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1.
南汀河断裂带为滇西南地区活动断裂体系中规模最大的一条北东向断裂,其构造活动及地震危险性一直备受关注.本文基于覆盖云南境内南汀河断裂带的大地电磁测深宽频带阵列数据,利用大地电磁三维反演解释技术,首次获得了南汀河断裂带的精细三维深部电性结构.在上地壳深度,南汀河断裂带西南段与中段的电性结构表现出沿构造走向的高导条带特征,北东段表现为高阻结构.该高阻结构可能为临沧—勐海花岗岩体的电性反映,指示南汀河断裂可能未切穿该花岗岩带.在中下地壳深度,南汀河断裂带西南段存在大范围高导层,北东段则表现为整体性的高阻地壳,因此南汀河断裂北东段可能具有发生强震的介质结构背景.南汀河断裂带西南段的耿马地震区深部呈现北东向与北北西向的"X"型高导构造样式,该高导结构以南存在一个显著高阻异常体,1988年耿马MS7.2地震以及2015年沧源MS5.5级地震均发生于该高阻体与"X"型高导条带的电性边界.青藏高原东南缘绕东构造结流入滇西地区的中下地壳流可能受到南汀河断裂北东段中下地壳高阻体的阻挡而呈分流式分布于保山地块以及澜沧江断裂以东. 相似文献
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本文对一条布设在滇西盈江—龙陵地区的大地电磁剖面(苏典—中山剖面)数据进行了精细处理和二维反演解释,得到了测区较高置信度的二维电性结构.该电性模型纵向上表现为高阻-低阻-高阻的"三明治"式岩石圈电性结构,上地壳为平均厚度约为10km的高阻地层,在约6～16km地壳深度范围发育有电阻率为几欧姆米的显著高导层,下地壳底部和上地幔顶部表现为电性较为均匀的相对高阻层.横向上自西向东划分出以大盈江断裂带、龙陵—瑞丽断裂带为限的3个主要构造区域.壳内分布的高导层沿剖面表现出一定的横向不均匀性,其在龙陵—瑞丽断裂带下方消失,在该处形成了腾冲地块和保山地块的电性构造边界.电性结构表明,大盈江断裂附近高导层顶界面浅,两侧高阻体厚度小,因此难以形成较大规模的相互作用,致其附近浅震源、小震级的地震活跃;龙陵—瑞丽断裂两侧的高阻体较厚,易积累较大的应力,具有大震的深部孕震环境,故其附近发生过多次7级以上强震. 相似文献
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宁-芜矿集区及其西缘深部结构初探 总被引：4，自引：2，他引：2
为了探查宁(南京)-芜(湖)矿集区及其西缘地区上地壳结构及其与区域成矿作用的关系,在宁芜矿集区及其西缘布设两条大地电磁测深剖面(江宁区-姑山,巢湖-当涂),通过数据处理、分析和反演,获得了宁芜矿集区10 km以内地壳电性结构模型.大地电磁测深及重力多尺度边缘检测结果表明:(1)宁芜矿集区自南向北表现为低-高-低的电性结构特征,南段深部存在低阻体,向上延伸至浅部,中段深部发育巨型高阻体上隆至浅部,倾向南西,推测可能是巨型花岗岩体,北段低阻体发育深度大,向上延伸至浅部时分叉并上升至地表;(2)揭示了滁河断裂和长江断裂带的存在; 3线剖面东段与2线南段的低阻体位置较为一致,推测为岩浆喷发通道,在含山附近发现两条电性梯度带,3线剖面的电性结构特征可能反映了区域经历了先挤压、后拉伸的演变过程. 相似文献
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在广西龙滩库区布置2条北北西-南东东向大地电磁探测剖面进行了32个测点的观测,观测频段为320 Hz~1000 s.对2条剖面上测量和计算得到的各种电磁参数、深部电性结构图像以及库区地质构造、岩性和水域分布等进行分析研究.结果显示库区发育的6条断裂在电性上表现为不同程度的电性差异边界,其中拉浪-达良断裂和拉色-辉马断裂为库区主要断裂带.库区深部电性结构总体表现为纵向上自地表到20 km深度呈现高-低-高的波浪起伏的三层结构,横向上呈明显的高低电阻块状组合样式.龙滩库区4个地震丛集区的震源都位于高、低电阻接触带附近,其中3个地震丛集区的震源位于低阻特性的石炭系地层的下部,为岩溶水体诱发地震;发生最大震级的地震丛集区的震源位于上宽下窄似"铆钉状"的高阻体下部,推测是因水库蓄水后水体压力增大和库水渗透作用下在聚集高变形能的脆性高电阻体内部发生的地震. 相似文献
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经过数十年的努力,中国学者针对青藏高原东缘地壳上地幔探测,累积完成超过20000 km的大地电磁测深剖面,取得了一系列重要科学数据和认识,为青藏高原东缘构造格局、地壳上地幔电性结构、地震机制和动力学研究奠定了基础.根据青藏高原东缘的主要构造和断裂分布特征,本文重点对龙门山构造带、川滇构造带和三江构造带三个构造带分区进行研究,主要依据大地电磁探测工作成果和壳幔电性结构特征,系统地对青藏高原东缘地壳上地幔电性结构、与扬子西缘接触关系、汶川地震和芦山地震的电性孕震环境及弱物质流通道等几个方面进行了梳理和分析.一是青藏高原东缘地壳表层岩块和物质沿壳内高导层向龙门山造山带仰冲推覆,表现为逆冲推覆特征的薄皮构造;二是高原东部地壳中下部及上地幔顶部向龙门山造山带和上扬子地块西缘岩石圈深部俯冲,呈现刚性的上扬子地块西缘高阻楔形体向西插入柔性青藏块体的楔形构造;三是将汶川地震和芦山地震的震源投影到大地电磁剖面上,发现震源位于剖面下方的高阻块体与低阻体之间靠近高阻体的一侧,龙门山构造带岩石圈表现出高阻、高密度和高速的"三高"特征,这种非均匀电性结构可能构成地震孕育发生条件;四是川滇和三江地区的多条大地电磁剖面探测结果表明,在青藏高原东缘中下地壳存在下地壳流和局部管道流,大地电磁结果对其空间分布形态、位置及大小进行了较好的刻画.根据研究区壳幔电性结构特征的构造解析和综合实例分析,总结了青藏高原东缘六类壳幔电性结构模型,提出了下一步重点研究领域和目标.总之,青藏高原东缘壳幔电性结构的研究对揭示研究区岩石圈结构和构造格局提供了重要依据,对油气及矿产资源远景评价提供了背景资料,对"Y"型多地震区的构造关系和发震机理研究具有重要指导意义. 相似文献
