Two-dimensional imaging of soil–bedrock interface by short-array beamforming technique     

《Soil Dynamics and Earthquake Engineering》2013

The depth to soil–bedrock interface, which is one of the major parameters in the site response analysis, has been often investigated by surface-wave tests. The round-robin tests for a surface-wave method in Korea revealed that a long measurement array in surface-wave tests is not appropriate in locating soil–bedrock interface. In this paper, for the improved profiling of depth to soil–bedrock interface in 2-D image, short measurement array was introduced for the beamforming technique, which is a robust array processing technique adopted in a long-array format for stiffness profiling. Numerical simulation and field applications of the short-array beamforming technique indicate that the method is valid even for surface wave propagation with mode-related complexity. Depth to soil–bedrock interface and shear-wave velocity profiles determined by the short-array beamforming technique were in good agreement with layer stratifications of boring logs, resistivity map, shear-wave velocity profiles of downhole tests and CAP-SASW tests.  相似文献   

地震台JCZ-1与JCZ-1T甚宽频带地震仪对比观测分析     

田文德  叶建庆  胡俊明 《地震研究》2013,36(3)

采用成都基准地震台JCZ-1型和JCZ-1T甚宽频带数字地震仪同一时间段记录的地方震、近震和远震的地脉动噪声做功率谱分析.结果表明,JCZ-1和JCZ-1T型甚宽频带地震仪在主要频带内对地噪声的响应程度是一致的.在高频端和低频端JCZ-1T型地震计分辨率更高,且信噪比更高,高出10 ～ 20 dB.JCZ-1型地震计由于长期使用导致材料老化以及受环境温度或气流微量变化的影响,地震计的噪声较高,可能对地震波记录的幅值产生5％左右的影响.JCZ-1T型地震计在安装过程中所采取的保温、防气流扰动等各种防护措施是可靠的.  相似文献   

地电井下观测装置技术指标的测试与认定讨论——井下观测设施构建与测试技术          下载免费PDF全文

马可兴  安海静  王康  张磊 《地震工程学报》2013,35(S1):143-147

观测技术系统的设施构建技术指标认定是观测技术的核心所在,本文结合地电井下观测设施构建工程^[1],着重讨论针对观测装置测试的需求、技术指标测试的方法以及认定的过程。文中以具体工程参数为例,给出4项测试结果,讨论了认定依据和认定过程,希望本讨论能对地电井下观测设施建设、指标的认定起到参考作用。  相似文献   

不同厚度层状边坡动力响应的模型试验研究          下载免费PDF全文

王丽丽  梁庆国  孙文  刘贵应 《地震工程学报》2013,35(3):590-596

采用振动台物理模拟试验方法,以4种不同覆土厚度的层状边坡模型为研究对象,水平输入振幅逐渐增大的正弦波加速度,分析了结构面上覆不同厚度土层对动力作用下边坡的稳定影响.研究了在动力作用下边坡的破坏位置和性质、破坏形式及最危险覆土厚度,验证了坡面放大效应与高程的关系,采用MIDAS/GTS软件对模型试验进行振型分析,分析了模型边坡的自振频率与覆土厚度的变化关系.试验结果表明：①模型破坏时最先出现的裂缝在边坡的中上部,且6 cm覆土厚度的模型对振动的响应最大,对应到实际工程中时12m厚度土层覆盖的边坡是最应该注意防护的.②不同厚度的土层破坏的形式不同：当土层厚度较薄时模型破坏较迅速,基本沿结构面发生整体滑动破坏,且滑动呈现一定的流体特性;当覆土较厚时裂缝先在模型中上部出现,随着振动的持续裂缝继续发展,最后发生整体性崩塌.③随着高程的增加峰值加速度总体呈放大趋势,但最大值出现在边坡中上部而非坡顶,说明不仅均质边坡有加速度的高程放大效应,层状边坡也具有加速度的高程放大效应.  相似文献   

不同结构性黄土的强度规律及传统强度准则适应性分析          下载免费PDF全文

陈昌禄  邵生俊  方娟  罗爱忠 《地震工程学报》2013,35(4):851-857

在真三轴试验基础上揭示了多种不同结构性原状黄土的强度变化规律,分析了在岩土工程实践中常用的Mohr-Coulomb准则和Matsuoka-Nakai准则对不同结构性原状黄土的适应性。结果表明:当结构性黄土的强度越大时,其在π平面上的破坏线越接近于抹圆曲边三角形,反之其在π平面上的破坏线越接近于抹圆角三角形;结构性黄土随着结构性的增大在π平面上的强度破坏线从抹圆角三角形逐渐向抹圆曲边三角形发展,最终趋近于Mises圆;两个强度准则所描述的强度都比结构性原状黄土的实际强度值小,Mohr-Coulomb准则的误差比Matsuoka-Nakai准则的误差大,并且随着结构性的增强其误差也逐渐增大。  相似文献   

首都圈地震活动完整性震级时空分布特征研究   总被引：1，自引：0，他引：1  

武敏捷  武安绪  龙锋  林向东  赵雯佳 《地震》2013,33(3)

