裸露岩溶区地下河管道综合地球物理方法探测研究     

陈玉玲  甘伏平  卢呈杰  韦吉益  赵伟 《地球物理学进展》2013,28(3)

本文选取桂林市海洋乡裸露岩溶区地下河管道分别进行了可控源音频大地电磁法、三极电测深法和充电法试验对比研究,其综合成果得到了钻探验证.试验研究表明,充电法对具有出口、进口或天窗的地下暗河定位追踪准确,效果明显.可控源音频大地电磁法探测深度大,横向分辨率高,对寻找深部构造破碎带具有独特的优势.三极测电深法受场地条件、高阻围岩和地形起伏影响较大,不能满足对地下暗河的定位要求.  相似文献   

华南东南沿海地区岩石圈电性结构   总被引：7，自引：0，他引：7  

刘国兴  韩凯  韩江涛 《吉林大学学报(地球科学版)》2012,42(2):536-544

为了研究华南东南沿海地区的壳幔电性结构及其动力学背景,布设了4条大地电磁测深剖面,获得了相应的二维地电模型,并结合相关地质和地球化学信息对地电模型进行了研究。结果表明:研究区西部地壳由于碰撞汇聚作用变厚,东部地壳由于太平洋板块的俯冲作用剧烈减薄。华南东南沿海地区的岩石圈并不是简单的呈现"西厚东薄"的特征,研究区东西两端岩石圈厚度超过100km,推测西段岩石圈增厚主要形成于陆内挤压造山或陆内碰撞汇聚造山作用,而东端岩石圈增厚可能由于大洋板块俯冲时洋壳残留物叠置在岩石圈的下部所形成,而中部岩石圈的减薄与软流圈物质上侵有关,造成此区域大规模软流圈物质上侵的动力来自于太平洋板块俯冲产生的深部热扰动。  相似文献   

Structural controls on the 1998 volcanic unrest at Iwate volcano: Relationship between a shallow, electrically resistive body and the possible ascent route of magmatic fluid     

Koki Aizawa  Yasuo Ogawa  Masaaki Mishina  Kosuke Takahashi  Shintaro Nagaoka  Nobumasa Takagi  Shin'ya Sakanaka  Takuya Miura   《Journal of Volcanology and Geothermal Research》2009,187(1-2):131-139

Magnetotelluric (MT) measurements were conducted at Iwate volcano, across the entirety of the mountain, in 1997, 1999, 2003, 2006, and 2007. The survey line was 18 km in length and oriented E–W, comprising 38 measurements sites. Following 2D inversion, we obtained the resistivity structure to a depth of 4 km. The surface resistive layer (~ several hundreds of meters thick) is underlain by extensive highly conductive zones. Based on drilling data, the bottom of the highly conductive zone is interpreted to represent the 200 °C isotherm, below which (i.e., at higher temperatures) conductive clay minerals (smectite) are rare. The high conductivity is therefore mainly attributed to the presence of hydrothermally altered clay. The focus of this study is a resistive body beneath the Onigajo (West-Iwate) caldera at depths of 0.5–3 km. This body appears to have impeded magmatic fluid ascent during the 1998 volcanic unrest, as inferred from geodetic data. Both tectonic and low-frequency earthquakes are sparsely distributed throughout this resistive body. We interpret this resistive body as a zone of old, solidified intrusive magma with temperatures in excess of 200 °C. Given that a similar relationship between a resistive body and subsurface volcanic activity has been suggested for Asama volcano, structural controls on subsurface magmatic fluid movement may be a common phenomenon at shallow levels beneath volcanoes.  相似文献   

