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对青藏高原东北缘海原弧形构造区（105deg;～107deg;E，36deg;～37.5deg;N）的5条大地电磁测深剖面进行处理分析和二维反演，得到研究区内东西宽约160 km、深约60 km范围的地壳电性细结构. 结果表明: 研究区呈现南西——北东的带状分布特征. 由南西——北东可分为6个电性区块，依次为西吉盆地(Ⅰ)、西、 南华山隆起(Ⅱ)、兴仁堡-海原盆地(Ⅲ)、中卫-清水河盆地(Ⅳ)、中宁-红寺堡盆地(Ⅴ)和鄂尔多斯西缘带(Ⅵ). 各区块在平面上呈北西撒开、 南东收缩的ldquo;扫帚状rdquo;形态；弧形构造区弧顶附近构造完整、规模大，自弧顶向北西、南东两端构造规模逐渐减小. 地表到深度10 km左右，西、南华山隆起和鄂尔多斯西缘带呈高阻特性，西吉、兴仁堡-海原、中卫——清水河和中宁-红寺堡4个盆地的电阻率较低且呈盆地凹陷形状. 其中兴仁堡-海原盆地电性基底最深，显示为南西深北东浅的ldquo;簸箕状rdquo;起伏形态. 研究区发育不连续的壳内低阻带，与该区中、强震活动密切相关. 1920年海原大震区存在明显的电性结构差异，震区南西侧和上部区域为相对高阻，北东侧和下部区域为相对低阻. 相似文献
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海原一六盘山构造带是青藏高原东北缘地区的一条重要边界,在海原断裂带和六盘山断裂带接触区形成了特殊的马东山挤压阶区,本文对跨过该挤压阶区一条密集测点大地电磁剖面数据进行了处理和二维反演,获得的深部电性结构图像揭示在马东山挤压阶区深部电性结构表现为在高阻背景下镶嵌多个向西南倾斜的低阻条带电阻率结构样式,并在深度约25 km汇聚到中下地壳低阻层内,共同组成"正花状"结构;海原一六盘山构造带西南侧到陇中盆地区间呈现高、低阻相互"楔合"的深部结构特征,而其东北侧的鄂尔多斯西缘带自地表到中下地壳为较完整的高阻块体.另外结合跨过海原断裂带中段和西秦岭造山带的大地电磁探测结果,对海原一六盘山构造带分段性及其两侧的陇中盆地和鄂尔多斯地块的接触关系进行了研究分析.大地电磁探测成果佐证了在海原断裂带中段为具有走滑特点的断裂,而其尾端与六盘山断裂带斜交区域的马东山地区发生了强烈的逆冲推覆与褶皱变形;活动构造研究发现沿海原断裂带所产生的左旋走滑位移被其尾端的马东山、六盘山以东西向的地壳缩短调节吸收,GPS观测表明青藏高原东北缘地区现今构造变形分布在海原一六盘山构造带以西上百公里的范围内,陇中盆地一海原一六盘山构造带和鄂尔多斯地块一线的深部电性结构图像也很好地解释了该区变形状态:海原一六盘山构造带带及西南盘的陇中盆地的中下地壳非常破碎,在青藏高原向北东方向的推挤下容易发生变形,而北东盘鄂尔多斯地块地壳结构完整,很难发生构造变形.对海原一六盘山构造带马东山阶区和龙门山构造带的深部电性结构及变形特征等进行了比较分析,发现该区有与2008年汶川地震相似的深部构造背景,应重视该区强震孕育环境的探测研究. 相似文献
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沿穿过古浪大震震中区乐都—武威—白马岗北北东方向约340 km长的剖面,进行了16个测点的大地电磁探测.使用Robust技术处理观测数据,分析了视电阻率、阻抗相位、Swift二维偏离、最佳电性主轴方位角等参数,并采用NLCG二维反演技术对TE和TM两种模式的数据进行了二维反演模拟.结果表明：大通山—大坂山、西海原、皇城—双塔、龙首山和北大山5条断裂为明显的电性边界,其中西海原、皇城—双塔、龙首山和北大山断裂由西南向东北依次变浅变缓并在深部收敛于壳内低阻层上.沿剖面上地壳的电性构造较中下地壳的复杂,上地壳自西南向东北可分为中祁连隆起、北祁连褶皱带、冷龙岭隆起、武威盆地、潮水盆地和北大山隆起6个构造单元样式,显示与地表地质调查一致的构造格局;而在中、下地壳,武威盆地、潮水盆地和北大山隆起为一体,都属于阿拉善地块.中祁连和阿拉善地块电性成层性好,存在西南深、东北浅的壳内低阻层,北祁连褶皱带和冷龙岭隆起带电性结构复杂,高、低电阻体相间.1927年古浪地震震中区西南侧和上方区域的电阻率为高电阻率区,下方和东北侧区域为低电阻率区,处于电性结构明显呈台阶状陡变的地带,表明古浪地震是一次与断坡作用有关的地震. 相似文献
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在横跨鄂尔多斯盆地西缘构造带北段的查甘池—银川—五湖洞约200 km长的东西向剖面上,进行了67个测点的大地电磁探测.使用“远参考道”和Robust技术处理数据.分析了各测点视电阻率、阻抗相位、二维偏离度、电性主轴方位角、磁实感应矢量等参数,采用NLCG二维反演方法对TE和TM两种模式的数据进行了二维反演.得到的二维电性结构表明,沿剖面查汗断裂带、贺兰山东缘断裂带和黄河断裂带是明显较大型电性边界,为超壳断裂带,而三关口断裂带深部延深不大.沿剖面阿拉善地块、贺兰山褶皱带、银川断陷盆地和鄂尔多斯地块具有明显不同的深部电性结构特征.阿拉善地块内部除浅表电阻率较低外,以下到深度约50 km都表现为高电阻特性.贺兰山褶皱带电性结构复杂,电阻率高低相间.银川盆地具有上宽下窄最深达约8 km低阻层,具有断陷盆地特征.鄂尔多斯地块具有低-高-低的深部电性结构特征,成层性较明显. 相似文献