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为研究华北坳陷中南部河南地区的深部电性结构和该区3次破坏性地震的深部孕震背景，采用宽频带大地电磁测深法对该区深部的电性结构进行探测。使用NLCG二维反演方法对TE、TM模式进行联合反演，最终获得研究区的深部电性结构。结果显示，以新乡-商丘断裂为界，其北部的北华北坳陷中的内黄隆起、东濮凹陷的电性结构相对简单，为低阻、高阻2层结构，与该区地壳由沉积盖层和基底整体性较好的坚硬地块结晶基底组成相对应。新乡-商丘断裂以南的南华北坳陷中的构造单元深部的电性结构相对复杂，纵向上表现为低—高—低3层结构，横向上高阻、低阻交互出现，分析其可能与受到扬子板块与华北板块南缘相互俯冲碰撞影响有关。而北华北坳陷因边界断裂———新乡-商丘断裂的调控，受到扬子板块和秦岭-大别造山带造山作用的影响较小。1342年和1918年河南通许2次破坏性地震的震源位于太康隆起下方的高、低阻边界交接区域，1737年河南封丘■级地震的震源位于壳内高、低阻梯度带附近。 相似文献
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滇东北地区位处不同构造分区的交界地带,发育有多样的断裂构造,其中昭通—鲁甸断裂和小江断裂带的部分区段均具备积累高应力的条件,具有较强的孕震潜力.本文基于覆盖巧家、东川、鲁甸等地区采集的区域大地电磁阵列观测数据,通过大地电磁三维反演,获得了该地区的三维电性结构的水平和垂直切片,完整地揭示了滇东北地区的深部电性结构特征.反演结果表明,昭通—鲁甸断裂在10 km深度以内发育有多个局部高阻区,小江断裂带的巧家—东川段的东侧、东西两支交汇处在上地壳均表现为高阻,这些区域均展示出更强的孕震能力.根据低阻异常的分布,推测昭通—鲁甸断裂和小江断裂下方的低阻构造在中下地壳的多个位置发生连通.本文将研究区的地表热流、岩石圈有效弹性厚度、地震与电性结构结合分析,推测在滇东北深部低阻层可能存在下地壳流,并且下地壳流的塑性流动为鲁甸的地震活动提供了深部动力来源. 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
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广西钦防结合带是厘定钦杭构造结合带西南段构造位置的关键所在,该带发生了华南内陆有历史记载以来最大的地震——1936年广西灵山M6(3/4)地震,因此该区域也是研究华南板内地震成因的理想场所.本文展示了一条自北西向南东、跨过广西钦防结合带和灵山地震区的宽频带大地电磁探测剖面,利用三维反演技术获取沿剖面的电阻率结构模型,结合地质、重力、波速比、GPS和大地热流等成果,对钦防结合带主要断裂的深部延展形态和构造属性进行了综合解译,结果揭示:(1)峒中-小董断裂、防城-灵山断裂东支、合浦-北流断裂东支均为超壳深大断裂,深部发育壳幔韧性剪切带,其中峒中-小董断裂和合浦-北流断裂东支分别为倾向北西和南东的电性分界带,防城-灵山断裂在上地壳呈现“花状”构造样式,深部为向东南缓倾斜的电性分界带.(2)峒中-小董断裂西北侧的湘桂被动陆缘具有成层性的电阻率结构和相对稳定的布格重力异常值,符合扬子地块东南缘局部破坏的准克拉通构造属性,其东南侧的钦防结合带和云开岩浆弧呈现电性结构高低阻混杂、高起伏布格重力异常的特征,揭示该区属于历经多期次构造演化改造的物质组合属性;钦防残留洋盆下方的巨型高阻体可能是华南洋消亡、... 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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Peaks in the Cascade Range in northern Washington State are on average ～800 m higher than in southern Washington. The influences of differential valley excavation and variations in hillslope length and average slope on these altitudinal trends were tested using a 3‐dimensional model for isostatic rock uplift and calculations of hillslope length and slope respectively. The magnitude of isostatic peak uplift calculated by the model is highly dependent on the flexural rigidity (D) and the related effective elastic thickness (Te) of the crust of this region. Crustal rigidity was constrained using published estimates and by estimating the depth of the seismogenic zone in the area (D > 1 × 1023 Nm and Te > 24 km). With these constraints, isostatic compensation due to differential erosion added < 700 m and 300 m, or < 25% overall, of height to peaks in the northern and southern Cascades, respectively. Deeper valley incision in the northern Cascades accounts for < 300 m of the 800 m difference in peak altitudes between north and south. Similarly, variation in valley spacing and slope account for < 350 m of the difference in mean altitude between northern and southern regions. Hence, at least several hundred m difference in altitude between the northern and southern regions of the Cascades in Washington must be due to tectonic, geologic, or geophysical factors rather than surficial and geomorphic effects like isostatic response to valley incision and hillslope geometry. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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A list of volcanic eruption plumes observed to ascend into or near the stratosphere since 1883 shows that the volcanoes divide readily into two groups, one at low and one at higher latitudes. A model for the rise of a buoyant volcanic plume rise as applied to volcanic eruptions is corrected for realistic temperature profiles and for the finite vertical extent of the resultant debris clouds. The utility of the model can be questioned, however, owing to the highly uncertain and variable nature of the efficiency of use of heat energy of buoyant rise. The observed correlation of stratospheric plumes with climatic effects indicates that those plumes nearer the equator have the largest impact on surface temperatures. Analysis of the observations also suggests that injection of debris into the stratosphere is more important in determining the effect on climate than either the total volcanic explosivity of the eruption or the actual height reached within the stratosphere. 相似文献
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Barry Saltzman 《Pure and Applied Geophysics》1964,57(1):153-160
Summary A possible formal approach to a closed steady-state theory of the mean axially-symmetric variables is outlined. The approach involves alternating iterative solutions of the energy and momentum equations. In these equations the effects of transient eddy phenomena of all frequencies are assumed to be parameterized in terms of the mean symmetric variables. 相似文献
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The earth's largest positive geoid height anomalies are associated with subduction zones and hotspots. Although the correlation with subduction has been noted for many years, the correlation with hotspots is fully evident only when the subduction-related geoid highs are removed from the observed field. Using the assumption that subducted lithospheric slabs are uncompensated and are thermally re-equilibrated with the asthenosphere at the maximum depth of earthquakes, the expected geoid anomaly over subduction zones is calculated. This field provides a satis-factory fit to the observed circum-Pacific high. Subtraction of this predicted anomaly leaves a residual field which is correlated, at greater than the 99% confidence level, with the distribution of hotspots. Broad residual geoid highs occur over the central Pacific and the Africa/eastern Atlantic regions, the same areas where the hotspots are concentrated. The mass anomalies associated with hotspots and subducted slabs apparently control the location of the earth's spin axis. 相似文献
