共查询到20条相似文献，搜索用时 218 毫秒
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本研究使用中国数字地震台网（CDSN）（2009—2016）走时数据开展青藏高原地壳地震波速度三维层析成像研究,获得分辨率达到1°×1°×20 km的青藏高原地壳S波三维速度结构和泊松比分布.结果表明,分布在可可西里和羌塘北部的高钾质和钾质火山岩带,其上地壳到下地壳都存在S波波速扰动负异常和高泊松比.说明第三纪青藏高原隆升过程中,由于大陆碰撞使三叠纪的东昆仑缝合带重新破裂,造成大量壳幔混合熔融物质上涌和火山喷发,进而揭示了青藏高原北部新生代火山岩的存在与青藏高原的形成和隆升密切相关;青藏高原新生代裂谷位于中下地壳S波速度扰动负异常带的两侧,裂谷带之下的中下地壳泊松比减小到0.22以下.裂谷带之下中下地壳的S波速异常分布和泊松比值可以推断青藏高原新生代裂谷深达中地壳底部,这个推论与密度扰动三维成像的相关结论一致.青藏高原S波速度和泊松比在下地壳至壳幔边界随深度产生急剧变化,说明地壳内部发生了大规模的层间拆离和水平剪切;青藏高原东构造结之下泊松比高达0.29~0.33,S波速度扰动为负异常,推断东构造结下方地壳主要由坚硬的蛇纹石化橄榄岩组成;青藏高原中下地壳S波速负异常区范围大面积扩大,地壳底部几乎被S波速低值区全部覆盖.下地壳S波异常分布特点可能反映下地壳管道流的影响. 相似文献
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气体是识别构造带展布和活动的敏感组分。对唐山断裂带高空间分辨率气体地球化学测量数据进行了变异函数计算,分析了断裂带活动性与断裂带气体浓度的定量关系。结果表明,断裂带本身结构特性是控制断裂带气体空间分布的主要因素,高倾角断裂在地表以狭长条带状为主要特征,分布气体浓度高值异常,交会处气体浓度高值异常以环带形式围绕断裂分布。沿断裂带走向,各气体浓度呈高值分布,利用变异函数计算,确定各气体组分在测量区域内气体浓度与构造相关的空间范围,据此确定了唐山断裂各段构造敏感气体组分,在断裂带周边圈定出断裂带活动性重点监测区域。断裂带气体浓度克里金插值分析结果表明,唐山地区滦县—乐亭断裂带活动性较强,唐山断裂带次之,蓟运河断裂带活动性最弱。断裂带交会处,浓度高值异常分布更加明显。 相似文献
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Yu. O. Kuzmin 《Izvestiya Physics of the Solid Earth》2013,49(5):626-642
The results of analyzing the long (20–50 years) time series of geodetic observations carried out in the regions with enhanced seismotectonic activity (Kopet Dag, Kamchatka, and California) are presented. It is established that recent vertical and horizontal displacements in the fault zones estimated by instrumental geodetic observations with increased spatiotemporal resolution indicate that the deformations in the fault zones paradoxically deviate from the movements inherited from the previous geological epochs. The paradoxes of high and low deformation rates in recent geodynamics lie in the reliably established empirical fact that extremely high local deformation rates (up to 10?5 per annum and higher) exist in the fault zones in the setting of weak regional deformations, whose annual rates are by two to three orders of magnitude lower. Very low annual average rates of relative horizontal deformations, which only measure 3–5 amplitudes of tidal deformations of the solid Earth, are revealed in the seismically active regions of Kopet Dag and Kamchatka as well as in the San Andreas Fault Zone in northern California. The fault-block dilemma arising in the interpretation of the observations of recent fault geodynamics is formulated. Either the role of active element, which forms the present anomalous deformations, is played by a block, while a fault plays the role of the passive element, or the fault zone itself is a source of anomalous movements, while the blocks are passive elements (hosting medium). It is shown that paradoxes of low and high deformation rates vanish if we assume that the recent anomalous geodynamics is formed by parametric excitation of the deformation processes in the fault zones in the conditions of quasi-static loading. 相似文献
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L. P. Korsunova V. V. Khegai Yu. M. Mikhailov S. E. Smirnov 《Geomagnetism and Aeronomy》2013,53(2):227-233
