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1.
在假设临汾水准两次巨幅形变异常为断裂错动的情况下,基于矩形断层位错模型模拟了罗云山断裂（土门-峪里段）错动所引起的垂直形变场分布,并通过D-InSAR技术对研究区域内的地面形变场进行实测,分析结果表明：（1）断裂错动理论上可导致长轴与断裂走向平行的椭圆状变形区域,位于断裂上盘的区域中心变形量最大,变形量向外围逐渐衰减为零,两次错动导致的变形波及范围分别约为长轴18Km和26Km,短轴12Km和17Km,显著变形幅度分别约为1-3mm和4-14mm。（2）D-InSAR实测形变场显示两次异常期间研究区域内未发现与断裂走向一致的连续变形区域,仅在盆地内部存在可能由于过量开采地下水所导致的地面沉降,变形范围约为10-12mm和10-15mm。（3）实测形变场与理论形变场在变形区域和变形幅度上均不一致,说明断裂活动引起临汾水准巨幅形变的可能性不大,可能为断裂上盘的土层局部变形所致。（4）通过断层位错模型的理论模拟和D-InSAR技术的实际监测相结合可以有效地确定跨断层水准巨幅形变异常的性质,为重大水准异常核实提供科学依据。 相似文献
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J.M. Maillol M.-K. Seguin O.P. Gupta H.M. Akhauri N. Sen 《Geophysical Prospecting》1999,47(2):103-116
The history of subsidence, fires, flooding and other kinds of environmental hazards related to shallow coal workings in India goes back to colonial times some 300 years ago. As coal production accelerated in modern times, so did the environmental and socio-economic drawbacks related to exploitation. In the mid-1980s, a hydropneumatic sand-stowing method was developed to fill in abandoned galleries but their exact location had to be known. Unfortunately, most of these old workings are uncharted and consequently large tracts of land cannot be stabilized. A research programme making use of integrated surface, borehole and cross-hole geophysical methods was undertaken over a five-year span to try to solve this problem. Surface geophysical methods, being cheaper and faster than their cross- and downhole counterparts, were used to cover larger areas on an exploratory basis, while cross-hole methods were employed to locate more accurately one or a network of galleries to be perforated by drillhole(s) and used as a conduit for sand stowing. We report the results of one of the cross-hole geophysical methods: electrical resistivity tomography (ERT). A pole–dipole configuration is used and both cross-hole and surface-borehole methodologies are tested. Forward modelling and inversion of synthetic data making use of downhole and surface physical and geometrical parameters are presented first. This phase is followed by the inversion of real data. It is concluded that ERT is not applicable for the detection of dry voids, but is effective in a waterlogged environment which is estimated to represent 85–90% of the cases. In waterlogged galleries, ERT is applicable in both cross-hole and surface-downhole modes, the latter allowing a larger surface coverage at low cost. ERT is thus a reliable geophysical tool to image water-filled voids and an adequate technique to address environmental and geotechnical problems. 相似文献
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As part of the effort to assess the seismic hazards of Singapore and the Malay Peninsula, representative ground motion prediction models have to be established. Seven existing attenuation relationships developed for shallow crustal earthquakes in stable continent and active tectonic regions are examined, and they are found to consistently over‐predict the ground motions of Sumatran‐fault earthquakes recently recorded in Singapore. This may be attributed to the differences in the regional crustal structures and distance ranges considered. Since the number of recorded ground motions in the region is very limited, a new set of attenuation relationships is derived based on synthetic seismograms. The uncertainties in rupture parameters, such as stress drop, focal depth, dip and rake angles, are