对应的A_T、A_N值

参数	$\begin{matrix} \frac{电阻率}{Ω \cdot m} \end{matrix}$	收发距/m			平均值
参数	$\begin{matrix} \frac{电阻率}{Ω \cdot m} \end{matrix}$	5 000		10 000	50 000
A_T	1	4.706	4.676	4.571	4.789
	10	4.775	4.744	4.638
	100	4.845	4.814	4.706
	1 000	4.916	4.885	4.775
	10 000	4.988	4.911	4.812
A_N	1	0.101			0.106
	10	0.102	0.101
	100	0.103	0.103	0.113
	1 000	0.105	0.104	0.114
	10 000	0.106	0.106	0.116

表1 不同收发距和电阻率对应的A_T、A_N值

经过统计得到了A_T和A_N的平均值, 于是可得到任意收发距和电阻率组合情况下电磁场进入过渡区和近区时对应的频率f_T和f_N:

f_T= $\begin{matrix} \frac{ρ A_{T}^{2}}{2 π μ_{0} r^{2}} \end{matrix}$ , f_N= $\begin{matrix} \frac{ρ A_{N}^{2}}{2 π μ_{0} r^{2}} \end{matrix}$ 。(7)

对于远区条件下定义的卡尼亚视电阻率, 在收发距和电阻率给定的情况下, 可得到进入过渡区时的频率f_T, 当频率f< f_T时, 卡尼亚视电阻率不具有探测能力。远区条件下最大探测深度可用趋肤深度δ ≈ 503 $\begin{matrix} \sqrt[]{ρ / f} \end{matrix}$ 计算, 则卡尼亚视电阻率的最大探测深度为

$\begin{matrix} D = 503 \sqrt[]{\frac{ρ}{f_{T}}} = 503 \sqrt[]{\frac{2 π μ_{0} r^{2}}{A_{T}^{2}}} \approx 0.3 r 。 \end{matrix}$

该计算结果与通常认为的CSAMT的收发距要大于0.3倍的探测深度是符合的。由于采用趋肤深度为最大可探测深度, 故实际情况远达不到0.3r的深度, 这在实际工作中要注意。CSAMT的全区视电阻率能够客观地反映出远区和过渡区的地电特征, 但不能反映近区的地电特征。若沿用同样的方法可计算出CSAMT全区视电阻率的最大探测深度为 3.7r, 当频率f< f_N时, 全区视电阻率不具有探测能力。可见, 在同样的地电条件下CSAMT全区视电阻率的最大探测深度远大于卡尼亚视电阻率的探测深度, 建议实际工作中联合应用卡尼亚视电阻率及全区视电阻率。

在实际工作中, 若已知收发距和工区的平均电阻率, 可根据式(7)估计出进入近区时频率f_N。以f_N作为数据采集的下限频率, 避免频率比f_N低时采集到无用的近区信号和增加测量时间。

图5为理论计算的H型地电模型不同收发距卡尼亚视电阻率及全区视电阻率曲线。当r=300 m和r=600 m时, 卡尼亚视电阻率曲线探测不到埋深400 m的低阻层; 当r=2 km和r=5 km时, 卡尼亚视电阻率曲线可以很好地反映出低阻层的存在, 但对低阻层的下伏高阻地层反映不明确。当r=300 m时, 全区视电阻率虽然对基底反映不明显, 但已经能反映出中间低阻层; 当r=600 m时全区视电阻率反映出中间低阻层的存在, 对下伏地层的高阻属性有反映; 当r=2 km和r=5 km时全区视电阻率较好反映了整个地电断面的情况。可见, 全区视电阻率的探测深度远大于卡尼亚视电阻率的探测深度。

	Figure Option View Download New Window
	图5 同一模型探测深度和收发距的关系

5 应用实例分析

勘探区域位于中国五台山块隆中部, 系舟山掀斜向斜的南西翼。区域内出露地层由老到新有太古界龙华河群均才组; 古生界寒武系下统、中统、上统; 奥陶系下统、中统下马家组及上马家沟组; 石炭系中统本溪组、上统太原组, 二叠系下统山西组; 新生界上第三系、第四系。太古界地层主要为混合花岗岩、斜长角闪岩、黑云母片岩、黑云斜长片麻岩; 寒武系和奥陶系地层以泥质白云岩、灰岩为主; 石炭系和二叠系地层以页岩、砂岩、煤层为主; 新生界以亚砂土、砂及卵砾石为主。

区域内出露的岩浆岩为吕梁晚期苏长辉长岩、辉绿岩, 燕山期花岗岩。吕梁期苏长辉长岩被寒武系、奥陶系地层所覆盖, 呈大型复层状侵入于龙华河群均才组地层中。通过之前的地质、物化探工作, 表明该区辉长苏长岩具有形成钒钛磁铁矿和铜、钴、镍硫化物矿的远景:辉长苏长岩体边缘相细粒苏长岩体的底部和边部含磁黄铁矿、黄铜矿、黄铁矿、方黄铜矿等硫化物和磁铁矿, 局部地段硫化物较为富集。本次勘探的任务是查明辉长苏长岩体中含硫化物矿的细粒苏长岩体的赋存部位及其形态、规模、产状等情况。ZK001资料显示含硫化物矿的细粒苏长岩体与围岩有着明显的电阻率差异(围岩为辉长苏长岩体和太古界混合花岗岩, 均表现为高阻), 故用CSAMT法进行视电阻率解释是可行的。

选用美国最新一代产品GDP32^Ⅱ型电法工作站进行了CSAMT测量, 采用TM模式标量测量方法; 选取收发距r=6 km, 发射极距AB=1 km, 发射方向平行于测线; 工作中使用的最低频率为0.125 Hz, 最高频率为8 192 Hz, 每6个测点测量一个中间点的H_y。