The data of hourly measurements of ionospheric parameters in Petropavlovsk-Kamchatsk are analyzed for the period 1998–2002. In the vertical component of near-surface atmospheric quasistatic electric field Ez, earthquake precursors in the form of anomalous negative bays have been found earlier. In some cases, anomalously high sporadic layer Es, interpreted as an ionospheric precursor of an earthquake, was observed simultaneously with anomalous negative bays in Ez. All these cases were correlated with earthquakes of different magnitudes which occurred with a significant time delay (more than five days) after the precursor appearance. Based on the whole data set (including those for simultaneously measured Es and Ez), empirical dependences linking the prediction time of a precursor, earthquake magnitudes, and the distance from the observation point to the epicenter, are presented. It is shown that these dependences are close to those obtained earlier for long-term earthquake precursors in near-surface geophysical fields of the same seismoactive region. Estimates of the prediction time for earthquake precursors on the boundaries of preparation zones are presented. 相似文献
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利用重、磁和天然地震资料对中南地区进行了综合地质地球物理研究.根据研究区的重、磁异常的分布特征,可将其分为4个重力异常区、3个航磁异常区.根据重力资料反演计算得到的研究区的地壳厚度在295～41 km之间,总的趋势为西厚东薄,地壳厚度与地形起伏基本上呈镜像关系.根据磁力资料计算得到的研究区居里界面在12～40 km之间变化.地震层析成像结果表明研究区内的速度分布总体上体现了纵横交错的断块特征.在纵向尺度上,江汉－洞庭盆地以及周缘造山带的上地壳结构变化不大,中地壳和下地壳则普遍受到现今构造活动的改造,以致岩石的结构发生了一定的变化.它们主要表现为低速区域的扩大,尤其是在地壳下部尤为突出,这与断陷盆地的拉张以及造山带岩石层的底侵和拆沉作用密切相关.通过对研究区地球物理场的分析计算,在研究区共提取主要断裂带34条.根据岩石层板块大地构造理论,依据岩石层结构、地壳结构和结晶基底等深部结构的不同,将研究区中板内不同构造单元——块体作为一级构造单元,块体之间的深大断裂带作为块体的边界——块体结合带,据此原则在研究区中划分出两个一级构造单元,五个二级构造单元. 相似文献
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The very low frequency-electromagnetic (VLF-EM) technique was used to delineate two sub-parallel lava tubes, faults and dikes
in Umm El-Quttein area, NE Jordan. The investigation of the lava tubes was conducted through 22 VLF-EM profiles across lava
strike; the length of profiles ranged from 700 to 1700 m. The lava tubes outcrop at two sites: Azzam cave and Al-Howa tunnel,
characterized by slightly weathered basalt, columnar joints and fissure zones; qualitative interpretation of Fraser and Karous-Hjelt
maps differentiate those zones as linear, elongated and circular anomalous zones. The 2-D tipper inversion of VLF-EM data
and resistivity imaging had the potential to screen out three anomalous zones of likely resistivity contrast: the lava tube
body with resistivity over 2500 Θ·m, the fractured zones with resistivity less than 500 Θ·m, and the host vesicular basalt
with resistivity of 1500 Θ·m. The strike of lava tubes varied from SW to NE direction with depth less than 20 m and width
from 10 to 30 m. 相似文献
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强震前中短期地震活动异常动态图像的表示方法及其预测意义 总被引：4，自引：0，他引：4
提出了二个描述中强震发生前中短期阶段地震活动异常时空演经图像的参量σＮ、σＥ。分别将其用于华北地区、新疆地震区及南北地震带,并对其预报效能进行检验,对其异常的空间分布图像与强震发生地震进行了分析,结果表明,该二参量能较好地瓜倾吐夺前中短期阶段孕震区及其周围地区地震活动的异常平静及丛集的现象。二参量异常的时空分布图像上示出在中强震发生前３个月至１年在震中周围地区有明显的异常分布,且随着时间逼近发震时 相似文献
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北黄海盆地是我国近海海域尚未取得油气勘探突破的盆地之一.在海洋环境中应用海底油气藏的烃渗漏现象寻找油气有利区具有良好应用前景,为了给该区的含油气远景评价及下一步油气勘探缩小靶区提供地球物理依据,本文利用磁法这一经济、有效的油气渗漏异常地球物理判别手段,开展了识别海底烃渗漏引发磁异常的方法研究.给出一种根据“有导师”的模式识别技术,在充分利用磁异常多种数值特征及纹理特征的基础上,提取烃渗漏蚀变带磁异常的方法.通过已知约束信息（如见油井位等）的点、线、面三种基元及其邻近数据网格点组成基类,将其提取的模式或特征向量作为待识别异常匹配或学习的模板,利用加权欧氏距离函数计算待识别异常特征向量与模板向量之间的相似性,进行模式匹配,从而识别出与模板相似程度较高的异常.应用此方法圈定了北黄海盆地的烃渗漏“磁亮点”分布,从“磁亮点”异常区与中生代地层的分布以及地球化学异常（低层大气烃类检测和海底微生物异常）的对应情况来看,表明该识别方法是识别烃渗漏弱磁异常的一种有效手段.对研究区构造特征、磁异常及地球化学异常特征的综合分析表明,位于北黄海研究区东部和北部的“磁亮点”异常区可能是北黄海盆地较好的含油气远景区. 相似文献
9.
