黄土高填方场地地震动参数特性分析   总被引：2，自引：0，他引：2       下载免费PDF全文

来春景  朱彦鹏  王春青  马天忠 《地震工程学报》2018,40(6):1168-1173,1223

削山造地后形成的黄土高填方场地对地震动参数特性影响较大。以实际工程项目为研究对象,构造不同填土高度的计算剖面,采用一维等效线性化方法计算土层地震动参数,分析基岩地震动输入参数和填土高度对场地地表放大效应的影响。研究表明:场地地震放大系数随填土层的高度增加呈递减趋势。在多遇地震动和基本地震动作用下,场地地震放大系数递减速度比罕遇地震动和极罕遇地震动作用下要大。当填土高度达到一定程度后放大效应趋于平稳;填土高度的变化,会改变地表加速度反应谱的形状。填土高度越大,地表反应谱长周期的频谱成分越显著,反应谱曲线向后移,反应谱峰值点均明显向长周期移动,并出现多个峰值点,反应谱特征周期值变大;下伏基岩的刚度越大,地表峰值加速度的放大效应越大。地表加速度反应谱特征值相比变小。当填土高度增大到一定程度时,下伏基岩的种类对地表地震动特性影响则不明显。该研究成果对高填方场地的地震安全评价和结构抗震设计提供参考。  相似文献   

设计反应谱标定方法的研究现状与讨论          下载免费PDF全文

蒋晓涵  薄景山    王竞  韩昕  郭晓云  赵培培  谭启迪 《世界地震工程》2018,34(4):038-48

设计反应谱及其标定方法的研究是工程抗震研究领域的基本问题之一。在现有研究成果的基础上，归纳和总结了设计反应谱及其标定方法的研究历史和现状；评述了研究进程中的若干节点问题；介绍了设计反应谱的标定原理和当前几种有代表性的设计反应谱的标定方法；分析了设计反应谱标定参数的影响因素。在此基础上，对设计反应谱及其标定方法研究中的强震资料积累问题、谱形状问题、标定参数的确定问题以及标定方法等问题进行了讨论并提出了改进和进一步研究的建议。  相似文献   

相关和频谱分析法在岩溶系统中的应用研究综述     

李建鸿  蒲俊兵  张陶  王赛男 《中国岩溶》2020,39(3):335-344

岩溶含水层由多重含水介质组成，具有高度的非均质性，从系统角度出发，将岩溶系统看作是一个过滤器，将降雨作为输入信号，泉流量、水位、电导率、浊度等物理化学参数作为输出量进行相关和频谱分析是认识岩溶系统内部结构特征的有效方法。文章综述了相关和频谱分析法在岩溶系统研究中的应用，首先介绍了相关和频谱分析法基本理论的形成、发展过程和研究意义，然后总结了如何根据不同的研究目的选择相关和频谱分析法使用的时间序列的长度、周期和类型，最后阐述了该方法应用于岩溶系统分析的局限性。   相似文献   

Separation of PP- and PS-wave reflected seismic data using two-dimensional finite offset common-reflection-surface traveltime approximation     

Raphael Di Carlo Silva dos Santos  João Carlos Ribeiro Cruz  Manuel de Jesus dos Santos Costa 《Geophysical Prospecting》2020,68(7):2046-2063

Recently, the interest in PS-converted waves has increased for several applications, such as sub-basalt layer imaging, impedance estimates and amplitude-versus-offset analysis. In this study, we consider the problem of separation of PP- and PS-waves from pre-stacked multicomponent seismic data in two-dimensional isotropic medium. We aim to demonstrate that the finite-offset common-reflection-surface traveltime approximation is a good alternative for separating PP- and PS-converted waves in common-offset and common shot configurations by considering a two-dimensional isotropic medium. The five parameters of the finite-offset common-reflection-surface are firstly estimated through the inversion methodology called very fast simulated annealing, which estimates all parameters simultaneously. Next, the emergence angle, one of the inverted parameters, is used to build an analytical separation function of PP and PS reflection separation based on the wave polarization equations. Once the PP- and PS-converted waves were separated, the sections are stacked to increase the signal-to-noise ratio using the special curves derived from finite-offset common-reflection-surface approximation. We applied this methodology to a synthetic dataset from simple-layered to complex-structured media. The numerical results showed that the inverted parameters of the finite offset common-reflection-surface and the separation function yield good results for separating PP- and PS-converted waves in noisy common-offset and common shot gathers.  相似文献   