选择该区83线500号测点的测量结果进行计算对比。该点有一钻孔ZK001, 钻孔信息见表2, 电阻率测井曲线见图6a。测井资料显示电阻率断面类型为KH型, 下部的低阻反映了矿体的存在。

表2 钻孔ZK001地质信息

图6b显示, 500号点实测全区视电阻率曲线纵向上表现为低阻— 高阻— 低阻— 高阻变化, 符合ZK001测井结果, 反映出了Cu、Ni矿化层; 卡尼亚视电阻率在波区与全区视电阻率曲线基本重合, 但对测井信息显示的第二个低阻层没有反映, 视电阻率最后一直呈上升趋势, 远大于地层的实际电阻率, 说明了卡尼亚视电阻率的探测深度未达到矿化层。在本次应用中, 卡尼亚视电阻率探测深度约为0.1r, 而全区视电阻率探测深度达到0.5r。

	Figure Option View Download New Window
	图6 500号点全区视电阻率和卡尼亚视电阻率曲线对比

6 结论

(1) 双极源场只有在远区才可以近似看作平面波, 可用趋肤深度作为探测深度, 而在过渡区和近区, 不能以趋肤深度作为实际勘探深度, 还应考虑收发距的影响。

(2) 在保证一定信噪比的前提下, 决定CSAMT探测深度的是频率、收发距和地下介质电阻率的综合作用, 进入近区场, CSAMT法不再具有测深能力。

(3) CSAMT法全区视电阻率能反映出过渡区的地电特征, 但改变不了其在近区不具有测深能力的事实。因此, 就当前的可控源测深理论, 广域电磁法也只有在过渡区和远区有意义, 理论上实现全区探测是有问题的。

(4) 对于均匀半空间模型, 统计得到电磁场进入过渡区时的|kr|为A_T=4.789, 进入近区时的|kr|为A_N=0.106。利用A_T和A_N可得到任意地电模型和收发距组合进入过渡区和近区时对应的频率f_T和f_N。当频率f< f_T时, 卡尼亚视电阻率不具有探测能力, 当频率f< f_N时, 全区视电阻率不具有探测能力; 进而得到卡尼亚视电阻率的最大探测深度约为0.3r, 全区视电阻率的最大探测深度约为3.7r。应用实例中, 卡尼亚视电阻率探测深度为0.1r, 而全区视电阻率的探测深度达到了0.5r。

致谢:在论文的研究及成稿过程中, 得到了长安大学李貅教授、山西地球物理化学勘查院赵斌高级工程师、李建国高级工程师的大力支持, 表示感谢。

The authors have declared that no competing interests exist.

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2004

0.0

底青云, Martyn

Unsworth

, 王妙月. 有限元法2. 5维CSAMT数值模拟[J]. 地球物理学进展, 2004, 19(2): 317-324.

Now most of CSAMT data processing methods are developed in one dimension, that is that supposing the earth media is horizontal layers, this will cause some wrong results for an earth whose conductivity varies in two or three dimensions. For some case's, the survey lines are parallel to the geologic structure's dip direction. In such situation, to consider three dimensions source and two dimensions earth is enough. In order to reasonably Simulate the three dimension source and two dimensions earth, this paper introduces a 2.5D finite element forward model method for CSAMT data, which bases on the Maxwell's equation. The main principle of this forward modeling method is to synthesize data for three dimensional signal source with a series of different wave numbers in geologic structure's strike direction （direction x in Cartesion coordinate system）. One typical three layers model is used for 2.5D forward modeling, Because for such typical model the EM caused with a 3D source has an analytical integral solution, through numerical method, The EM field values is easy to determined. Though comparison with these two methods, the reliability of 2.5D modeling method and software is verified. Then we introduce another model outlined from known geological structure in a coal deposit and compared the results modeled with 2.5D modeling method with the observed real CSAMT data in the field. The comparison shows they consist very well. The comparison results show that the 2.5D forward modeling method and correspond software in this paper provides a good tool for CSAMT data modeling because the finite element method can be used for the models with lateral variation of earth electric properties, it will be useful to model 3D source and 2D earth media.

1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100101,China; 2. Department of Physics, University of Alberta, Edmonton Alberta Canaela T6G 2J1

目前国内大多数CSAMT资料处理都用一维反演方法,即假定地球介质是水平层状地电结构,这对于横向变化较大的介质结构的反演则是不真实的.为了合理的模拟可控信号源的三维特征应该使用三维有限元方法.受计算机内存和计算速度的限制,三维方法的实用化受到约束.在许多情况下,地电结构沿走向变化很小,只沿倾向发生变化.这种地电结构是二维的,而人工源是三维的,因此CSAMT资料的观测可用2.5维有限元方法进行数值模拟.本文从麦克斯韦方程组出发,建立了2.5维有限元CSAMT数值模拟方法,其核心是把地电参数变化小的走向方向转化成波数域,用一系列波数模拟三维源的特征.用一个横向均匀的三层地电结构模型展示了2.5维数值模拟的特征,并和一维模拟结果进行了比较,证实了有限元方法2.5维CSAMT数值模拟的可靠性.在此基础上对一个地电结构已知的实际模型进行了2.5维数值模拟并和该剖面的野外实测剖面数据进行了比较,进一步有效地说明了本文介绍的2.5维CSAMT数值模拟方法是仿真和可靠的,为在此基础上的2.5维反演打下了良好的基础.

2004

0.0

底青云, Martyn

Unsworth

, 王妙月. 复杂介质有限元法2. 5维可控源音频大地电磁法数值模拟[J]. 地球物理学报, 2004, 47(4): 723-730.