Stein Kjetil Helle Noralf Rye Bjrg Stabell Lisbeth Prsch-Danielsen Christer Hoel 《Journal of Geodynamics》2007,44(3-5):96-128
The Younger Dryas (YD) maximum highstand shoreline in SW Norway has traditionally been considered as being slightly concave, gradually steepening in the direction of uplift. This phenomenon is attributed to geoidal and isostatic effects near the former ice-sheet margin. On the basis of isolation basin data from the region, we have reconstructed this shoreline, and a Bølling-Allerød (B-A) lowstand shoreline, along three profiles in SW Norway. Along all profiles there are shore levels which, within the error limits estimated, cannot be captured by a single straight (or curved) shoreline. The anomalous shore levels occur near major fault zones and are interpreted to reflect differential uplift rates on opposite sides of faults, superimposed on the general glacio-isostatic tilting of the region. The inferred faulting is consistent with observations previously reported as neotectonic ‘claims’ in the region and shed new light on the deformational structures observed in seismic profiles of the fjord sediments. Excluding the anomalous shore levels, a straight shoreline with gradient ca. 1.1 m/km provides the best and most consistent representation of the YD shore levels along the three profiles. The B-A lowstand shoreline is constrained by fewer data points, but is approximately parallel-dipping the highstand shoreline. Our reconstructions imply a less steep YD maximum highstand shoreline compared to previous reconstructions, where gradients up to 1.4 m/km have been inferred. This may imply that the ice load effect on the lithosphere in SW Norway during the YD is less than previously assumed. 相似文献
10.
Analysis of vertical sounding data obtained on the network of domestic stations equipped with Parus-A ionosondes has shown that anomalous reflections from the ionosphere previously detected in Moscow are observed throughout the whole mid-latitude region. It is shown that the longitudinal effect impacts the probability of the appearance of anomalous reflections. Their spatiotemporal scales are determined. The horizontal dimensions of the anomalies, as a rule, range from several tens to several hundred, possibly a thousand, kilometers. The region of altitudes at which anomalous reflections are observed extends from the E region to F2 layer. The frequency range in which they are most often recorded is from 2 to 14 MHz. The time of their existence ranges from a fraction of minutes to many hours. 相似文献
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综合多种前兆方法分析地震活动规律,研究目标地区未来地震发生的趋势。首先采用图像信息法(PI)进行扫描,从长期尺度上找出研究区域内地震活动异常的地区,并结合相关的活动断裂分布及区域地震活动确定未来地震的发震危险区;然后采用加卸载响应比(LURR)、态矢量(SV)、矩张量加速释放(AMR)等中短期前兆方法分析这些区域的地震发生可能,并对地震发生的相关信息做进一步估算;在空间上实现向地震危险区域的逐渐逼近,时间上实现从长期预测到中短期预测的自然过渡。作为回顾性震例研究,我们对近3年来发生在中国西部的强震(ML6.5)进行了检验,结果表明,相对于单一算法而言,将不同前兆方法适当组合结合能够更为明确地为未来地震危险性评估提供信息和约束。 相似文献
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《Advances in water resources》1999,22(6):633-644
Large deformations that accompany longwall mining result in complex spatial and temporal distributions of changes in undrained pore fluid pressures around the advancing face. These seemingly anomalous changes are recorded in the rapid water level response of undermined and adjacent wells, and may be explained in the short-term as a undrained poroelastic effect. A three-dimensional finite element model is applied to define anticipated pore fluid response both around the advancing mining face, at depth, and in the near surface region. The results are carefully verified against the response recorded at three well-instrumented longwall sites. Pore pressure changes are indexed directly to volumetric strains defining zones of significant depressurization in the caving zone and in zones of extension adjacent to the subsidence trough on the ground surface. Overpressurization occurs in the abutment region, at panel depth, and in the surface compressive zone immediately inside the angle-of-draw. These results are confirmed with available, short-term water level response data, defining the strongly heterogeneous spatial response and the significance of well depth on anticipated water level response. 相似文献