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在青藏高原东北缘至鄂尔多斯地块沿玛沁—兰州—靖边剖面进行62个测点的大地电磁观测,采用Robust技术对观测数据进行了处理和张量阻抗分解.分析了视电阻率和阻抗相位曲线、二维偏离度、区域走向.采用RRI二维反演技术进行了资料的反演解释,二维剖面的电性结构显示：（1）玛沁断裂带、兰州深断裂带、马家滩—大水坑断裂带将剖面分为4个电性区块：巴颜喀拉地块、秦祁地块、边界带和鄂尔多斯地块.（2）区块1、2和4的地壳电性结构有类似特点：上地壳为高阻层,下地壳上部为低阻带,下地壳下部到上地幔电阻率随深度逐渐升高.区块3电性成层性差、结构复杂,是现今构造活动较强烈的地区.（3）玛沁断裂带、海原断裂带和罗山—云雾山断裂带为较陡立的超壳断裂带;西秦岭北缘断裂带为壳内断裂带. 相似文献
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本文对跨过西秦岭造山带(中段)的阿坝—若尔盖—临潭—兰州大地电磁剖面(WQL-L1)所采集到的数据进行了精细化处理分析和二维反演研究,结合跨过2013年岷县漳县地震区的WQL-L6剖面大地电磁探测结果和以往的地质与地球物理资料,对西秦岭造山带(中段)的深部电性结构、主要断裂带延伸状况以及与南北两侧地块的接触关系等进行了分析研究,结果表明:东昆仑断裂带塔藏段、迭部—白龙江断裂和光盖山—迭山断裂带共同组成了东昆仑断裂系统,分隔了松潘—甘孜地块和西秦岭造山带(中段);西秦岭北缘断裂带为主要的高角度南倾大型电性边界带,延伸深度穿过莫霍面;临潭—宕昌断裂带具有电性边界带特征,其延伸情况具有东、西差异.西秦岭造山带(中段)自地表到深度约20km范围表现为东北和西南浅、中部深的倒"梯形"高阻层,在高阻层之下广泛发育低阻层,低阻层与高阻层相互契合,呈现相互挤压堆积的式样,其西南侧的松潘—甘孜地块中下地壳存在西南深、东北浅低阻层,其东北侧的陇西盆地具有稳定的成层性结构,显示出西秦岭造山带(中段)正处于松潘—甘孜地块向北挤压和陇西盆地向南的阻挡挤压作用中.松潘—甘孜地块从西南向东北推挤、东北侧陇西盆地相对阻挡的相互作用是2013年岷县漳县6.6级地震发生的外部动力学机制,同时地震震源区特殊介质属性是该次地震发生的内部因素.西秦岭造山带(中段)中上地壳倒"梯形"高阻体埋深西薄、东厚的分段差异与该段内部中强地震分布差异有关.东昆仑断裂玛沁段和塔藏段内部的深部电性结构差异和延伸状况与东昆仑断裂自西向东走滑速率减小有内在联系. 相似文献
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给出了定边－景泰大地电磁剖面探测结果并对其进行了分析．鄂尔多斯块体内部电性结构简单,电性界面成层性好,而在其西缘弧形断裂带,电性结构复杂,电导率横向变化较大．在弧形断裂带上地幔低阻层埋藏深度加大,这与北面的银川断陷盆地上地幔结构上隆形成反照,经分析认为银川断陷盆地属于拉张性质,而弧形断裂带属于挤压性质,由于均衡调整作用,造成了两者上地幔结构的反差．深部电性结构在大罗山－惠安堡之间有一局部上隆,经分析认为此处可能为深大断裂,南北构造带仅在此通过． 相似文献
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Through the analysis and 2-D inversion for the 5 profiles in Haiyuan arcuate tectonic region (105°～107°E,36°～37.5°N) in the northeastern margin of Qinghai-Xizang Plateau, we have obtained the electric structure within a range of 160 km in width (east-west) and 60 km in depth in the studied area. The results show that the crustal electric structure can be divided into 6 sections, corresponding respectively to Xiji basin (Ⅰ), Xihuashan-Nanhuashan uplift (Ⅱ), Xingrenbu-Haiyuan basin (Ⅲ), Zhongwei-Qingshuihe basin (Ⅳ), Zhongning-Hongsibu basin (Ⅴ) and west-margin zone of Ordos (Ⅵ) from the southwest to the northeast. The crustal electric structure is characterized by a broom-shaped pattern, which scatters to the northwest and shrinks to the southeast. The structures in the top part of Haiyuan arcuate tectonic region are complete and large, however, they diminish from the arc top to the northwest and southeast ends. In the depth from 0 km to 10 km, the resistivity is high in the sections Ⅱ and Ⅵ, but relatively low in the other four sections, showing a similar pattern of basin depression. The electrical basement in the section Ⅲ is the deepest, displaying a "dustpan" shape that is deep in the southwest and shallow in the northeast. A