This paper discusses deeply the characteristics of EM field for 2D complex earth media. We introduce the characteristics of electric field, magnetic filed and apparent resistivity, and phase produced by a finite electrical dipole source over 100Ωm homogeneous halfspace media. From this result we know the field change behavior over the distance from the transmitter to the receiver, and that we should use a proper transmittingreceiving mode. In wave number domain, the EM field shows that the field of low wave number contributes much more than that of high wave number. And then we demonstrate the CSAMT forward modeling apparent resistivity, phase pseudosetions and frequency curves for twoanomaly bodies, twoleananomaly bodies and down faulted anomaly. Numerical modeling results show directly the anomaly characteristics. This is very helpful for recognizing field data and data inversion and interpretation.

利用有限元2.5维可控源音频大地电磁法（简称CSAMT）数值模拟方法，对100Ωm均匀半空间介质中有限长度的电偶极源产生的电场、磁场及视电阻率、相位特征进行了数值模拟，研究了场的空间变化规律. 在一个象限中，场的特征存在双叶现象，当收发距大于4个趋肤深度时，电阻率较接近介质真实的电阻率，这些结果为观测系统和收发距的选择提供了依据. 波数域场的特征表明，低波数对源的贡献占较大的比例. 有限元法2.5维CSAMT数值模拟的优势在于能较准确地获得复杂介质结构的波场特征. 本文结合直立异常体、倾斜异常体及断陷模型对CSAMT电阻率、相位剖面特征及频率曲线特征的可靠性进行了研究. 数值模拟结果直观地给出了异常体的剖面异常形态. 通过对比研究异常体的剖面异常形态和半空间场的特征进一步说明本文方法和软件在模拟复杂介质结构场特征时是可靠的. 这为认识观测数据，指导反演解释提供了较好的依据.

2006

0.0

王若, 王妙月, 底青云. 频率域线源大地电磁法有限元正演模拟[J]. 地球物理学报, 2006, 49(6): 1858-1866.

The research result of electromagnetic modeling with line source in frequency domain using the finite element method is presented. The first order absorption boundary condition is applied to the outside boundary, which can avoid the error caused by the plane wave assumption. We design two arrays to store the total coefficient matrix with non_zero elements and the corresponding node matrix, respectively, which reduce the consumption of memory. At the same time, the physical meaning is simple and easy to be understood, and it is convenient to find solutions of FEM equations by using the Gauss_Seidel iteration method. The pseudo δ function is used to enhance the stability of solving the equations set. Finally a simple and a complex model are used to test the reliability and effectivity of the method.

本文介绍了频率域线源大地电磁法有限元正演模拟的研究结果. 在外边界上统一应用适合于人工源的一阶吸收边界条件来形成边值问题，可减小基于平面波假设造成的人为截断边界的影响. 程序编辑中设计了两个二维数组分别存储总体系数矩阵的非零元素和在总体结点编号中的位置，使内存占用量减少，且物理意义明确，方便用高斯-赛德尔等迭代法解有限元方程时调用. 采用视δ函数模拟线源，提高了解方程组的稳定性. 最后通过对1个简单模型和1个复杂模型的模拟,证明所用的方法对异常体能够有明显的反映，说明了该方法的可靠性和有效性.

2007

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王若, 王妙月, 卢元林. 三维三分量CSAMT 法有限元正演模拟研究初探[J]. 地球物理学进展, 2007, 22(2): 579-585.

The finite element equation of 3D3C CSAMT electric field is derived from Maxwell equations using Galerkin method. The divergence condition is added forcedly to the electric field boundary value problem after knowing its necessity, which makes the solution correct. Two kinds of technique are extended to 3D CSAMT method modeling, which are used successfully in 2D electromagnetic modeling with line source in frequency domain. One of them is that the first order absorption border condition is applied to the outside boundary, which can avoid the error caused by plane wave assumption and by the artificial boundary of calculation area. The other is about how to store the total coefficient matrix，we design two arrays to store the total coefficient matrix with non-zero elements and the corresponding node matrix respectively, which reduce the consumption of memory, at the same time, whose meaning is simple and easy to be understood, and it is convenient to solve FEM equations set by using iteration method. At last the theory is tested by the response of half homogeneous space model.

首先从麦克斯韦方程出发，用伽里金方法推导了三维三分量CSAMT法的有限元方程.在研究过程中，认识到加入散度条件的必要性，在公式中强加了散度条件，提高了解的完备性.其次将成功应用于二维线源频率域电磁法有限元模拟中的两种技术推广到三维中，一是边界条件统一采用一阶吸收边界，使线源产生的电磁波在边界上按波的传播规律被吸收，以降低平面波假设造成的影响；二是总体系数矩阵的存储，用两个二维数组分别记录总体系数矩阵的非零元素及其在总体结点编号中所处的位置，使总体系数矩阵的存储量达到最小的同时，物理意义明确，迭代求解时迅速简便.最后用均匀半空间模型进行了验证.

2008

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底青云, 王妙月, 王若, 等. 长偶极大功率可控源电磁波响应特征研究[J]. 地球物理学报, 2008, 51(6): 1917-1928.

Generally, the geoelectrical structure of the earth′s crust and upper mantle only is considered in electromagnetic exploration. However, for a long bipole source (approximately several tens kilometers long), the effect of the ionosphere on the electromagnetic (EM) field should be taken into account when observations are carried out at a very remote locations far away from the source (several thousand kilometers). Especially, the configuration which includes the ionosphere, the atmosphere and the earth, called the “earth-ionosphere” case, should be considered. However, there are only a small number of publications related to this problem. In our study, we analyze first the electromagnetic field excited by an electric dipole within the traditional control source electromagnetic (CSEM) configuration using the integral equation method. We consider a three-layer model of the earth-ionosphere media. The modeling results closely match the half-space analytical data, since the effect of the ionosphere for this small scale bipole source is negligible. This confirms that the integral equation method is a reliable and effective method for modeling earth-ionosphere media. We examine the EM fields’ behavior in the model of the complicated earth-ionosphere media with the field excited by a long bipole source in the far-field and wave-guide zones. We model the decaying properties of electromagnetic fields for three-layer earth-ionosphere model considering a 50 km long current bipole source. Due to the influence of the ionosphere, the earth-ionosphere EM fields, excited by a long bipole source, has an extra wave-guide zone, where the field behavior is very different from the far field zone. We also model the EM fields for multi-layer models typical for continental shield and platform with 50 km long bipole and 200 A current source, and for the petroleum reservoir model including the ionosphere layer that is 100 km thick, and an air layer with the same thickness using a bipole that is 50 km in length. The modeling results show that the targets can still be easily identified in the earth-ionosphere EM fields with a very large offset (more than 1000km).

