汶川地震震中映秀地区地表破裂特征   总被引：4，自引：3，他引：1       下载免费PDF全文

马博琳  李勇  董顺利  陈浩  闫亮  乔宝成 《地震工程学报》2009,31(4):339-343

汶川8级大震的震中位于映秀镇,地震在映秀地区造成了多处地表破裂,如公路拱曲、地震陡坎,坡中槽新变形等,长度达300余米.经实地全站仪和GPS测量,定量分析了地表破裂的垂直分量与水平分量以及两者之间的比值,以此揭示了映秀-北川断裂的运动性质为逆冲兼右行走滑,在映秀地区逆冲分量大于走滑分量.将本次地震造成的位错数据与震前资料对比,发现汶川地震产生的地表破裂位置与地质历史上映秀-北川断裂造成的断层位错位置是相当吻合的,说明映秀地区Ⅳ级阶地上40余米的的断层陡坎可能是地质历史时期若干次大地震的结果.  相似文献   

Development and verification of a 3-D integrated surface water–groundwater model     

Katerina Spanoudaki  Anastasios I. Stamou  Aikaterini Nanou-Giannarou 《Journal of Hydrology》2009,375(3-4):410-427

Coupled modelling of surface and subsurface systems is a valuable tool for quantifying surface water–groundwater interactions. In the present paper, the 3-D non-steady state Navier–Stokes equations, after Reynolds averaging and with the assumption of a hydrostatic pressure distribution, are for the first time coupled to the 3-D saturated groundwater flow equations in an Integrated suRface watEr–grouNdwater modEl (IRENE). A finite-difference method is used for the solution of the governing equations of IRENE. A semi-implicit scheme is used for the discretisation of the surface water flow equations and a fully implicit scheme for the discretisation of the groundwater flow equations. The two sets of equations are coupled at the common interface of the surface water and groundwater bodies, where water exchange takes place, using Darcy’s law. A new approach is proposed for the solution of the coupled surface water and groundwater equations in a simultaneous manner, in such a fashion that gives computational efficiency at low computational cost. IRENE is verified against three analytical solutions of surface water–groundwater interaction, which are chosen so that different components of the model can be tested. The model closely reproduces the results of the analytical solutions and can therefore be used for analysing and predicting surface water–groundwater interactions in real-world cases.  相似文献   

连通域标识法在FMI图像溶洞信息定量拾取中的应用          下载免费PDF全文

闫建平  梁强  李尊芝  耿斌  寇小攀  扈勇 《地球物理学报》2016,59(12):4759-4770

溶蚀孔洞在碳酸盐岩储层中是重要的流体储集空间,研究成像测井(FMI)图像孔洞连通域标记及信息定量拾取很有意义.全井眼微电阻率成像测井(FMI)经数据处理后可得到全井壁高分辨率的彩色图像,经图像灰度化、中值滤波处理后,通过阈值分割得到能够反映井壁溶蚀孔洞特征的二值图像,孔洞表现为黑色暗斑.基于等价对处理的图像连通域标记算法具有快速、不重复标记的优点,利用该算法,可准确地从二值图像中标记溶蚀孔洞连通域,进而可对每个连通域进行目标信息拾取,包括孔洞尺寸、连通域面积、圆度等.利用反映溶蚀孔洞发育程度的面孔率曲线对图像进行分层,在此基础上可拾取每一层段溶蚀孔洞面孔率、分选系数及溶洞密度值的分布等非均质信息,能够定量地评价溶蚀孔洞发育、非均质性强的碳酸盐岩储层,也是FMI图像应用于岩石孔洞结构信息定量表征新的尝试.  相似文献   

气候变暖对辽宁西部地面及作物耕作层温度的影响     

张富荣  ;张国林  ;冯雪菲  ;刘志鹏  ;张玉书 《气象与环境学报》2014,30(3):96-99

利用气候倾向率、标准偏差方法,划分基准年研究1952-2010年辽宁西部地面、耕作层温度变化特征。结果表明：辽宁西部年平均地面温度、农作物生长季地面和耕作层温度呈升高趋势,气候倾向率分别为0.395℃/10a、0.304℃/10a、0.206℃/10a。冬季、春季对年平均地面温度升高贡献最大,气候倾向率为0.535℃/10a、0.521℃/10a;夏季、秋季贡献较小,气候倾向率为0.223℃/10a、0.291℃/10a。第Ⅲ基准年升温最剧烈。研究结果可为该地区农业生产结构调整、生态环境治理等提供参考。  相似文献   

An integral-balance nonlinear model to simulate changes in soil moisture,groundwater and surface runoff dynamics at the hillslope scale     