龙门山断裂带西南端地壳电性结构   总被引：2，自引：0，他引：2       下载免费PDF全文

王立凤  赵国泽  詹艳  陈小斌  肖骑彬  赵凌强  王继军  乔亮  韩冰 《地震地质》2014,36(2):302-311

在龙门山断裂带中段于2008年5月12日发生了汶川M_S 8.0地震,5a之后于2013年4月20日在其西南侧即龙门山断裂带SW段发生了芦山M_S 7.0地震。而在汶川地震前,沿龙门山断裂带主体部分存在7a间未发生4.0级以上地震的相对平静期。因此,汶川地震后人们研究了龙门山断裂带的地壳结构及其与汶川地震的成因关系,仅仅相隔5a时间,就在龙门山断裂带的SW段发生了芦山地震,其深部结构和孕震环境以及与汶川地震的关系又成为人们关注的热点科学问题。为了研究龙门山断裂带西南端附近的地壳结构,布置了一条穿越龙门山断裂带西南端附近的大地电磁探测剖面LS6,该剖面位于芦山地震破裂带的西南端。通过采用先进技术对大地电磁数据的分析和二维反演,发现LS6剖面与其东北侧的穿过芦山地震区汶川地震后完成的LMS4剖面的地壳电性结构既有相似性,但也存在明显的差别,其电性结构更复杂。研究表明,尽管2008年发生了汶川地震,但是龙门山断裂带受到的西北侧松潘-甘孜地块向SE的运动和对龙门山断裂带的推挤作用,以及东南侧四川盆地的阻挡作用仍然存在,同时龙门山断裂带西南端及其附近地区的地壳结构更复杂,而且还受到其西南侧川滇地块和鲜水河断裂等变形作用的影响,因此推测芦山地震与汶川地震既是相互独立的2次地震,但也有一定关联。  相似文献   

内蒙古达斯呼都格矿区综合地球物理场特征与找矿预测     

祁民 《地质与勘探》2017,53(6):1148-1154

内蒙古达斯呼都格矿区位于得尔布干成矿带西南段,区内成矿条件优越,成矿类型以斑岩型矿床为主,但工作区内地表草原覆盖严重,几乎没有基岩露头,传统地质手段难以奏效。本文通过地面高精度磁测、大功率激电扫面、音频大地电磁测深等综合物探方法,结合遥感、钻孔等资料,推测了该地区火山机构位置与岩体分布特征以及浅部铅锌矿的分布规律。音频大地电磁测深资料表明,本区岩体可分为两期,其中晚期岩体与成矿关系密切,为下一步矿产勘查指明了方向。  相似文献   

可控源音频大地电磁法在平阴县地质灾害调查中的应用效果   总被引：1，自引：0，他引：1  

宋希利  彭玉明  王仕昌 《山东国土资源》2010,26(7):13-16

可控源音频大地电磁新方法在济南市平阴县安城乡东凤凰村地裂缝调查中发挥了重要作用,物探成果异常明显,推测了与地裂缝形成有关的隐伏断层产状,分析了地裂缝成因,据野外实地调查和访问,物探推测成果符合事实。该法在地质灾害调查等工程物探领域值得推广应用。  相似文献   

长周期大地电磁测深研究——青藏高原东部LMT响应函数及应用   总被引：4，自引：2，他引：2       下载免费PDF全文

肖鹏飞  白登海  刘美  孔祥儒 《地震地质》2010,32(1):38

长周期大地电磁(LMT)是基于常规MT理论发展起来的电磁测深技术,青藏高原东部岩石圈较厚、视电阻率较低,应用LMT方法能够弥补常规MT仪器对低频信号响应的不足,获得有用的深部信息。文中概述了LMT的数据采集、处理及反演解释,并介绍了将LMT应用于东喜马拉雅构造结及其周围地区完成的长周期观测剖面——下察隅—玉树LMT剖面的岩石圈结构探测实例。实际观测表明,在重叠频段内LMT结果与常规MT具有良好的一致性;LMT数据处理实现的阻抗和倾子估计,在深部信息上具有更高的分辨率。LMT剖面结果揭示了青藏高原东部普遍存在地下低阻体,为局部地区部分熔融和地下流体存在的可能性提供了依据。LMT测深较好地弥补了常规MT方法在巨厚岩石圈和遇到低阻体时探测深度的局限性。  相似文献   