根据首都圈活动构造展布特征,将首都圈划分为西区、中区、东区三个地区,采用拟合效果测试法计算首都圈及各分区1 970年以来最小完整性震级随时间的变化,并且依据各研究区域随时间的变化特征,将各研究区域从时间上划分为三个研究时段,分别研究各时段最小完整性震级的空间分布特征.研究表明,各时段的最小完整性震级在空间上具有明显的差异性,而且2000年以来各研究区域的最小完整性震级趋于稳定,MC均能控制在ML2.0以内.  相似文献   

Comparison of an Electrochemical and Luminescence‐Based Oxygen Measuring System for Use in the Biodegradability Testing According to Closed Bottle Test (OECD 301D)     

Judith Friedrich  Andreas Längin  Klaus Kümmerer 《洁净——土壤、空气、水》2013,41(3):251-257

The effects of persistent organic pollutants on the aquatic environment still can hardly be assessed. Therefore, ready biodegradability is a desired key characteristic of chemicals. Accordingly, biodegradation testing is of utmost importance and is a vital part within the risk assessment for organic chemicals. In the closed bottle test (CBT; OECD 301D) the degree of biological degradation of a chemical is assessed by monitoring the oxygen consumption so far with a Clark electrode as standard method. However, this method is time‐consuming, laborious and led to frequent fluctuations of the test results, which limited their validity. Due to these shortcomings, an optical system that enables contact‐free measuring of the oxygen concentration in a closed bottle, based on dynamic luminescence quenching, was examined. The test results were compared to those obtained with the “classical” electrochemical technique (Clark electrode). At first, a basic standard for the handling of the new instrument in the laboratory was developed. Then possible influencing factors, reliability, comparability, and reproducibility of the test results were investigated by running the CBTs in parallel with the electrode and optode method. The findings proved the new optode method to be unambiguously superior to the electrode technique. The frequency of fluctuations of the test results and time and effort necessary for the test run could considerably be reduced. The degradation kinetics of the test substances could be followed easily in the CBT by increasing the measuring points without much additional effort.  相似文献   

Polarimetric synthetic aperture radar change detection for specific land cover types     

《International Journal of Digital Earth》2013,6(4):334-344

This paper presents a supervised polarimetric synthetic aperture radar (PolSAR) change detection method applied to specific land cover types. For each pixel of a PolSAR image, its target scattering vector can be modeled as having a complex multivariate normal distribution. Based on this assumption, the joint distribution of two corresponding vectors in a pair of PolSAR images is derived. Then, a generalized likelihood ratio test statistic for the equality of two likelihood functions of such joint distribution is considered and a maximum likelihood distance measure for specific land cover types is presented. Subsequently, the Kittler and Illingworth minimum error threshold segmentation method is applied to extract the specific changed areas. Experiments on two repeat-pass Radarsat-2 fully polarimetric images of Suzhou, China, demonstrate that the proposed change detection method gives a good performance in determining the specific changed areas in PolSAR images, especially the areas that have changed to water.  相似文献   

基于统计检验法研究Amurian板块相对独立性   总被引：1，自引：0，他引：1       下载免费PDF全文

郭东美  许厚泽 《地球物理学报》2013,56(4):1246-1252

Amurian 板块是Zonenshain等提出的提出的东北亚地区内部一个构造亚板块.Amurian板块自提出以来就一直受到地学界的广泛重视.它到底是欧亚大陆的一部分,还是独立于欧亚大陆之外的一个独立次级构造块体?这个问题一直是是东亚,乃至欧亚大陆构造动力学研究的核心问题之一.许多学者从地质和地球物理学两个角度研究了Amurian板块存在的可能性.但是复杂的构造特征和稀少且弥散的地震分布使得Amurian问题充满了争议.全球卫星定位系统(GPS)技术的不断进步使得在短时间获得高精度、大范围、准实时的地壳运动观测数据,并确定地壳运动速度场成为可能.本文利用东北亚地区最新GPS资料,从大地测量学角度对东北亚地区的地壳运动特征进行分析,基于统计检验方法重点研究Amurian板块相对欧亚大陆的独立性及其边界等问题.  相似文献   

基于时间序列的InSAR相干性量级估计   总被引：3，自引：0，他引：3       下载免费PDF全文

蒋弥  丁晓利  李志伟  汪驰升  朱武  柯灵红 《地球物理学报》2013,56(3):799-811

本文提出了一种适用于InSAR数据处理的自适应相干性量级估计方法,该方法能够满足复信号随机平稳的假设前提,并兼顾运算效率与估计精度.此方法生成的相干图具有很好的分布特征,避免了影像空间分辨率的损失.提出的算法分为两个步骤:(1)根据地物后向散射特性,对时间序列SAR影像进行聚类分析,选择具有同分布的样本,保证SAR影像质地平稳条件;(2)对干涉图进行条纹频率估计,采用极大似然(ML)条纹频率估计方法去除系统相位引起的复信号非平稳性,并根据Cramer-Rao边界条件改善条纹频率的估计精度.以美国南加州洛杉矶地区的ENVISAT ASAR数据集为例,本文将新方法与现有方法进行了量化分析.结果表明,较传统方法而言,基于时间序列的相干性估计方法能够得到更可靠、精度更高、空间特征更鲜明的干涉相干图.  相似文献