STUDY ON FOCAL DEPTH OF THE M_S5.4 CANGWU EARTHQUAKE IN GUANGXI          下载免费PDF全文

ZHAO Tao  CHU Ri-sheng  NI Si-dao  WANG Ying  ZHOU Yong  ZENG Xiang-fang 《地震地质》2019,41(3):619-632

On July 31th, 2016, a magnitude 5.4 earthquake struck Cangwu Country, Guangxi Zhuang Autonomous Region, it was the largest earthquake recorded by Guangxi Seismological Network since it set up. The number of people affected by the earthquake had reached 20 000, and the direct economic losses caused by the earthquake were nearly 100 million Yuan. After the earthquake, USGS provided a global earthquake catalog showing that the focal depth of Cangwu earthquake was about 24.5km. However, the result given by the Global Centroid Moment Tensor showed the focal depth of this earthquake was 15.6km. However, the result obtained by Xu Xiaofeng et al. using CAP method was 5.1km. It was clear that the focal depths of Cangwu earthquake given by different institutions were quite different from each other. However, accurate focal depth of the earthquake has important significance for exploring the tectonic mechanism near the epicenter, so it is necessary to further determine the more accurate depth of the Cangwu earthquake. In order to further accurately determine the focal depth of Cangwu earthquake, we used the global search method for travel-time residual to calculate the focal depth of this earthquake and its error range, based on the regional velocity model, which is a one-dimensional velocity model of the Xianggui tectonic belt produced by the comprehensive geophysical profile. Then, we inverted the focal mechanism of this earthquake with the CAP method. Based on this, the focal depth of Cangwu M_S5.4 earthquake was further determined by the method of the Rayleigh surface wave amplitude spectrum and the sPL phase, respectively. Computed results reveal that the focal depth of this earthquake and its error range from the travel-time residual global search method is about(13±3)km, the focal depth inverted by CAP method is about 10km, the focal depth from sPL phase is about 10km, and the focal depth from Rayleigh surface wave amplitude spectrum is about 9~10km. Finally, we confirmed that the focal depth of Cangwu M_S5.4 earthquake is about 10km, which indicates that this earthquake still occurred in the upper crust. In the case of low network density, the sPL phase and Rayleigh wave amplitude spectrum recorded by only 1 or 2 broadband stations could be used to obtain more accurate focal depth. The focal depth's accuracy of Cangwu M_S5.4 earthquake in the USGS global earthquake catalog has yet to be improved. In the future, we should consider the error of the source parameters when using the USGS global earthquake catalog for other related research.  相似文献   

回填土不确定性对场地地震反应的影响          下载免费PDF全文

张海  陈贺  尤红兵  李克强 《地震工程学报》2019,41(2):370-377

选取某核电场地控制性钻孔的厚度、剪切波速、密度等实际勘探数据,通过改变回填土剪切波速,分析了回填土不确定性对场地地震动参数的影响。研究结果表明:在回填土层厚度不变和模型总厚度不变的情况下,地表的水平向峰值加速度随着回填土剪切波速的增大而减小,但水平向峰值加速度增幅逐渐减小;回填土剪切波速到达一定的波速就不再影响地表水平峰值加速度;随着回填土剪切波速的增加,整个反应谱的谱值都普遍减小。  相似文献   

2012年唐山4.8级地震强震动记录特征及场地相关特性分析     

齐玉妍  孙丽娜  吕国军  李慧 《地震》2019,39(4):172-180

2012年5月28日河北省唐山市古冶区与滦县交界发生4.8级地震, 国家强震动台网中心在河北、 天津和北京的94个强震动台站记录到了本次地震的加速度。 本文给出了获取记录的强震动台站分布及强震动记录结果, 统计了强震动记录数量随震中距的变化, 给出了3个较小震中距台站记录到的加速度时程; 绘制了空间地震动峰值加速度等值线图及周期0.2 s、 2.0 s加速度反应谱值的等值线, 发现峰值加速度等值线与长周期加速度反应谱等值线极值分布具有明显地域差异, 分析认为是由于厚沉积层对长周期地震动具有放大作用造成的。 通过强震动记录与适用于本区的三个衰减关系对比, 分析了此次地震的峰值加速度衰减特征, 同时研究了周期0.2 s、 2.0 s加速度反应谱值的衰减特征, 周期2.0 s反应谱值随震中距的衰减与衰减关系能较好地对应, 然而在震中距100～130 km沉积层较厚的集中地区, 表现出了实际记录较衰减关系值偏大的现象, 认为同样是由于厚沉积层对地震动加速度反应谱长周期的放大作用导致的。 研究了震中距差别不大的情况下, 场地类型与沉积层厚度对反应谱特征周期的影响, 对比基岩台站与软弱地基土层台站的强震动记录反应谱, 发现软弱土层台站的土层对地震动有一定的放大作用, 导致中长周期地震动被放大, 对比位于沉积层较薄的隆起区台站与位于沉积层较厚的凹陷区台站强震动记录反应谱, 发现厚的沉积层不仅对反应谱长周期有放大的作用, 同时也会使得反应谱特征周期值变大。  相似文献   