地球物理学中关于电磁波勘探研究通常采用的是地球半空间模型.然而，对于几十公里的有限长电缆源（长偶极源），远距离电磁波场探测必须要考虑电离层的影响，它是一个全空间问题.关于包含电离层、空气层和地球介质（我们称“地-电离层”模式）的电磁波场特征的研究在国外较少，国内几乎是空白.本文采用全空间积分方程法首先对小尺度的可控源电磁波场特征进行了研究，由于此时电离层的影响可忽略，它应该和半空间成熟的CSAMT模拟结果一致，对比结果表明，二者是一致的，验证了全空间模拟方法的可靠性和有效性.随后进行了50 km长电缆电离层和空气层高度都为100 km的“地-电离层”模式大尺度电磁波场模拟，以探讨大尺度可控源电磁波场的特征.给定频率的“地-电离层”模式电磁场的衰减曲线表明长电缆远距离电磁波场由于受电离层的作用存在衰减逐渐变小的过渡场和衰减变小的波导场.为了探讨复杂介质“地-电离层”模式电磁波特征，对“地-电离层”模式的典型地盾和地台多层介质模型进行了数值模拟，得到了偶极源长度50 km、电流200A、收发距离远达1600 km和2500 km的合理的电磁场结果.最后，对一简单含油储层结构模型进行了长偶极、大功率、远距离电磁波场响应计算.储层横向不均匀复杂结构模拟的结果表明，考虑电离层和大气层的“地-电离层”模式大尺度深层复杂介质模拟时，电磁场对深部目标体仍有很好的异常响应.

2014

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张斌, 谭捍东. 带地形的可控源音频大地电磁法二维正演[J]. 物探与化探, 2014, 38(1): 151-156.

In this paper, secondary field algorithm was used to study CSAMT two-dimensional forward problem. Forward modeling used finite-element method, and it employs compressed storage and conjugate gradient technique to accelerate the speed of forward algorithm. In addition, topography was added to the forward algorithm. Finally, the algorithm was tested by means of a synthetic model. The test shows promising results.

利用二次场算法研究了可控源音频大地电磁法二维正演问题。采用有限单元法进行正演模拟，将矩阵压缩存储和共轭梯度解方程方法应用到正演算法中，加快了正演算法的速度，并且将地形因素考虑到正演算法中。通过不同的模型验算，检验了算法的精度。

2015

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王刚, 杨生, 雷达, 等. CSAMT场源效应的三维模拟与试验[J]. 物探与化探, 2015, 39(1): 132-135.

Source effects have serious impact on the application effect of CSAMT. In order to analyze the effect of the source effects, the authors used three-dimensional integral equation numerical simulation method to simulate 3D anomalous body below the source, and then made a field test. Simulations and field tests have proved that, due to the different depths of the bedrocks, only the low band is affected, whereas the high band is almost unaffected, and that the low resistivity body can generate stronger source overprint effects, so the observational data are more remarkably impacted by the low resistivity body.

场源效应严重影响了可控源音频大地电磁法(CSAMT)的应用效果,为了分析场源效应的影响,利用三维积分方程数值模拟计算方法,模拟场源下方存在三维异常体模型,然后做了相关的野外试验.模拟和野外试验证明场源下方基岩深浅不同,受影响的是低频段,高频段几乎不受影响;低阻体产生的场源复印效应更强,也就是说观测数据受低阻体影响更大.

2003

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王若, 王妙月. 可控源音频大地电磁数据的反演方法[J]. 地球物理学进展, 2003, 18(2): 197-202.

This paper is a review on inversion method of controlled source audio-frequency magnetotellurics data. For a horizontally layered earth it was the first time people get the better result from the direct inversion with full wave data than with single plane wave data only. But the method is difficult to apply to 2D and 3D earth medium with complicated electric structures. For the 2D complex earth medium with lateral and vertical variation, Occam inversion method not only consider the lateral smooth function but also the vertical smooth function, the good result of smoothed lateral and vertical electric property can be obtained,but some small features may be smoothed out. Rapid relaxation and conjugate gradients inversion algorithm have advantages of calculation time and computer memory saving. they have frequently been used in 3D inversion. Rapid relaxation method is better in saving calculation time, because it need only solve small set of equations in updating model and only do one forward solution in each inverse iteration, at the same time, the Jacoby matrix is obtained. Because of no analytical solution for complex earth, the numerical calculation is needed in forward solution for the later three methods. The reliability and calculation velocity of forward modeling, affect the efficiency of inversion method, so this is one of research direction of future study in inversion method for 2D,3D complex earth.

从反演方程、构造目标函数和求解三方面对用于可控源音频大地电磁法(CSAMT)的实用反演方法中的四种进行了描述.水平层状地层CSAMT法资料的直接反演法首次尝试了一维空间的全资料CSAMT反演,效果较好,但该方法尚难应用于2D、3D复杂介质中;奥克姆反演方法既考虑了横向的光滑函数,又考虑了纵向的光滑函数,得到比较光滑的横向、纵向变化的背景电性结果,但有可能把一些小构造光滑掉.快速松驰反演算法和共轭梯度算法由于计算速度快,占内存少而被用于三维反演中,二者相比,快速松驰算法在求解雅可比矩阵时只做一次正演计算,在更新模型时解小型方程组,所以在速度上更胜一筹.在后三种算法中,由于复杂电性结构无解析解,正演计算都采用数值计算.数值计算的可靠性、速度影响着反演算法的有效性,这方面的研究也将是2D、3D复杂电性结构反演的研究方向之一.