defined according to the regional geological and tectonic settings as well as the ruptures of previous earthquakes. Ground motions are simulated for earthquakes with Mw ranging from 4.0 to 8.0, within a distance range from 174 to 1379km. Besides magnitude and distance, source‐to‐station azimuth is found to influence the amplitudes of the ground motions simulated. Thus, the azimuth is taken as an independent variable in the derived ground motion attenuation relationships. The Sumatran‐fault segments that have the potential to generate a specified level of response spectral accelerations in Singapore and Kuala Lumpur are identified based on the newly derived ground motion models. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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断层岩的粒度分布包含岩石破裂机制、摩擦性质和地震能量分配等重要信息。筛分-称重和激光测量是分析断层岩三维粒度的2种有效方法,但每一种方法的测量范围仅有3个量级,难以全面反映断层岩的粒度分布特征。利用上述2种方法对汶川地震断层滑动带上的断层岩（简称断层岩）的粒度分布进行了测量,粒径测量范围从0.2μm至16mm,跨度达到5个数量级。结果显示：1）存在临界粒径dc（0.95～1.90μm）。粒度大于和小于dc的颗粒满足不同的颗粒数（Nd）-粒径（d）分布关系,表明该断层岩的粒径分布不具有自相似性特征。2）利用粒度大于dc的颗粒计算出的分形维数与断层岩类型有很好的相关性,即断层带边缘的角砾岩的平均分形维数为2.6,核部压碎角砾岩的平均分形维数约为3.0,中心断层泥的分形维数约为3.5。粒径小于dc的颗粒的分形维数为1.7～2.1。分形维数的突变反映出断层破裂机制的复杂性,即在不同的粒度域,岩石的破裂机制不尽相同。3）依据粒度分析结果,估算出汶川地震断层泥的单位破裂能（Es）为0.63MJ/m2。 相似文献
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Seismic measurements of the internal properties of fault zones 总被引：1，自引：0，他引：1
The internal properties within and adjacent to fault zones are reviewed, principally on the basis of laboratory, borehole, and seismic refraction and reflection data. The deformation of rocks by faulting ranges from intragrain microcracking to severe alteration. Saturated microcracked and mildly fractured rocks do not exhibit a significant reduction in velocity, but, from borehole measurements, densely fractured rocks do show significantly reduced velocities, the amount of reduction generally proportional to the fracture density. Highly fractured rock and thick fault gouge along the creeping portion of the San Andreas fault are evidenced by a pronounced seismic low-velocity zone (LVZ), which is either very thin or absent along locked portions of the fault. Thus there is a correlation between fault slip behavior and seismic velocity structure within the fault zone; high pore pressure within the pronounced LVZ may be conductive to fault creep. Deep seismic reflection data indicate that crustal faults sometimes extend through the entire crust. Models of these data and geologic evidence are consistent with a composition of deep faults consisting of highly foliated, seismically anisotropic mylonites. 相似文献
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中国地壳运动观测网络1000个观测站的GPS非连续观测区域网分别在1999年、 2001年、 2004年、 2007年和2009年作了5次观测。 2008年5月12日汶川8.0 级地震震中(31.0°N, 103.4°E)恰好在区域网GPS观测站密集的地区。 区域网长期、 多期GPS观测可降低年周期变化影响, 有利于获取此次地震前后的垂直位移趋势变化。 简要讨论了GPS垂直位移观测的精度。 分析了垂直位移观测的主要干扰地面沉降, 特别是华北地区因大量抽取地下水产生的严重地面沉降。 为获取汶川地震前垂直运动信息, 首先剔除因大量抽取地下水产生的大幅度沉降干扰结果, 通过趋势面分析中国大陆垂直位移空间分布, 显示了3个垂直位移沉降最显著区域。 对比分析表明, 临近汶川震区的沉降区, 未见大量抽取地下水干扰影响。 汶川地震前1999—2007年区域网GPS观测站得到的垂直位移表明, 汶川地震紧临显著沉降区的西北侧, 龙门山断层北段垂直运动闭锁。 该沉降区与另两个沉降区的时空变化明显不同, 也与区域网水平应变异常区的空间分布不同, 但该沉降区与区域网水平应变异常区同时出现。 大幅度同震垂直位移集中在龙门山断层北段震前垂直位移闭锁区。 这些事实表明, 汶川地震前GPS观测到的紧临震中的沉降区及垂直运动闭锁区与汶川地震的发生存在密切关系。 相似文献
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断裂带气体地球化学特征与形变特征之间的相关关系是建立具有物理预报思路断层气流动观测网络布设的重要课题。选择有大量温泉出露点且形变较剧烈的西秦岭北缘断裂带为研究对象,对跨断层形变测量场地进行断层土壤气剖面重合布设及现场测量,重点研究断层气分段性特征与断层形变、地震活动性特征耦合关系,探讨利用多种方法开展断裂带强震危险性分析的可能性。结果表明:断裂带土壤气地球化学特征和断层水准形变特征的分布具有良好相关关系,二者对比结果同时显示出西秦岭北缘断裂带中东段——武山段断层活动性相对活跃,渭源—漳县段次之,天水段断层相对闭锁的特征;且武山和甘谷走滑拉分区因流体活动的影响以中小地震活动为主,天水段和漳县段西部及与武山段交汇的盘古川地区,流体活动较弱,应变速率较小,存在孕育强震的可能。 相似文献