山西定襄七岩泉新旧测氡仪水氡测值稳定性及映震分析     

刘俊芳  郭宝仁  郭宇  高文玉  刘金柱 《地震地磁观测与研究》2019,40(2):115-122

2014年山西定襄七岩泉新增BHC-336智能定标器,对新、旧2套测氡仪的水氡测值,就稳定性、数据一致性、内在质量等进行对比分析,结果显示,因存在系统误差,2台测氡仪水氡测值稳定性均值存在差异,测量精度和性能具有一致性;与新测氡仪相比,旧测氡仪水氡测值相对偏差和均值标准误差更小,精度更高,数据相关程度较高,数据稳定性更好。定襄水氡对华北5级以上地震具有较好的映震能力,新测氡仪对2016年4月7日原平4.6级地震映震效能比旧测氡仪灵敏。  相似文献   

Removal of water‐surface reflection effects with a temporal minimum filter for UAV‐based shallow‐water photogrammetry          下载免费PDF全文

I GD Yudha Partama  Ariyo Kanno  Motoyasu Ueda  Yoshihisa Akamatsu  Ryutei Inui  Masahiko Sekine  Koichi Yamamoto  Tsuyoshi Imai  Takaya Higuchi 《地球表面变化过程与地形》2018,43(12):2673-2682

The recent development of structure‐from‐motion (SfM) and multi‐view stereo (MVS) photogrammetry techniques has enabled semi‐automatic high‐resolution bathymetry using aerial images taken by consumer‐grade digital cameras mounted on unmanned aerial vehicles (UAVs). However, the applicability of these techniques is sometimes limited by sun and sky reflections at the water surface, which render the point‐cloud density and accuracy insufficient. In this research, we present a new imaging technique to suppress the effect of these water‐surface reflections. In this technique, we order a drone to take a short video instead of a still picture at each waypoint. We then apply a temporal minimum filter to the video. This filter extracts the smallest RGB values in all the video frames for each pixel, and composes an image with greatly reduced reflection effects. To assess the performance of this technique, we applied it at three small shallow‐water sites. Specifically, we evaluated the effect of the technique on the point cloud density and the accuracy and precision of the photogrammetry. The results showed that the proposed technique achieved a far denser point cloud than the case in which a randomly chosen frame was used for each waypoint, and also showed better overall accuracy and precision in estimating water‐bottom elevation. The effectiveness of this new technique should depend on the surface wave state and sky radiance distribution, and this dependence, as well as the applicability to large areas, should be investigated in future research. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

长江三角洲蓝图重绘的基础科学问题:进展与未来研究     

汪亚平  贾建军  杨阳  周亮  冯威  高建华  魏稳  李占海  史本伟  高抒 《海洋科学》2019,43(10):2-12

在全球气候变化和人类活动影响加剧的背景下,作为河口海岸重要子系统的三角洲正在发生快速变化。长江三角洲地处长江入东海交汇处,是中国最重要的经济核心区之一,对邻近区域乃至整个长江经济带经济社会发展都起着重要作用。由于全球变暖、海面上升和强烈人类活动引发了三角洲系统状态转换,因此以往基于恒定系统状态而获得的有关长江三角洲的认识已不能满足未来需求,迫切需要对未来海面变化、极端事件、流域与河口工程影响下的三角洲物质循环条件、物理过程、地貌冲淤演化、源-汇格局调整等科学问题进行深入研究。在三角洲系统行为、未来演化趋势的预测能力建设中,应重视从海面到海底的综合立体观测系统的发展,以获取关键数据;基于三角洲系统的时、空演化特征,建立三角洲本征态和衍生态的谱系理论。未来需针对系统状态转换而调整原先的经济社会发展模式,以便保护自然资源、重建生态系统,更好地支撑长江经济带发展,重绘长江三角洲发展蓝图。  相似文献