series of discontinuous zones with high conductivity exist in the middle-lower crust in Haiyuan arcuate tectonic region, which is possibly related to the moderate and strong earthquakes in the region. The resistivity distribution in the focal area of the 1920 Haiyuan earthquake is significantly heterogeneous with an obviously high conductivity zone near the hypocenter regime. 相似文献
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祁连山东端冷龙岭隆起及其附近地区是青藏高原东北缘与阿拉善地块强烈相互挤压碰撞区域,也是历史地震活动极为强烈区域.为了揭示冷龙岭隆起及其附近区域的断裂深部延伸状况、强震孕育构造背景以及区域动力学特征等,我们在已有大地电磁数据的基础上,新近在冷龙岭隆起附近以及西南侧区域进行了数据采集,获得了一条自西南向北东穿过西秦岭地块、陇西盆地、祁连山冷龙岭隆起和阿拉善地块的长约460 km的大地电磁剖面(LJS-N)数据,并利用三维电磁反演成像技术对全剖面数据进行了反演,同时也对位于该剖面西侧约80 km外的一条大地电磁剖面(DKLB-M)数据进行了三维反演成像.2条电磁探测剖面结果均揭示了祁连—西海原断裂带展现为略向西南倾斜的大型超壳电性边界带,该断裂是祁连山东端冷龙岭隆起区域最重要的主边界断裂,其北东侧和西南侧地块的深部电性结构呈现出截然不同电阻率分布特征,其西南侧的南祁连地块、陇西盆地以及西秦岭地块在地壳尺度展示为埋深深浅不一的高-低-次高阻结构特点,而其北东侧古浪推覆体表现为西南深、东北浅“鼻烟壶”状较完整的高阻结构特征,再往北到阿拉善地块则呈现为高-低-次高水平三层结构样式.1927年M 8.0古浪、1954年M 7.0民勤和2016年M 6.4门源地震的震源都处于统一的高阻古浪推覆体之中.在青藏高原北东向挤压作用的控制下,祁连山东端冷龙岭隆起区域的祁连—西海原断裂、祁连山北缘断裂和红崖山—四道山断裂以叠瓦状向北北东向顺序推覆拓展到阿拉善地块,这种拓展作用是该区中强地震的动力来源. 相似文献
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ELECTRICAL STRUCTURE OF UPPER CRUST IN THE SOURCE REGION OF JINGGU YUNNAN MS6.6 EARTHQUAKE AND THE SEISMOGENIC ENVIRONMENT 
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下载免费PDF全文 The October 7, 2014 MS6.6 earthquake in southwest of Jinggu in the southwestern Yunnan Province occurred as the result of shallow strike-slip faulting within the crust of the Eurasia plate in the broad plate boundary region between the India and Eurasia plates. The strike of fault plane is 140°, and the aftershock distribution shows that the rupture plane is also NNW-trending. Tectonics of the region are controlled by the convergence of the India plate with Eurasia, which has driven the uplift of the Himalayas to the west of this earthquake, and has caused the formation of numerous intraplate continental transform structures in the surrounding region. The pattern of elastic-wave radiation from the earthquake is consistent with the shock occurring either as the result of right-lateral faulting on a northwest-trending fault or as the result of left-lateral faulting on a northeast trending fault. Faults of both types have been mapped in southwestern Yunnan, and it is unclear at this time which type of fault hosted this event. Magnetotelluric survey line is across Jinggu earthquake zone. The advanced data processing and analysis technology of MT is employed and the