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—The interpretation of the results of regional and local leveling which began in 1977 in the Mexicali Valley and the local short profile precision leveling which started in 1994 are discussed. The relation of vertical deformations around the Cerro Prieto Geothermal Field (CPGF) and along the Imperial fault, with local tectonics and seismicity in the Mexicali Valley, is reviewed. Also the relation between vertical deformation and fluid operation in the CPGF is analyzed. The subsidence observed in the field seems to be induced by fluid extraction. The way in which fluid production influences surface changes along the Imperial fault is not clear. The possibility that seismicity is triggering subsidence in the area and vertical movement on the Imperial fault is discussed. 相似文献
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V. V. Ruzhich 《Izvestiya Physics of the Solid Earth》2009,45(11):987-995
The paper presents the results of long-term geological-geophysical studies of the author, which have a direct relationship
to the structure and development of the sources of the strong earthquakes that occurred on the territory of Mongolia and the
Baikal rift zone. They left imprints in the form of seismic dislocations in the near-surface layers or in the form of thermally
treated rocks (pseudo-tachylites), considered as evidence of the manifestation of seismogenic motions in the segments of seismoactive
faults at depths of 10–20 km. It was revealed that in the regions of the manifestation of denudation shear on the Earth’s
surface with a length of many kilometers it is possible to identify the deep fragments of faults, in which previously the
signs of rapid seismogenic motions along the faults had been manifested. Such deep fragments are revealed from the presence
of friction planes, covered by the finest glass films, which arose under the strong frictional heating of rocks before the
stage of melting. In this way, the possibility of studying such sections of zones of seismo-generating faults is validated,
considering them as deep fragments of earthquake sources, which occurred many million years ago.
New information on the instrumental measurements of the velocity of motions in the seismoactive faults is also discussed in
the work. The ideas on the mechanisms of generating seismic vibrations in the fault zones are presented. The conclusion that
the lower segments of faults in the source regions of earthquakes are capable of penetrating rapidly at depths of 25–40 km,
where the viscoplastic deformations of rocks predominate, causing their nonlinear behavior, is substantiated. On the development
of the new models of earthquake sources, more adequate to geological conditions, it is expedient to consider the ideas presented
in the paper 相似文献
13.
Burbey TJ 《Ground water》2008,46(2):202-211