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The paper presents results of analysis of spatiotemporal variations in the rigidity of seismically active rock masses obtained from California Integrated Seismic Network data on first arrivals of P waves from local background (M < 5.0) earthquakes. The main goal was to determine sizes of zones of an anomalous response to the nucleation of strong earthquakes and to reveal specific features of dynamic manifestations of anomalies in crustal fault zones. As a result, conclusions are drawn on the nature of the variations, their implications for the development of strong earthquake sources, and their suitability for earthquake prediction. 相似文献
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A geophysical investigation of a hot spring system located in Rabulu, Fiji, was carried out from October 2014 to March 2015. The investigation covered a survey area of 6075 m2. Self-potential (SP), ground temperature and soil carbon dioxide (CO2) concentrations were measured and investigated for their distribution characteristics and inter-linkages. Results indicated obvious anomalous zone at the hot spring discharge site. The SP profile analysis highlighted thermal water upwelling zones and elevation-driven subsurface groundwater pathways. Measurement of subsurface temperatures up to 1 m depths revealed increasing temperatures, indicating potentially high thermal gradients in the area. Surface soil CO2 distributions also agreed with SP and ground temperature results. The overall result of the study demonstrated that synchronised measurements of SP, ground temperature and soil CO2 can be instrumental in identifying anomalous zones near the hot spring sites. Other parameters such as spring water temperature, discharge rate and energy flux estimates from the spring were calculated and analysed. The high-dense multi-parameter data coverage allowed interpretation of geothermal features at a scale never conducted in Fiji before. The near-surface investigations reported in this study corroborate previously suggested steady geothermal activity in the region, deserving further detailed investigation. 相似文献
17.
Wang Ruobai 《中国地震研究》2005,19(3):327-337
INTRODUCTIONThe Zhangjiakou-Penglai fault zone has drawnextensive attentionfromseismologists and geologistssince it was determinedinthe1980’s(Zheng Binghua,et al.,1981).Ma Xingyuan,et al.(1989)consideredit asthe north boundaryof North China sub-block.Int… 相似文献
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Cross-hole imaging method using Time Domain (TD) and Frequency Domain (FD) parts of cross-hole radar tomography data acquired using Step Frequency Ground Penetrating Radar (SFGPR) was implemented. This method was adopted for imaging foundation of a dam to check if the foundation was free of geological weak zones. The dam site is characterised by massive and jointed-phyllites associated with major and minor shears. The cross-hole radar tomography data was acquired in the frequency bandwidth of 250 MHz, from the deepest level gallery up to a depth of 40 m in the foundation. In TD, first arrival time and amplitudes of radio waves were inverted using Simultaneous Iterative Reconstruction Technique (SIRT) resulting in velocity and attenuation tomograms. The tomograms showed nearly uniform velocity or attenuation structure in the respective tomographic plane. Subsequently, cross-hole radar tomography data was analysed in FD for a variation of spectrum-amplitude at different frequencies. Amplitudes picked at each single frequency were then inverted using SIRT for obtaining frequency domain attenuation tomogram (FDAT). The FDAT clearly showed presence of anomalous high attenuation zones in the depth range of 23–33 m of the tomographic plane. The anomalous zones in the attenuation tomogram are weak zones in the foundation. To validate the above observations, cross-hole seismic tomography was also done in the same boreholes. Cross-hole seismic tomography results showed low velocity (p-wave) zones around the same location corresponding to the high attenuation zone in FDAT, bringing the dormant weak zone to light. This enabled fine-tuning of the reinforcement design and strengthening the weak zone. This paper discusses the cross-hole radar tomography imaging method, the results of its application in imaging weak zones in the foundation and the comparison of cross-hole radar tomography results (in TD and FD) with the cross-hole seismic tomography results. 相似文献
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地壳中流体动力学模型研究 总被引：4，自引：0，他引：4
较全面介绍了近年国内外地壳地下流体动力学研究的最新成果。综合分析前人研究成果并将其系统化为地完尺度上地下流体动力学系统的概念模型和数学模型。模型根据影响地下流体动力特性的主要因素和介质渗透特征,把地壳渗流场分为深度小于6km的饯部带、6～17km的过渡带和大于17km的深部带。数学处理上把驱动流体运动的各种地质作用归一化为“地质力”,以地下流体运动方程中的源汇项表示。分析了不同地质环境各种地质作用对地下流体系统的作用特征。对地壳中普遍存在的异常孔隙压力现象,从流体动力学的角度进行了解释,并认为周期性地震活动是形成异常高孔隙压力的主导因素。 相似文献