多种物化探手段在断裂勘探中的综合应用   总被引：3，自引：0，他引：3  

刘焕喜  何强  杨涛 《陕西地质》2002,20(1):66-71

结合工程实例分析了工程中较为常用的物化探手段(电测深法、甚低频电磁法和断层气测试法)在断裂勘探中的优势和缺点,提出工程中应用多种物化探手段,才能达到工程目的,获得理想效果。  相似文献   

Features of discrete VLF emissions observed at Gulmarg,India during the magnetic storm of 6–7 March, 1986     

R. Singh  A. K. Singh  D. Siingh  R. P. Singh 《Journal of Earth System Science》2007,116(6):553-559

During the analysis of archived VLF data from Indian low latitude ground stations, some discrete VLF emissions recorded at the low latitude ground station Gulmarg (geomagnetic latitude 24°26′N; geomagnetic longitude 147°09′E, L = 1.28) during moderate magnetic storm activity (Σ K _P ⁻ = 32, K _P index varies from 4 to 6 during the observation period) on 6/7 March, 1986 are presented in this paper. The dynamic spectra of these discrete VLF emissions were observed along with tweeks and its harmonics, which is interesting and complex to explain. In most of the events the harmonic frequency of tweeks correlates with the starting frequency of harmonics of discrete emissions. In order to explain the observed features of discrete VLF emissions, we propose cyclotron resonance interaction between whistler mode wave and energetic electrons of inner radiation belt as possible generation mechanism. An attempt is also made to determine parallel energy, anisotropy and wave growth relevant to the generation process of VLF emissions.  相似文献   

Hydrogeological investigation in Santiago Island (Cabo Verde) using magnetotellurics and VLF methods   总被引：2，自引：0，他引：2  

Fernando A. Monteiro Santos  Eugnio P. Almeida  Mota Gomes  Antnio Pina 《Journal of African Earth Sciences》2006,45(4-5):421-430

A geoelectromagnetic research was carried out in the Santa Cruz region (Santiago Island, Cabo Verde) during June 2004. The survey comprised MT soundings and VLF profiles. The main purpose of the MT profile, carried out across three important valleys associated with freshwater aquifers, was to study the tectonic structures correlated to seawater infiltration. The VLF method was used inside of the valleys for investigating shallow structures related to the aquifer contamination by seawater.Numerical modelling shows that the ocean effect is not important for MT data collected at periods shorter than 1 s. The MT data were inverted using a two-dimensional approach, to obtain the sub-superficial electrical conductivity distribution. The VLF data were processed applying the Karous–Hjelt filters to obtain the equivalent current distribution and inverted using 2-D approach. The results obtained in one of the most important valleys show anomalous current concentration/low resistivity (<20 Ω m) areas at depths greater than 40 m that may correspond to an increase in seawater content.The MT data modelling show that the deep zones beneath the valley are strongly fractured representing good pathways for seawater circulation. The depth of the conductive zones increases from south to north, suggesting a northward decreasing of the seawater infiltration effect. This observation correlates very well with in situ geochemical observations.  相似文献   

东西传播路径上JJI台站甚低频信号的日出效应研究     

王市委  倪彬彬  顾旭东  林仁桐  李光剑  罗凡  彭锐  陈欢 《地球物理学报》2022,65(1):145-156

甚低频(VLF, Very Low Frequency)波的频率范围为3~30 kHz,因其在地球-电离层波导中传播损耗小、传输距离远而被用于低电离层遥测的相关研究.本文基于武汉大学自主研发的甚低频探测系统在湖北随州(31.57°N,113.32°E)的观测数据,详细研究了中纬度地区来自日本JJI(32.04°N,130.81°E)甚低频台站信号沿东西方向传播的日出效应.在对日出期间接收信号的幅度极小值进行统计分析后发现,幅度极小值出现时间的分布与随州或JJI日出时间的变化趋势基本一致.日出期间JJI信号的幅度响应主要包括type Ⅰ和type Ⅱ两种结构,分别对应2个幅度极小值和3个幅度极小值的情况.其中,type Ⅰ结构主要发生在春夏两季,幅度极小值出现的平均时间落后随州日出时间24 min左右;type Ⅱ结构主要发生在秋冬两季.基于波模干涉理论对日出期间两种不同模式的JJI甚低频信号进行模拟研究,结果表明,在JJI-随州的东西向传播路径上,若只考虑前两阶模的影响,模拟结果与观测结果差异明显;若考虑前三阶模的影响,那么模拟结果与观测结果基本一致.由此可见,JJI甚低频信号在短路径上传播时高阶模会对信号的传播产生较大的影响,分析此类路径上甚低频台站信号的传播特征时需要考虑前三阶模甚至更高阶模的作用.  相似文献   