quantitative data from field surveys are analyzed to acquire the reliable electrical model. The MT data are inverted using nonlinear conjugate gradient (NLCG) inversion algorithm. At last, the interpretation of the electrical model is performed considering the geology and the other geophysical data. Based on the final inversion model of the target profile, it is found that:(1) Electrical structure of the source region can be divided into four layers:The surface is relatively low resistivity layer(0~5km), consisting mainly of Mesozoic and Cenozoic Basin sedimentary rocks, the value of resistivity is 100Ω·m; The high resistivity layer(5~10km) in upper crust mainly consists of Proterozoic metamorphic rocks, with resistivity higher than 1 000Ω·m; there are the upper crust high-conductivity layer(15~25km) and crust-mantle transition zone(blow 25km); (2) The focal depth of the Jinggu earthquake is about 10km, which locates in the interface between high resistivity layer and high-conductivity layer; (3) Most of the focal depths of the aftershocks are in the range of 5km and 10km, and the two depths(5km & 10km) are corresponding to the resistivity gradient belt. 相似文献
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玛沁-兰州-靖边地震测深剖面地壳速度结构的初步研究 总被引：75，自引：27，他引：75
为研究青藏高原块体和鄂尔多斯地块间的相互作用和构造变形的深部驱动机制,布设了1000km长的玛沁-兰州-靖边综合地球物理探测剖面.本文只介绍由人工地震观测资料所得到的初步结果.地壳分层性明显,以C界面为界,总体上可分为上、下地壳两大部分,每个部分又包含一些次一级的界面;横向变化的总趋势是从东北至西南地壳逐渐变厚,地壳厚度的变化主要由下地壳厚度的变化所引起;地壳平均速度,总的变化趋势是自东北向西南逐渐降低,其中在泽库以西和海原地区的速度值明显偏低;在泽库以西存在多个壳内低速层,在海原附近存在一个低速层;壳内反射界面,沿测线由东北至西南逐步增多;从地震反射波形来看,在海原地区Pc波非常强,且延续时间长;另外,在海原地区和泽库以西地区Pm波的复杂性系数很大,远远大于其他地段的值.以上结果表明,泽库以西地区和海原地区地壳-上地幔存在着明显结构异常,反映了巴颜喀拉地块和柴达木地块、祁连地块和鄂尔多斯地块间的相互作用 相似文献
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佳木斯地块及东缘是中国东北地区的重要地质构造单元. 为探测该地区地壳深部结构与构造关系,沿桦南—饶河实施了240 km的大地电磁测深的探测研究. 采用光滑模型二维反演方法对桦南—饶河大地电磁剖面的探测数据进行了二维反演和综合地球物理解释. 研究结果揭示了研究区断面域的电性结构：(1)剖面西段具有稳定的高阻特征且具有稳定的岩石圈厚度（约90km）,在十几公里深度范围存在壳内高导层,该区段对应佳木斯地块. (2)剖面中部具有明显的电性梯度带,该梯度带反映了佳木斯地块的东界位置及其深部的结构形态. (3)剖面东段电性特征揭示了佳木斯地块以东区段浅部为逆冲推覆体,深部为多个高阻块体和低阻条带相间的电性结构,这些高阻块体可能为早期俯冲的岩石圈残片. 相似文献
17.
Data from ten magnetotelluric (MT) stations over the Wind River Uplift and adjacent basins are interpreted with constraints from the Consortium for Continental Reflection Profiling (COCORP) seismic reflection data and from gravity data. The MT data reveal the general configuration of the conductive basins and resistive uplifts; low resistivity zones are interpreted as faults which correspond to those visible in the COCORP sections.