... 同时伴随着CSAMT法正演的发展,CSAMT法的反演研究也取得了一定的进展^[8,9] ...

2012

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林昌洪, 谭捍东, 舒晴, 等. 可控源音频大地电磁三维共轭梯度反演研究[J]. 地球物理学报, 2012, 55(11): 3829-3839.

CSAMT plays an important role in the field of resource exploration and so on. This work applies the finite difference method to the CSAMT forward modeling. We develop a three-dimensional (3D) conjugate gradient inversion algorithm for inverting CSAMT data using the regularized solution and conjugate gradient inversion method. In the inversion, the computation of Jacobian matrix is replaced by two-time "pseudo-forward" problem solution to make the model updated directly. This algorithm is suitable for inverting CSAMT in the entire field (near field, transition zone and far field) data to obtain 3D geoelectrical structure underground. The synthetic example demonstrates the validity and stability of the 3D conjugate gradient inversion algorithm presented in this paper.

可控源音频大地电磁法在资源勘探等领域中发挥着重要的作用.我们把有限差分数值模拟方法用于可控源音频大地电磁三维正演,结合正则化反演方案和共轭梯度反演的思路,将反演中的雅可比矩阵计算问题转为求解两次"拟正演"问题,得到模型参数的更新步长,形成反演迭代,实现了可控源音频大地电磁三维共轭梯度反演算法.该反演算法可用于对有限长度电偶源激发下采集到的可控源音频大地电磁全区(近区、过渡区和远区)视电阻率和相位资料进行三维反演定量解释,获得地下三维模型的电阻率结构.理论模型合成数据的反演算例验证了所实现的可控源音频大地电磁三维共轭梯度反演算法的有效性和稳定性.

... 同时伴随着CSAMT法正演的发展,CSAMT法的反演研究也取得了一定的进展^[8,9] ...

1996

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吴璐苹, 石昆法, 李荫槐, 等. 可控源音频大地电磁法在地下水勘查中的应用研究[J]. 地球物理学报, 1996, 39(5): 712-717.

Through analyzing a vast amount of data by prospecting the groundwater using CSAMT（controlled source audio magnetic telluric）, we sum up the apparent resistivity y features which show low in the central part and high in the both sides corresponding to the warel-bearing structure.Using this features,we have solved the groundwater prospecting problem in the mountain area and hilly area. The successful rate is very high in well-driving.

根据可控源音频大地电磁（ＣＳＡＭＴ）法进行地下水勘查时取得的大量资料，通过总结、分析与研究，提出了在蓄水构造的断层上，ＣＳＡＭＴ测量的视电阻车断面等值线图呈中间低、两侧高的异常特征．利用这一模式解决了在山区、半山区，很多地球物理方法难以解决的地下水勘查问题．经打井验证，成井率很高．

1996

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于昌明, 石昆法. CSAMT法在四台402盘区陷落柱构造探测中的应用[J]. 地球物理学进展, 1996, 11(2): 137-147.

Controlled Source Audiomagnetotelluric Method （CSAMT） is used to look for fallencolumn of coal fields recently. The study result in No. 402 area of Datong city shows 2 fallen columns found by CSAMT method. In this paper, we also get some characteristics of electrical resistivity of these fallen columns in coal field. The distribution regularity of electrical resistivity features in transverse and vertical directions have been summarized. Research result has shown possibility of CSAMT method applied to fallen columns of coal-fields.

可控源音频大地电磁法（ＣＳＡＭＴ法）应用于寻找煤田陷落柱构造，乃是个新课题。通过对大同矿务局四台矿４０２盘区的野外实际应用，发现了两个陷柱落构造，与实际资料基本吻合。在获得可靠的实际资料之后，本文进一步研究了陷落柱的电性特征，总结陷落柱在垂向及横向上的电性分布规律，试图建立本地区运用ＣＳＡＭＴ法寻找陷落柱的地球物理基本模式。实验结果表明，该法应用于寻找陷落柱构造是可行的。

1998

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于昌明. CSAMT方法在寻找隐伏金矿中的应用[J]. 地球物理学报, 1998, 41(1): 133-138.

Controlled Source Audiomagnetotelluric method is one of the geophysical methods applied in Beilidian region. Because penetration coefficient and resolution power of induced polarization method （IP） is correlative with geometric factors, so the deeper geology features can not been obtained clearly by IP method. CSAMT is a better way to solve mis problem. First area survey by IP method was carried out according to the regional geology background, mineralization conditions and physical features of rocks in mine field, then CSAMT method was measured. After data processing, two low-resistivity gradient zones in deeper part of measure area can be found; one of them inclined steeply and another one inclined slowly. They intersect in 800m depth.We believe that they are main host structure and ore-control strictires.

可控源音频大地电磁法（CSAMT）的应用是百里店矿山多种地球物理研究的一部分．由于激发极化法（IP）的穿透率和分辨率是与几何因素密切相关，对于较深部的地质特征，靠IP法不容易分辨出来．CSAMT较好地解决了这个问题，首先，根据区域地质背景、成矿条件和矿区岩石物性特征，开展了面积性的激电测量，进而开展了CSAMT方法的探测研究．通过对CSAMT原始数据的分析解释，发现测区深部存在两条低电阻率梯级带，其中一条为陡倾斜；另一条为缓倾斜，两者在地下800m左右深度处相互斜交．经地质推断解释认为：这是测区内金矿的主要控矿、导矿及容矿构造．

2001

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底青云, 石昆法, 王妙月, 等. CSAMT法和高密度电法探测地下水资源[J]. 地球物理学进展, 2001, 16(3): 53-57.