JJI甚低频台站信号对太阳耀斑事件的响应特性   总被引：1，自引：0，他引：1  

顾旭东  罗凡  彭锐  李光剑  陈欢  王市委  易娟  李志鹏  倪彬彬  赵正予  王琛  袁丁 《地球物理学报》2021,64(5):1508-1517

太阳耀斑发生时,日地空间的X射线通量会随之增大,进而影响到地球电离层的电子密度分布,导致地球-电离层波导状态发生改变,因此接收到的甚低频(VLF,Very Low Frequency)信号会表现出对应的扰动现象.2017年9月8日,位于湖北省内武汉和随州两站点的VLF接收机分别监测到与X射线太阳耀斑相关的来自日本宫崎县(130°49′E,32°04′N)的JJI甚低频台站信号(22.2 kHz)的振幅异常事件.分析当日的数据发现JJI信号的振幅对不同的太阳耀斑出现不同的响应类型,而且对于同一个耀斑,两地的信号响应类型不尽相同.通过统计2017—2019年间与太阳耀斑相关的JJI信号振幅扰动事件,发现两接收站点的JJI信号响应类型都与耀斑强度及其发生时间存在一定的关系,且呈现出四种响应类型,即两次上升下降型、先上升后下降型、下降型和上升型,但是四种响应类型的事件占比不同.拟合结果表明信号的扰动幅度与X射线通量的积分成正相关,但是两站点的线性拟合斜率存在差异.JJI信号到武汉和随州均属于近似沿纬度方向的短距离传播,且两接收站点相距较近,因此两传播路径大致相似.研究两路径上JJI信号对太阳耀斑响应的差异性有助于理解VLF信号的传播以及探索其在太阳活动监测方面的应用.  相似文献   

2009年7月22日日食期间VLF信号相位和场强的观测和分析     

张世田  陈林如  王元新 《时间频率学报》2011,34(1)

2009年7月22日日食期间,分别在重庆、桂林和青岛利用阿尔法场强与相位监测仪观测了来自俄罗斯阿尔法导航系统位于Novosibirsk、Krasnodar和Khabarovsk的3个发射台3个频率的甚低频信号,并对实验数据进行了分析。通过建立日食期间的电离层模型,结合实际传播路径地面电磁参数,推测全食区低电离层的等效高度;给出经不同路径传播的VLF(甚低频)信号相位突变与日食发生时刻的关系及原因;分析了日食期间经不同路径传播的VLF信号的场强起伏变化,发现场强变化滞后于相位变化这一现象。  相似文献   