The Wind River Thrust Fault is modelled as a conductive zone that can be traced to a depth of at least 20 km, and the crust beneath the Green River Basin is about 40 km thick.
The modelled constant dip of the Wind River Thrust is consistent with a tectonic model of lateral compressive stress. 相似文献
18.
ELECTRICAL STRUCTURE OF THE 2017 MS7.0 JIUZHAIGOU EARTHQUAKE REGION AND THE EASTERN TERMINUS OF THE EAST KUNLUN FAULT 下载免费PDF全文
下载免费PDF全文 SUN Xiang-yu ZHAN Yan ZHAO Ling-qiang CHEN Xiao-bin LI Chen-xia SUN Jian-bao HAN Jing CUI Teng-fa 《地震地质》1979,42(1):182-197
The East Kunlun Fault is a giant fault in northern Tibetan, extending eastward and a boundary between the Songpan-Ganzi block and the West Qinling orogenic zone. The East Kunlun Fault branches out into a horsetail structure which is formed by several branch faults. The 2017 Jiuzhaigou MS7.0 earthquake occurred in the horsetail structure of the East Kunlun Fault and caused huge casualties. As one of several major faults that regulate the expansion of the Tibetan plateau, the complexity of the deep extension geometry of the East Kunlun Fault has also attracted a large number of geophysical exploration studies in this area, but only a few are across the Jiuzhaigou earthquake region. Changes in pressure or slip caused by the fluid can cause changes in fault activity. The presence of fluid can cause the conductivity of the rock mass inside the fault zone to increase significantly. MT method is the most sensitive geophysical method to reflect the conductivity of the rock mass. Thus MT is often used to study the segmented structure of active fault zones. In recent years MT exploration has been carried out in several earthquake regions and the results suggest that the location of main shock and aftershocks are controlled by the resistivity structure. In order to study the deep extension characteristics of the East Kunlun Fault and the distribution of the medium properties within the fault zone, we carried out a MT exploration study across the Tazang section of the East Kunlun Fault in 2016. The profile in this study crosses the Jiuzhaigou earthquake region. Other two MT profiles that cross the Maqu section of East Kunlun Fault performed by previous researches are also collected. Phase tensor decomposition is used in this paper to analyze the dimensionality and the change in resistivity with depth. The structure of Songpan-Ganzi block is simple from deep to shallow. The structure of West Qinlin orogenic zone is complex in the east and simple in the west. The structure near the East Kunlun Fault is complex. We use 3D inversion to image the three MT profiles and obtained 3D electrical structure along three profiles. The root-mean-square misfit of inversions is 2.60 and 2.70. Our results reveal that in the tightened northwest part of the horsetail structure, the East Kunlun Fault, the Bailongjiang Fault, and the Guanggaishan-Dieshan Fault are electrical boundaries that dip to the southwest. The three faults combine in the mid-lower crust to form a "flower structure" that expands from south to north. In the southeastward spreading part of the horsetail structure, the north section of the Huya Fault is an electrical boundary that extends deep. The Tazang Fault has obvious smaller scale than the Huya Fault. The Minjiang Fault is an electrical boundary in the upper crust. The Huya Fault and the Tazang Fault form a one-side flower structure. The Bailongjiang and the Guanggaishan-Dieshan Fault form a "flower structure" that expands from south to north too. The two "flower structures" combine in the high conductivity layer of mid-lower crust. In Songpan-Ganzi block, there is a three-layer structure where the second layer is a high conductivity layer. In the West Qinling orogenic zone, there is a similar structure with the Songpan-Ganzi block, but the high conductivity layer in the West Qinling orogenic zone is shallower than the high conductivity layer in the Songpan-Ganzi block. The hypocenter of 2017 MS7.0 Jiuzhaigou earthquake is between the high and low resistivity bodies at the shallow northeastern boundary of the high conductivity layer. The low resistivity body is prone to move and deform. The high resistivity body blocked the movement of low resistivity body. Such a structure and the movement mode cause the uplift near the East Kunlun Fault. The electrical structure and rheological structure of Jiuzhaigou earthquake region suggest that the focal depth of the earthquake is less than 11km. The Huya Fault extends deeper than the Tazang Fault. The seismogenic fault of the 2017 Jiuzhaigou earthquake is the Huya Fault. The high conductivity layer is deep in the southwest and shallow in the northeast, which indicates that the northeast movement of Tibetan plateau is the cause of the 2017 Jiuzhaigou earthquake. 相似文献