大地电磁法正演中多重网格法求解的广义傅里叶谱分析   总被引：1，自引：0，他引：1  

柳建新  郭荣文  童孝忠  刘颖  刘鹏茂 《吉林大学学报(地球科学版)》2011,41(5):1587-1595

为了准确预测和分析多重网格法用于大地电磁法正演计算的收敛效果,对多重网格法的收敛性进行了广义傅里叶谱分析。通常情况下,系数矩阵的傅里叶谱是复数,为了直观地判断、提取收敛信息,将谱转换到实数域。在实数域内,特征向量谱定量解释了二重网格法收敛慢的原因（最粗网格用Gauss-Seidel法求解）。传统的局部傅里叶谱分析没有考虑边界条件和模型参数的变化,在分析二重网格法求解收敛性时得出的渐进收敛估计与数值解偏差大。针对这一问题提出广义傅里叶谱分析,其结果与数值解接近（比如2-V（0,1）的广义傅里叶谱分析为0.706,真实值为0.710）。对五重网格法求解的高重广义傅里叶谱分析结果表明,随广义傅里叶谱分析分析重数的增加, 所求渐近收敛估计趋于收敛的数值结果。基于此得出高重广义傅里叶谱分析的经验公式。求得低重广义傅里叶谱分析,通过矫正近似得到高重广义傅里叶谱分析,其结果在本文2个例子有效。  相似文献   

The hydrothermal vent system of Mount Ruapehu,New Zealand — a high frequency MT survey of the summit plateau     

K.A. Jones  M.R. Ingham  H.M. Bibby 《Journal of Volcanology and Geothermal Research》2008

High frequency magnetotelluric (MT) measurements made on the summit plateau of Mount Ruapehu, some 1 km to the north of the presently active vent beneath Crater Lake, have been used to derive the electrical resistivity structure associated with the volcanic hydrothermal vent system. The entire summit plateau area is underlain at shallow depth by low resistivity which is inferred to be the result of hydrothermal alteration caused by rising volcanic gases mixing with local groundwater. Two areas of localised higher resistivity, one between 200 and 500 m depth beneath the central part of the plateau, and one at a depth of 1000 m below the northern part of the plateau, are interpreted as being the result of hydrothermal alteration at higher temperature forming chlorite dominated alteration products. These regions are believed to represent the locations of further heat pipes within the volcanic system. Both correlate with the locations of eruption centres on Ruapehu active within the last 10 ka.  相似文献   

Audio frequency magneto-telluric survey of Norikura Volcano in central Japan     

Kiyoshi Fuji-ta  Yasuo Ogawa  Masahiro Ichiki  Satoru Yamaguchi  Yutaka Makino 《Journal of Volcanology and Geothermal Research》1999,90(3-4)

Norikura Volcano has not been active during the last 10,000 years in spite of the activity of the surrounding volcanic mountains. To study past volcanic activities, geological studies were carried out extensively. However, quite a few geophysical investigations were conducted to contribute to volcanology. Our objective is to detect the present subsurface structure of Norikura Volcano and to define volcanic stratifications. In the vicinity of Norikura Volcano, geothermal fields are still active. Subsurface volcanic rocks in this area have been exposed to geothermal activity and altered. To comprehend volcanic stratifications of Norikura and geothermal activity, we conducted audio frequency magneto-telluric (AMT) surveys around Norikura Volcano. AMT survey is useful in clearly defining the resistivity structure related to volcanic regions. The AMT data were acquired over a frequency range 10 Hz–10 kHz. Decomposition analysis was applied to the tensor impedance data. Subsequently, apparent resistivity and phase data were inverted using a two-dimensional magneto-telluric (MT) inversion and a model of Norikura was derived. The final model manifests that the surface resistors are in agreement with andesite lava or dacite lava. As for the deeper structure, a horizontal conductor is situated above resistive basements. The alteration of the conductor was weak, while basement rocks were strongly altered and/or heated through the thermal activity. The existence of these layers seems to indicate the degree of thermal activity of Norikura Volcano.  相似文献