智利地震前DEMETER卫星对空间高能粒子的观测   总被引：2，自引：1，他引：1       下载免费PDF全文

张振霞  李新乔  吴书贵  马宇蒨  申旭辉  陈化然  王平  游新兆  袁亚红 《地球物理学报》2012,55(5):1581-1590

在地震的孕育或发生期间,地球内部岩石圈的活动可能会发出电磁辐射,引起空间电磁扰动,并通过波粒相互作用引起高能电子的投掷角散射,导致高能电子的沉降.本文基于法国DEMETER卫星的观测数据,研究了智利周围区域在智利地震期间空间高能电子的通量、能谱的分布及演化,发现在智利地震发生前第11天和12天,在以震中为中心,经度跨度10°,在DEMETER卫星轨道高度上L跨度0.1的区域内,有超出背景4到6倍的高能带电粒子暴的出现,期间在其北半球磁镜像区域也观测到了显著的电子通量涨高.粒子暴对应的能谱与2010年前三个月的平均能谱存在较大差异.同时观测到在出现粒子暴的两条轨道上VLF(Very Low Frequency,甚低频)电场频谱分别在300 Hz以下以及13~20 kHz的频段存在显著增强,此扰动在时间和地理位置上与高能粒子暴是一致的.基于回旋共振耦合作用的准线性扩散理论,本文对所观测事例的电子能量与电磁场扰动频率做了分析计算.观测数据和理论计算有较好的一致性,表明该粒子暴源自ICE(Instrument Champ Electrique,电磁探测器)观测到的空间电磁扰动,这是典型的空间波粒耦合事例.进一步分析排除了可能引起粒子暴和VLF电场扰动的环境因素,本文认为本次粒子暴和电场扰动的观测可能与智利地震的震前地壳活动存在一定关联.  相似文献   

用VLF、EH4和CSAMT方法寻找隐伏矿--以赤峰柴胡栏子金矿床为例   总被引：34，自引：9，他引：25  

刘红涛  杨秀瑛  于昌明  叶杰  刘建明  曾庆栋  石昆法 《地球物理学进展》2004,19(2):276-285

VLF、EH4和CSAMT均为基于电磁原理的地球物理手段,但它们在探测深度、测量精度和野外操作的复杂程度上有较大的差异.因而不同探测目标和精度要求,尽可能使用不同的方法或方法组合.VLF一般用于矿区及外围的地球物理扫面,以快速确定和发现覆盖层(不超过50～60 m)之下矿化构造系统的空间展布和基本规模.CSAMT具有探测深度大(＞2000m)、工作效率高和抗干扰能力强等特点,一般用于确定矿化系统的深部的宏观几何形态和产状变化.EH4是这三种方法中对地下地质结构解析度最高、有效探测深度适中(800～1 200m)的一种地球物理测深方法,它可以解析较为精确地探测矿体的三维形态、规模、产状变化和细部结构但采集数据时对近场电磁干扰要求较高.这三种地球物理方法在赤峰柴胡栏子金矿区的联合应用,为寻找覆盖层之下隐伏矿体取得了良好的效果.  相似文献   

电离层ELF/VLF电磁波激发研究          下载免费PDF全文

曹丙霞  周志权  乔晓林 《地球物理学进展》2010,25(3)

调制电离层激发ELF/VLF电磁波为深海潜艇通信提供了一种可能的天线产生方式.本文介绍了国外电离层ELF/VLF电磁波激发理论的研究情况和实验结果,引进了HF电磁波加热电离层理论和物理模型并介绍了相应的实验结果,讨论了加热系统的激发效率提高问题.展望了该领域的未来研究方向,并提出了在我国的地理条件下激发电离层ELF/VLF电磁波需要解决的问题.  相似文献   

Fast imaging of subsurface conductors using very low‐frequency electromagnetic data          下载免费PDF全文

Anand Singh  S.P. Sharma 《Geophysical Prospecting》2015,63(6):1355-1370

The study presents a fast imaging technique for the very low‐frequency data interpretation. First, an analytical expression was derived to compute the vertical component of the magnetic field at any point on the Earth's surface for a given current density distribution in a rectangular block on the subsurface. Current density is considered as exponentially decreasing with depth, according to the skin depth rule in a particular block. Subsequently, the vertical component of the magnetic field due to the entire subsurface was computed as the sum of the vertical component of the magnetic field due to an individual block. Since the vertical component of the magnetic field is proportional to the real part of very low‐frequency anomaly, an inversion program was developed for imaging of the subsurface conductors using the real very low‐frequency anomaly in terms of apparent current density distribution in the subsurface. Imaging results from the presented formulation were compared with other imaging techniques in terms of apparent current density and resistivity distribution using a standard numerical forward modelling and inversion technique. Efficacy of the developed approach was demonstrated for the interpretation of synthetic and field very low‐frequency data. The presented imaging technique shows improvement with respect to the filtering approaches in depicting subsurface conductors. Further, results obtained using the presented approach are closer to the results of rigorous resistivity inversion. Since the presented approach uses only the real anomaly, which is not sensitive to very small isolated near‐surface conducting features, it depicts prominent conducting features in the subsurface.  相似文献