A 62 day controlled aquifer test was conducted in thick alluvial deposits at Mesquite, Nevada, for the purpose of monitoring horizontal and vertical surface deformations using a high-precision global positioning system (GPS) network. Initial analysis of the data indicated an anisotropic aquifer system on the basis of the observed radial and tangential deformations. However, new InSAR data seem to indicate that the site may be bounded by an oblique normal fault as the subsidence bowl is both truncated to the northwest and offset from the pumping well to the south. A finite-element numerical model was developed using ABAQUS to evaluate the potential location and hydromechanical properties of the fault based on the observed horizontal deformations. Simulation results indicate that for the magnitude and direction of motion at the pumping well and at other GPS stations, which is toward the southeast (away from the inferred fault), the fault zone (5 m wide) must possess a very high permeability and storage coefficient and cross the study area in a northeast-southwest direction. Simulated horizontal and vertical displacements that include the fault zone closely match observed displacements and indicate the likelihood of the presence of the inferred fault. This analysis shows how monitoring horizontal displacements can provide valuable information about faults, and boundary conditions in general, in evaluating aquifer systems during an aquifer test. 相似文献
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当前强震后铁路路基变形预测中,相关算法未能考虑激活函数的非线性属性,造成非线性变形特征数据提取不完整,且其特征数据存在偏差,陷入局部最优解。文章提出BP神经网络算法考虑激活函数后对强震路基塌陷变形预测方法,采用双极S因子补偿ReLU非线性激活函数,优化BP神经网络算法,解决非线性路基变形特征数提取问题。利用数据标准化归一方法,对已修正提取的全部变形特征数据进行偏差数据归一,得到路基变形特征数据集合,结合强震后路基变形连接权值计算路基变形预测值,完成强震路基塌陷变形预测。结合实测结果,在matlab下进行预测实验,结果表明所提混合方法可以有效地对水平地震作用下铁路路基塌陷变形程度进行预测,且预测值在误差允许范围内,为铁路的安全运行以及实时维护提供重要依据。 相似文献
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由现今小震资料研究琼北地区区域应力场和发震构造 总被引：2，自引：1，他引：1
利用2000年以来海南地震台网记录的琼北地区的波形资料,采用双差法对103个地震进行重新定位,采用振幅比方法测定震源机制.在此基础上,反演了琼北地区的区域应力场,由震源位置拟合出两个震源断层面,并且计算在区域应力场作用下的滑动方式.对照历史大震的等震线,WNW走向的震源断层位于极震区中部稍偏东的地方,与等震线长轴方向相同,表明该震源断层是1605年琼山大震的发震构造;高倾角震源断层的北东盘向东南斜下方滑动,对于该盘NNW象限产生强烈拉张,以致出现罕见的陆陷成海现象.另外一条NS向震源断层恰好位于第四系火山岩和第四系盆地交界处,是区域升降运动最为强烈的地方,正断层类型的震源断层东盘下降,与沉积盆地一致.研究表明由现今小震反演的两条震源断层分别与历史大震及构造运动有关,而与浅表断裂并不重合,存在深浅构造不协调的现象. 相似文献
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The Datong Basin is located to the north of the Fenwei Graben Basin, where ground fissures and subsidence are common geological hazards. The Datong Basin is also one of China's main energy bases and is known as “the hometown of coal”. In this study, the small baseline subset InSAR technique was used to process 40 scenes of Envisat ASAR images that cover this area. The magnitude and distribution of subsidence in the Datong Basin were obtained. Additionally, the relationships among the regional land subsidence, ground fissures and fault activity were addressed. The results reveal that Datong ground subsidence is affected by the groundwater exploitation and the nearby faults. The Datong ground fissures are controlled by regional fault activity (e.g., seismic activity) and its interaction with the ground subsidence. Meanwhile, the influence of surface precipitation on ground fissure activity was analyzed. The differential subsidence on both sides of the ground fissures was also studied. 相似文献
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地震断裂带的孕震环境对于研究地震的发生至关重要.本文以汶川地震断裂带科学钻探2号（WFSD-2）钻孔岩心中的假玄武玻璃、碎裂岩及其围岩为研究对象,通过岩石磁学测试,并结合显微结构观察探讨龙门山断裂带大地震的孕震环境.WFSD-2岩心碎裂岩中的假玄武玻璃是龙门山断裂带曾经发生过大地震活动的岩石学证据,假玄武玻璃具有高磁化率特征,而碎裂岩的磁化率值与围岩相似,假玄武玻璃中的新生磁铁矿是其高磁化率值异常的重要原因之一.假玄武玻璃中较少量的新生磁铁矿暗示了假玄武玻璃的生成环境为含氧量较低的高温还原环境.大地震断裂的摩擦热是改变龙门山断裂带中假玄武玻璃岩石磁学特征的主导因素,流体作用较弱.无高磁化率异常的碎裂岩经历的温度小于300℃,推测假玄武玻璃的生成深度较深.WFSD-2岩心中20余层假玄武玻璃脉体证明映秀—北川断裂带是一条长期活跃的断裂带,龙门山断裂带上曾经发生了多次大地震断裂活动,这些大地震可能发生在深度较大、流体作用较弱的还原性孕震环境中. 相似文献
18.