China, even the world, is facing the shortage of water resources. Reasonable to exploring and using water resources shows us that the situation is hard. And it is also the key problem of economic development and our wealth. The paper introduces CASMT method and high-density electric resistivity method, which is developed in recent years, and shows some applied examples for the two methods. The results tell us the two methods in this paper are the effective tools for water resources exploration.

我国乃至世界目前都面临着严重的水资源的短缺,利用新技术、新方法合理勘探开发并利用水资源,是经济腾飞的

2002

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底青云, 王妙月, 石昆法, 等. V6多功能系统及其在CSAMT勘查应用中的效果[J]. 地球物理学进展, 2002, 17(4): 663-670.

Ruggtdized multifunction V6 system was introduced by Institute of Geology and Geophysics, Chinese Academy of Sciences from Canada Phoenix Geophysics Limited in 2000. It is one of the most powerful instruments for controlled source audio-frequency magneto-telluric exploration. It has 62 frequency series, Strong transmittal power and strong ability of anti-noise （anti-interference）. It also has fast 512kHz 16-bit ADC plus minimum 8 gain bits for controlled source. The transmitter and recever are synchronized with GPS. These feature makes it has advantage of monitoring much weak effective with high vertical and horizontal resolution and high ratio of signal noise. Hence it can be used to make high precise exploration. Case studies in standart geological profile near Niulanshan water power station and in Laiwu iron mine shandon province with V6 system show that V6 system can carectly determin the depth of objective layer and the distribution and structures of water bearing stratum.

Institute of Geology and Geophysics,Chinese Academy of Sciences, Beijing 100101, China

地球物理多功能探测系统V6是中国科学院地质与地球物理所2000年底从加拿大凤凰公司引进的新仪器,它具有频点多(62频点系列),抗干扰能力强,发射功率大,A/D转换16位及发射与接收信号GPS(Globe Position System)时钟同步等特点,能有效地提高纵向分辨率和测量信号的信噪比,为浅层精细勘探提供了保障.V6系统在牛栏山水源八厂标准剖面的试验,山东莱芜业庄矿突水勘查工作等充分证明,V6系统能较准确地确定目的层深度,结合地质资料,可以提供含水性的判断.

2005

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李志华. 某新建铁路复杂长隧道岩层地质与CSAMT 特征[J]. 地球物理学报, 2005, 20(4): 1190-1195.

This paper analyses the advantages and disadvantages of many geophysical exploration methods which are used in long complex railway tunnel, and points out that CSAMT (Control Source Audio\|frequency Magnetotelluric Method) is a powerful exploration method of applied geophysics for deeper and complex geology structure exploration. The paper shows some successful examples of CSAMT survey in the area studied. The resistivity anomalies for the typical geology layer of gypsum breccia in this railway tunnel are particularly analyzed, and the integrated interpretation results for CSAMT survey conducted for the tunnel is illustrated.

分析了多种地球物理勘探方法在复杂长隧道探测中的优缺点，指出了CSAMT（可控源音频大地电磁）法在工作条件极其困难，地形复杂，交通不便，要求勘探深度大的隧洞勘察中，是一种行之有效的物探手段.以较高的显示度列举了CSAMT法在本区探测成功的实例.就隧道主要特殊岩层膏溶角砾岩的地球物理异常特征进行了详尽分析，给出了CSAMT法在本区隧道结构面综合地质解释结果.

2005

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孙英勋. CSAMT法在高速公路长大深埋隧道勘察中的应用研究[J]. 地球物理学进展, 2005, 20(4): 1184-1189.

CSAMT system is of electromagnetic auto collecting and analysis system comprises advantages of MT and AMT. The Paper discusses the principle, characteristics, working methodology and data analysis of CSAMT based on the case study of its application in survey and investigation of the deeply-buried long tunnel in Expressway in Yunnan. CSAMT successfully interprets the location of soft and weak layer, underground water and broken fractures with assistance of other technical method, which provides good rationale for the classifying of surrounding rocks of the tunnel acting as a new and the first methodology for survey and investigation for deeply-buried long highway tunnels.

CSAMT法是一套综合了MT和AMT各自优点的电磁自动采集和处理系统.本文介绍了CSAMT的原理、特点、工作方法和资料处理.该系统首次运用于高速公路长大深埋隧道勘察中，结合其它手段，成功解译出了隧道的软弱层、地下水及断层破碎带的位置，为划分隧道围岩类别提供了较好的依据，同时也为高速公路长大深埋隧道提供了一种新的勘察方法.

2007

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谭儒蛟, 胡瑞林, 徐文杰, 等. 金沙江龙蟠变形体隐伏构造CSAMT 探测与解译[J]. 地球物理学进展, 2007, 22(1): 283-288.

Longpan deformation slope lies at the right bank of the strath in Jinsha River. The areal geology tectonics here belongs to the Zhongdian-Longpan-Qiaohou faults belt region, the tectonic structures in this area are complicated and blurry. In order to get to the bottom of the tectonics, multifunctional V6A system in CSAMT method is applied. Case studies in this area show that CSAMT method with V6A system is an effective approach to explore perdue faults under quaternary stratum in high mountains and steep gorge area. By interpretation the CSAMT and engineering-geology exploration information synthetically, the tectonic pattern of Longpan area is put forward for the first time in this paper, and the conclusion is the base of analyzing the stability of Longpan deformation slope.

龙蟠变形（岩）体位于金沙江宽谷河段右岸，规模巨大.此处区域主构造线为近SN向的中甸－龙蟠－乔后断裂带，地质构造背景极其复杂.为查清变形体内的隐伏构造，本次运用V6A多功能系统展开了CSAMT法探测研究.通过对CSAMT反演电阻率断面和钻孔、平洞等所获取的工程地质信息的综合解译分析，检验了CSAMT（V6A系统）法在高山峡谷区隐伏构造探测中的有效性和可靠性，解译成果全面清晰地揭示了冲江河断裂等在金沙江宽谷河段的展布格局，同时为龙蟠变形体稳定性评价提供了关键性地质资料.