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Concentrations of Cd, Cr, Cu, Ni and Pb were determined in filtered water, suspended particulate matter, and bottom sediments from a 2000 km section of the Ob and Irtysh Rivers. Dissolved Cd, Cr, Cu and Ni concentrations are similar to, or higher than, results from other Russian Arctic and large world river-estuaries. Concentrations of Cd, Cr, Cu, Ni and Pb in suspended particulate matter are generally comparable to results from other Russian Arctic and large world rivers and estuaries. Comparison of trace metal ratios in crustal material and suspended particulate matter and bottom sediment suggests that the source of Cr, Cu and Ni is continental weathering. Particulate Cd and Pb are elevated relative to their crustal abundance, suggesting a source of these metals to the Ob-Irtysh in addition to continental weathering. 相似文献
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Pore water testing and analysis: the good,the bad,and the ugly 总被引：8，自引：0，他引：8
The increasingly common practice of collecting and assessing sediment pore water as a primary measure of sediment quality is reviewed. Good features of this practice include: pore water is a key exposure route for some organisms associated with sediments; pore water testing eliminates particle size effects; pore water analyses and tests can provide useful information regarding contamination and pollution. Bad features include: pore water is not the only exposure route; pore water tests lack chemical or biological realism: their "sensitivity" relative to other tests may be meaningless due to manipulation and laboratory artifacts; many sediment and surface dwelling organisms are not directly influenced by pore water. Bad features can become ugly if: other exposure pathways are not considered (for toxicity or bioaccumulation); manipulation techniques are not appropriate; pore water tests are inappropriately linked to population-level effects. Pore water testing and analyses can be effective tools provided their limitations are well understood by researchers and managers. 相似文献
20.
Introduction The June 4, 2000 southern Sumatra, Indonesia, earthquake (16h28min26.2s UTC, 4.72, 102.09, 33 km, MS=8.0 [IRIS]) occurred under the Indian Ocean, near the Mentawai fault, along the well-known Sumatran subduction zone and the great Sumatran fault, all of which trend northwest-southeast. 1 800 houses were totally destroyed, 10 196 were heavily damaged, and 18 378 were slightly damaged by the earthquake. At least 97 people were killed, 1 900 were injured, and 122 000 were left… 相似文献