《Advances in water resources》2014

We present a system of ordinary differential equations (ODEs) capable of reproducing simultaneously the aggregated behavior of changes in water storage in the hillslope surface, the unsaturated and the saturated soil layers and the channel that drains the hillslope. The system of equations can be viewed as a two-state integral-balance model for soil moisture and groundwater dynamics. Development of the model was motivated by the need for landscape representation through hillslopes and channels organized following stream drainage network topology. Such a representation, with the basic discretization unit of a hillslope, allows ODEs-based simulation of the water transport in a basin. This, in turn, admits the use of highly efficient numerical solvers that enable space–time scaling studies. The goal of this paper is to investigate whether a nonlinear ODE system can effectively replicate observations of water storage in the unsaturated and saturated layers of the soil. Our first finding is that a previously proposed ODE hillslope model, based on readily available data, is capable of reproducing streamflow fluctuations but fails to reproduce the interactions between the surface and subsurface components at the hillslope scale. However, the more complex ODE model that we present in this paper achieves this goal. In our model, fluxes in the soil are described using a Taylor expansion of the underlying storage flux relationship. We tested the model using data collected in the Shale Hills watershed, a 7.9-ha forested site in central Pennsylvania, during an artificial drainage experiment in August 1974 where soil moisture in the unsaturated zone, groundwater dynamics and surface runoff were monitored. The ODE model can be used as an alternative to spatially explicit hillslope models, based on systems of partial differential equations, which require more computational power to resolve fluxes at the hillslope scale. Therefore, it is appropriate to be coupled to runoff routing models to investigate the effect of runoff and its uncertainty propagation across scales. However, this improved performance comes at the expense of introducing two additional parameters that have no obvious physical interpretation. We discuss the implications of this for hydrologic studies across scales.  相似文献   

利用强震震源机制解资料反演中国大陆及其邻区的形变场模型     

李长军  任金卫  孟国杰  杨攀新  胡朝忠 《地震》2014,34(3):1-12

搜集了1900-2013年间发生在中国大陆及其邻区的震源机制解资料,详细整理了其中的70个7级及以上大震的震源参数、地表破裂带和地表位移资料。根据资料的完整程度将地震分成三类: A类存在地表破裂和地表位移观测资料; B类存在地表破裂资料,但缺少地表位移观测数据;C类缺少地表破裂带和地表位移观测资料。对B类和C类缺少地表位移观测数据的地震,利用三角形模型模拟其位移分布。再根据地表位移分布及地震破裂带与本文使用网格模型之间的位置关系将地震分段。最后,利用分段前、后的地震数据和改进的双三次样条方法反演研究区域的形变场模型。结果表明:①大震资料的分段处理改进了地震数据的反演结果,提高了反演模型的合理性和空间一致性;在喜马拉雅断裂带,形变场具有更好的连续性,其变形特征与地质等数据的反演结果基本吻合;塔里木盆地和阿尔金断裂的形变量减小,与该区域较低的地震活动性一致;戈壁一阿尔泰的变形从SE的挤压和NE的拉张调整到NE的挤压和NW的拉张;鄂尔多斯西缘的拉张分量明显减小。②113年的地震资料解释了印度板块向欧亚板块运动总速率的30~50%,存在20 mm/a左右的速度亏损,该亏损量可能包括断层蠕动、褶皱等非震形变,未监测到或者缺失的地震,及以弹性应变能形式存在通过潜在地震释放的应变  相似文献   

利用GPS与GRACE监测陆地水负荷导致的季节性水平形变：以喜马拉雅山地区为例   总被引：4，自引：4，他引：0       下载免费PDF全文

王林松  陈超  邹蓉  杜劲松  陈晓东 《地球物理学报》2014,57(6):1792-1804

地表陆地水负荷变化是引起重力场和地壳形变呈现季节性特征的主要因素,并且能够利用地表及空间大地测量技术对其进行有效的监测.本文通过对质量负荷形变效应的理论模拟,描述了水平分量的形变指向以及垂直与水平分量的幅值比可以提高对负荷区域的辨别程度,并且联合GPS坐标时间序列及GRACE模型对喜马拉雅山地区的季节性负荷形变进行了详细对比分析,研究结果显示两者垂直分量的季节性变化具有较好的一致性,且GPS周年项幅值要大于GRACE.而由GRACE解算得到的水平分量结果表明该地区季节性形变主要受东南亚及印度东北部地区的陆地水负荷控制,位于喜马拉雅山地区多数GPS台站的垂直分量及北向分量的初相位与GRACE模型解算结果相近,而部分GPS台站的东向分量与GRACE模型存在明显不同,由此导致GPS与GRACE监测到的形变指向存在差异.通过对GRACE估算精度以及GPS垂直与水平分量幅值比的深入分析,发现GPS对局部周边地区的河流、谷地及农田灌溉等负荷变化造成的形变效应较为敏感,而GRACE由于截断阶次及平滑滤波等影响因素,不仅造成在水平分量上的分辨率远低于垂直分量,而且整体估算精度要低于GPS观测得到的形变信息.  相似文献   