2008

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成江明. 可控源音频大地电磁法在隐伏煤矿区的应用[J]. 地球物理学进展, 2008, 23(4): 1269-1272.

应用可控源音频大地电磁法在福建隐伏煤矿区进行了勘探研究.针对“三下找煤”,在试验区做了CSAMT探测,分析原始数据,结合各矿区相关的地质资料,比对反演结果,进行了地层划分,圈定了靶区.研究结果表明,在隐伏煤矿区应用CSAMT法探测煤系地层切实可行。

2008

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李帝铨, 底青云, 王光杰, 等. CSAMT 探测断层在北京新区规划中的应用[J]. 地球物理学进展, 2008, 23(6): 1963-1969.

In order to provide basic geological information for a new planning district in Beijing, it is necessary to identify the precise location of the faults, the thickness of the overburden, and estimate the activity of the faults. We used CSAMT method for survey work. As there was strong electromagnetic interference in the survey area, we took many means to ensure the data obtained credible. By employing genetic algorithms full data inversion program for data inverse, we achieved a good result. With comprehensive analysis of the geophysics and geological data, we have determined the precise locations of faults, and provided reliable information for the new district planning.

为了给规划中的北京市某新区提供基础地质资料，需查明区内断裂的准确位置、产状以及覆盖层厚度.利用CSAMT方法进行了勘察工作，由于区内人文干扰和电磁干扰严重，野外施工时采用了多种手段以保证观测数据的可信度；数据处理时利用作者开发的基于遗传算法的CSAMT全资料反演程序对野外数据进行反演.分析反演结果并结合已知地质资料，给出了区内断裂的准确位置等信息.为新区规划提供了可靠的基础资料.

2013

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王绪本, 陈进超, 郭全仕, 等. 沁水盆地北部煤层气富集区CSAMT勘探试验研究[J]. 地球物理学报, 2013, 56(12): 4310-4323.

On the basis of the analysis of the relationship between the coalbed methane (CBM) enrichment region and groundwater and geological structure in the north Qinshui basin, the magnetotelluric method was employed to detect underground water distribution as well as the favorable and unfavorable geological factors which pose impact on coalbed methane enrichment, and indirect detection of the CBM relative enrichment region. According to the CBM enrichment geological model and designed the geophysical model, using the finite element method to carry out the forward modeling, this work discussed the feasibility of the detection mode, based on which we selected the north Qinshui basin CBM exploration area to carry out the controlled source audio magnetotelluric (CSAMT) technological experiment. Coupled with the geological, drilling and logging data, we have completed the experiment data processing and interpretation. The results show that the use of CSAMT method can effectively obtain electrical structure of strata, infer water content, and water-rich areas. Combining with the favorable enrichment CBM geological conditions and influencing factors, it is possible to achieve indirect prediction of the favorable CBM enrichment region.

在分析沁水盆地北部煤层气富集与地下水和地质构造之间的关系基础上，采用大地电磁法探测地下水分布以及有利和不利煤层气富集影响因素、间接探测煤层气相对富集区；根据煤层气富集地质模型设计了地球物理模型，利用有限单元法开展典型薄层模型正演模拟，讨论了探测方法的可行性；选择山西沁水盆地北部煤层气勘探区开展可控源音频大地电磁探测技术试验，结合已有地质、钻井及测井资料完成了试验资料的处理与解释；试验结果表明，利用可控源音频大地电磁法能有效获得地层电性结构，推断含水、富水区，结合煤层气有利富集地质条件和影响因素，可以实现间接预测煤层气的有利富集区.

2014

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黄高元, 张国鸿. CSAMT法张量与标量测量在已知铁矿区上的对比试验[J]. 物探与化探, 2014, 38(6): 1207-1211.

Tensor measurement and scalar measurement of the CSAMT method were conducted in two known iron ore districts of Anhui Province, and a comparison of the application results was made along the known geological exploration section. The results of the test show that, under the condition of 1-D layered electrical property structure, the ore-prospecting result of the tensor measurement is close to that of the scalar measurement, whereas under the condition of complex electrical property structure, the ore-prospecting result of the tensor measurement is better than that of the scalar measurement. Some problems which require further investigation in the tensor measurement of the CSAMT method are also discussed in this paper.

在安徽省两个已知磁铁矿区上进行了可控源音频大地电磁法(CSAMT)张量测量与标量测量的对比试验,根据已知地质勘探剖面进行了应用效果的对比工作。试验结果表明,在一维层状电性结构条件下,张量测量与标量测量的找矿效果相近;在电性结构复杂情况下,张量测量的找矿效果优于标量测量结果。同时,指出可CSAMT法张量测量工作需进一步探讨和亟待研究的一些问题。

2014

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张作宏, 王军成, 戴康明. CSAMT 在沿海围垦区地热勘查中的应用[J]. 物探与化探, 2014, 38(4): 680-683.

Rudong area is rich in saline water characterized by low resistivity, so it is difficult to use tradition DC electrical methods in deep regional survey. V8 has high-power and CSAMT has strong penetrating capability, so they can improve the resolution when the density of frequency increases. In combination with the data of geology and geophysical prospecting, we can infer the structure of heat source water in low-resistivity covers. The results obtained by the authors show that the structure is a good tunnel for heat source. The possibility of the application of the method to the extremely low resistance cover is also discussed in this paper.