THREE-DIMENSIONAL DEFORMATION OF THE 2008 GAIZE EARTHQUAKES RESOLVED FROM INSAR MEASUREMENTS BY MULTIPLE VIEW ANGLES AND ITS TECTONIC IMPLICATIONS 
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下载免费PDF全文 The 2008 Gaize MW6.4 earthquake,occurring on the tensional active fault zone located between Lhasa terrane and Qiangtang terrane in the interior of Tibet is a typical normal-faulting event.In this paper,we resolve the three-dimensional coseismic displacement fields of the earthquakes using a least-square iterative approximation solution with a priori knowledge,according to the theoretical basis that InSAR measurements are extremely insensitive to N-S component.Results show that the boundary dividing the two sides of the main-shock fault is very clear in the vertical movement,and two remarkable subsidence centers can be observed on the hanging wall,while amplitude of the west one (-48.9cm) is larger than the east (-41.4cm),but the maximum uplift on the footwall is only 5cm.In addition to some northward movement with amplitude less than 5cm around the aftershock fault,the north-south deformation field suggests an overall southward movement.The three-dimensional results indicate that the induced surface movement is predominantly vertical and mostly occurred on the upper side,while there are obvious east-west separation and eastward rotation in the horizontal plane.The full vectors are consistent with simulated deformation field with the RMSE less than 6cm,so the research demonstrates the feasibility of the method to recover precise three-dimensional deformation field.On the whole,the three-dimensional deformation field coincides with the tensile fracture characteristics of Gaize earthquakes,and the tectonic stress background of coeval east-west extension and north-south shortening. 相似文献
19.
用双差定位结果分析华北地区的地震活动 总被引：6，自引：0，他引：6
华北地区北部是阴山—燕山隆起区、 华北平原和太行山隆起的交界处, 区域内地震活跃, 北部有张家口—渤海地震活动带(张渤带), 西邻山西地震活动带。 本研究采用双差定位法对华北地区2006—2009年发生的地震进行重新定位, 结果显示, 近年来华北地区的地震主要集中在北部的张渤带上, 总体呈WNW向分布。 震源深度主要集中在0~20 km的中上地壳, 占地震总数的96.3%, 有大约57.5%的地震分布在10 km以上的地壳内。 张渤带东部的唐山地区是该地震带上地震最密集的地区, 地震分布与区域内的断层有密切关系。 华北平原中南部的邢台地区也是地震相对较密集的区域, 定位结果显示, 邢台地区的新河断裂可能深达Moho面, 在该断裂的下方可能存在速度异常体, 把邢台地区西南部的地震活动从空间上隔离成上下两部分。 沿新河断裂的地震分布出现异常, 在深度10 km处, 地震分布由北东向西南逐渐与上部的地震分离, 震源深度逐渐加深, 最深可达30 km左右。 相似文献
20.
Katharina Anders Sabrina Marx Julia Boike Benjamin Herfort Evan James Wilcox Moritz Langer Philip Marsh Bernhard Höfle 《地球表面变化过程与地形》2020,45(7):1589-1600
This paper investigates different methods for quantifying thaw subsidence using terrestrial laser scanning (TLS) point clouds. Thaw subsidence is a slow (millimetre to centimetre per year) vertical displacement of the ground surface common in ice-rich permafrost-underlain landscapes. It is difficult to quantify thaw subsidence in tundra areas as they often lack stable reference frames. Also, there is no solid ground surface to serve as a basis for elevation measurements, due to a continuous moss–lichen cover. We investigate how an expert-driven method improves the accuracy of benchmark measurements at discrete locations within two sites using multitemporal TLS data of a 1-year period. Our method aggregates multiple experts’ determination of the ground surface in 3D point clouds, collected in a web-based tool. We then compare this to the performance of a fully automated ground surface determination method. Lastly, we quantify ground surface displacement by directly computing multitemporal point cloud distances, thereby extending thaw subsidence observation to an area-based assessment. Using the expert-driven quantification as reference, we validate the other methods, including in-situ benchmark measurements from a conventional field survey. This study demonstrates that quantifying the ground surface using 3D point clouds is more accurate than the field survey method. The expert-driven method achieves an accuracy of 0.1 ± 0.1 cm. Compared to this, in-situ benchmark measurements by single surveyors yield an accuracy of 0.4 ± 1.5 cm. This difference between the two methods is important, considering an observed displacement of 1.4 cm at the sites. Thaw subsidence quantification with the fully automatic benchmark-based method achieves an accuracy of 0.2 ± 0.5 cm and direct point cloud distance computation an accuracy of 0.2 ± 0.9 cm. The range in accuracy is largely influenced by properties of vegetation structure at locations within the sites. The developed methods enable a link of automated quantification and expert judgement for transparent long-term monitoring of permafrost subsidence. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献