珠江口盆地大地热流特征及其与热岩石圈厚度的关系   总被引：6，自引：4，他引：2       下载免费PDF全文

唐晓音  胡圣标  张功成  杨树春  沈怀磊  饶松  李卫卫 《地球物理学报》2014,57(6):1857-1867

沉积盆地现今热流特征是岩石圈构造-热演化过程的综合反映和盆地热史恢复的必要约束条件,其总体变化趋势与热岩石圈厚度密切相关.本文根据新收集的珠江口盆地19口钻井温度数据,新增计算了19个大地热流数据,其中12个数据位于深水区（水深大于300 m）,丰富了该盆地深水区钻井地热数据.结合前人研究成果,绘制了该盆地的大地热流图,并分析了其热流分布特征.在此基础上通过求解一维热传导方程,计算得到36口井位处的热岩石圈厚度,量化了盆地大地热流与热岩石圈厚度间的关系.结果显示,珠江口盆地大地热流值介于24.2~121.0 mW·m^-2,平均71.8±13.6 mW·m^-2,新增盆地深水区钻井平均热流值高达84.5±4.4 mW·m^-2.大地热流分布整体上从陆架区到陆坡区升高,而热岩石圈厚度整体分布趋势与大地热流相反.大地热流与热岩石圈厚度间存在良好的指数相关性.  相似文献   

中国西部及邻区岩石圈S波速度结构面波层析成像   总被引：7，自引：5，他引：2       下载免费PDF全文

黄忠贤  李红谊  胥颐 《地球物理学报》2014,57(12):3994-4004

本文利用瑞利波群速度频散资料和层析成像方法,研究了中国西部及邻近区域(20°N—55°N,65°E—110°E)的岩石圈S波速度结构.结果表明这一地区存在三个以低速地壳/上地幔为特征的构造活动区域:西蒙古高原—贝加尔地区,青藏高原,印支地区.西蒙古高原岩石圈厚度约为80 km,上地幔低速层向下延伸至300 km深度,说明存在源自地幔深部的热流活动.缅甸弧后的上地幔低速层下至200 km深度,显然与印度板块向东俯冲引起俯冲板片上方的热/化学活动有关.青藏高原地壳厚达70 km,边缘地区厚度也在50 km以上并且具有很大的水平变化梯度,与高原平顶陡边的地形特征一致.中下地壳的平均S波速度明显低于正常大陆地壳,在中地壳20~40 km深度范围广泛存在速度逆转的低速层,这一低速层的展布范围与高原的范围相符.这些特征说明青藏高原中下地壳的变形是在印度板块的北向挤压下发生塑性增厚和侧向流动.地幔的速度结构呈现与地壳显著不同的特点.在高原主体和川滇西部地区上地幔顶部存在较大范围的低速,低速区范围随深度迅速减小;100 km以下滇西低速消失,150 km以下基本完全消失.青藏高原上地幔速度结构沿东西方向表现出显著的分段变化.在大约84°E以西的喀喇昆仑—帕米尔—兴都库什地区,印度板块的北向和亚洲板块的南向俯冲造成上地幔显著高速;84°E—94°E之间上地幔顶部速度较低,在大约150~220 km深度范围存在高速板片,有可能是俯冲的印度岩石圈,其前缘到达昆仑—巴颜喀拉之下;在喜马拉雅东构造结以北区域,存在显著的上地幔高速区,可能阻碍上地幔物质的东向运动.川滇西部岩石圈底界深度与扬子克拉通相似,约为180 km,但上地幔顶部速度较低.这些现象表明青藏高原岩石圈地幔的变形/运动方式可能与地壳有本质的区别.  相似文献   

Retrieval of local surface wave velocities from traffic noise – an example from the La Barge basin (Wyoming)     

M. Behm  Garrett M. Leahy  R. Snieder 《Geophysical Prospecting》2014,62(2):223-243

In regions where active source seismic exploration is constrained by limitations of energy penetration and recovery, cost and logistical concerns, or regulatory restrictions, analysis of natural source seismic data may provide an alternative. In this study, we investigate the feasibility of using locally‐generated seismic noise in the 2–6 Hz band to obtain a subsurface model via interferometric analysis. We apply this technique to three‐component data recorded during the La Barge Passive Seismic Experiment, a local deployment in south‐western Wyoming that recorded continuous seismic data between November 2008 and June 2009. We find traffic noise from a nearby state road to be the dominant source of surface waves recorded on the array and observe surface wave arrivals associated with this source up to distances of 5 kms. The orientation of the road with respect to the deployment ensures a large number of stationary points, leading to clear observations on both in‐line and cross‐line virtual source‐receiver pairs. This results in a large number of usable interferograms, which in turn enables the application of standard active source processing methods like signal processing, common offset stacking and traveltime inversion. We investigate the dependency of the interferograms on the amount of data, on a range of processing parameters and on the choice of the interferometry algorithm. The obtained interferograms exhibit a high signal‐to‐noise ratio on all three components. Rotation of the horizontal components to the radial/transverse direction facilitates the separation of Rayleigh and Love waves. Though the narrow frequency spectrum of the surface waves prevents the inversion for depth‐dependent shear‐wave velocities, we are able to map the arrival times of the surface waves to laterally varying group and phase velocities for both Rayleigh and Love waves. Our results correlate well with the known geological structure. We outline a scheme for obtaining localized surface wave velocities from local noise sources and show how the processing of passive data benefits from a combination with well‐established exploration seismology methods. We highlight the differences with interferometry applied to crustal scale data and conclude with recommendations for similar deployments.  相似文献