江苏省如东某沿海围垦区富含咸水，电阻率值极低，传统直流电法难以开展深部勘查工作。利用V8功率大、CSAMT法穿透力强的优点，通过加密频点等方法技术提高分辨率，结合已有地质、物探资料推测了低阻覆盖层下的控热储水构造，验证结果表明所推断裂构造是沟通深部热源的有利通道，验证了该方法应用于超低阻覆盖区的可能性。

2014

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陆桂福, 刘瑞德. 大功率激电和CSAMT 在隐伏矿产勘查中的应用[J]. 物探与化探, 2014, 38(5): 921-924.

The exploration of deep concealed ore deposits is the main task at present. A lot of electrical measurements have been completed in Xilin Gol League of Inner Mongolia in recent years, which mainly consist of high-power IP and CSAMT or their combinational methods, with good prospecting results achieved. High-power IP measurement was used for discovery and delineation of mineralization limits and distribution of structures in the ore district; Inversion of resistivity of CSAMT section was conducted to deduce underground electrical characteristics of lithology, geological structure, attitude of structure, and size and space of ore (mineralized) body. The results achieved by the authors provide the basis for the drilling. This paper describes the exploration process of a certain deep concealed lead-zinc deposit in Inner Mongolia and makes interpretation.

隐伏矿产勘查是我国现今的主要任务，近几年在内蒙古锡盟地区做了大量的电法测量工作，主要应用大功率激电和可控源音频大地电磁测深方法组合进行找矿，取得了很好的找矿效果。在内蒙古某深部隐伏铅锌矿的勘查中，将大功率激电法用于快速发现和圈定矿区矿化范围及构造展布情况，用可控源音频大地电磁测深法反演电阻率断面图推测地下岩性电性特征、地质结构、构造产状、规模和矿（化）体的赋存空间，为钻探工程提供依据。

2010

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何继善. 广域电磁测深法研究[J]. 中南大学学报, 2010, 41(3): 1065-1072.

根据水平电流场源和垂直磁场源在半均匀空间地面的电磁场解析表达式,定义了广域视电阻率,建立1种新的频率域测深方法即广域电磁测深法.研究结果表明:采用广域电磁测深法可以在过渡带进行测量,即以较小的收发距探测到较大的深度;广域电磁法包括E-Ex广域电磁测深和E-Ez广域电磁测深等方式,每种方式各有其特点,而且都只测量1种物理量;广域电磁法与2n序列伪随机电法相结合还可以发展成2n序列伪随机信号-广域电磁法,不但探测深度大,而且效率高,广域电磁法可用于寻找火山岩油气藏、深部金属矿和工程电法勘探.

... 何继善^[24]在CSAMT法的基础上提出了广域电磁测深法,使得CSAMT法观测范围不拘泥于波区,扩大了测量范围 ...

... 但对于CSAMT法的探测深度,普遍依赖于趋肤深度计算公式^[24] ...

2012

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... 陈明生提出人工源频率域电磁测深的探测深度还受收发距的影响,不能沿用原有的趋肤深度计算公式^[25] ...

... Kρ/f,K包含了收发距的影响^[25] ...

1994

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殷长春. 可控源音频磁大地电流法一维正演及精度评价[J]. 长春地质学院学报, 1994, 24(4): 438-453.

研究发现，两种目前比较常用的可控源音频磁大地电流法（ＣＳＡＭＴ）的正演计算方法，即简化积分法和二次插值法之间计算结果差异较大。为了正确地评价这两种方法的计算精度，本文提出了利用直接积分进行，ＣＳＡＭＴ一维正演的算法，即通过将任意角度频率测深正演结果沿发射源方向直接进行数值积分，得到有限长度发射源的ＣＳＡＭＴ正演结果，大量计算和精度评价发现，在这些算法中，简化积分法和本文提出的直接积分法计算结果吻合

... 2 水平电偶极子均匀半空间E_x、H_y特征CSAMT法发射源是双极源,要通过对电偶极子场沿双极源的长度方向进行积分来获得双极源场^[26] ...

1994

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汤井田, 何继善. 水平电偶源频率测深中全区视电阻率定义的新方法[J]. 地球物理学报, 1994, 37(4): 543-551.

The definition of effective resistivity and its algorithms In horizontal electric dipole frequency electromagnetic soundings are discussed on the basis of the unity of electromagnetic field. Theoretical analysis shows that the effective resistivity improves the curves pattern of the wave-zone apparent resistivity significantly, So it can correct the so called non-plane-wave effect well in frequency electromagnetic soundings, and can indicate the changes of electric sections.A great deal of its application shows that the effective resistivity Possesses reasonable characteristics and goodp rospects of application.

从电磁场的统一性出发，分析了水平电偶源频率测深中等效电阻率的算法原理和具体定义．分析表明，等效电阻率可明显地改善波区视电阻率在非波区场的畸变，较为形象、直观地反映出地电断面的电性变化．数值计算、三维模型计算和实际数据处理表明，等效电阻率具有良好的特性和应用前景．

... 双极源依然沿用远区条件下电磁波阻抗定义的卡尼亚视电阻率,而全区视电阻率的计算则是利用均匀半空间场表达式不断迭代计算得到^[27,28],因此,全区视电阻率和电磁场的性质最接近,但其对地层电阻率特征的反映比电磁场更明显、更直观 ...

2012

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王国顺, 熊彬. 广域视电阻率的数值计算方法[J]. 物探化探计算技术, 2012, 34(4): 380-383.

广域视电阻率与卡尼亚视电阻率相比,能更好地表征地下介质的电性变化规律,一般常使用迭代法和逆插值法求解,这里使用这两种算法对E-Ex方式广域视电阻率进行了计算。结果表明,使用这两种算法所得广域视电阻率,都正确反映了地下介质的电性变化规律,逆插值的影响因素较少,计算过程稳定。其不足之处在于要求插值目标函数单调,迭代法步骤简单,并存在迭代发散的情况。在实际应用时,可根据广域视电阻率公式的特点,选择适当的方法进行计算。