排序方式： 共有44条查询结果，搜索用时 31 毫秒
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为了避免微动勘探技术中因忽略高阶模式瑞雷波而影响反演精度的不足,提出从微动面波中提取多模式瑞雷波频散曲线的映射式方法.该方法从微动信号入手,首先通过相关法提取多半径台阵的相关系数曲线,然后建立从多条相关系数曲线到多模式瑞雷波频散曲线的映射模型,最后采用分区拟合准则优化实现模型结构,达到提取微动面波中多模式瑞雷波频散曲线的目的.为验证方法的有效性,通过有限差分方法数值计算实际近表面应用中三种常见典型地质结构中的微动信号,采用映射式方法提取微动面波中多模式瑞雷波频散曲线,将提取结果和理论值进行对比分析.结果表明,映射式方法提取微动面波中多模式瑞雷波频散曲线可以满足反演地质结构的要求. 相似文献
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The aim of the paper is the definition of the material parameters of sediments in the western part of Thessaloniki useful in the prediction of strong ground motion. The region of interest is elongated in the E–W direction and is confined between the Kalochori suburb and the harbor of Thessaloniki, while in the N–S direction it is extended between the coastline and the region of sediments and outcrop rock boundary. Many geological and seismotectonic studies, as well as geophysical surveys with electrical soundings and geotechnical boreholes, contribute to our understanding of the general sedimentary structure. Nonetheless, these studies could not provide any information regarding the material stiffness in terms of shear wave velocity; the most useful parameter in site response studies. 相似文献
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长周期地脉动观测在西安地区地下构造调查中的应用 总被引：1，自引：0，他引：1
通过对西安两个区域(西安交通大学校园、市区东西与南北轴线)进行长周期地脉动观测、数据采集与分析,得到西安地区地下构造固有频率特性,进而推断出观测区地下软土层厚度分布趋势。经过对数据进行Nakamura法处理可以清晰看出:地基土层起着滤波器作用,有选择地滤掉某些成分,放大了某些频谱成分,使谱型局部受到改造;不同场地土质对地脉动的响应具有频率依赖性以及频率选择效应。同时探明观测区长周期地脉动的空间变化规律,了解了沉积层厚度以及横向变化规律,可为西安地区工程抗震提供参考依据。 相似文献
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Bodin et al. [Eng. Geol. 62 (2001) 159] reported three sets of maxima in observed H/V particle-motion spectra, where the longest-period set of peaks provided clear mapping information on the thickness of post-Cretaceous sediments in the Mississippi embayment, but the remaining peaks remained largely unexplained. A review of microtremor array studies for similar sites and similar frequencies suggests that the microtremor field is best interpreted in terms of Rayleigh-wave energy. Use of this approach, with modeling of particle-motion H/V ratios for realistic models of the Mississippi embayment, shows that the [Eng. Geol. 62 (2001) 159] second set of spectral maxima can be associated with higher-mode Rayleigh-wave energy, and may contain information on a possible velocity inversion in the shear-velocity profile of the site. A third spectral maximum appears to be associated with soft soils (loess) and may be able to be used for mapping the near-surface thickness (order 15 m) of this unit. 相似文献
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以福建省泉州市区和福州市区场地土的动力特性和地脉动频谱结构为研究对象,通过对这两个地区的地脉动信号的频谱分析获得频谱结构特征,由此来深入研究该地区岩土的动力特性及场地土层的地脉动动力响应。通过场地脉动的测试,利用快速傅立叶变换(FFT)方法对观测到的地脉动信号进行频谱分析。根据实际观测资料研究了地脉动频谱结构特征及场地土对地脉动的频率响应的特性。研究不同地基土层构造与地脉动的频率依赖以及频率选择作用。结果表明,地脉动的频谱特性与场地覆盖层厚度和地基土刚度的变化密切相关;覆盖层厚度是影响地脉动卓越周期的重要原因,其中软土层对地脉动的卓越周期有一定的放大作用。 相似文献
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We present the results of the analysis of array recorded microtremors at 14 sites, close to the edges of the Mygdonian basin in northern Greece (Euroseistest). These measurements were made in order to better constrain the geometry and velocity structure of the basin as the soil layers taper out close to rock outcrop, where geology is complex and we may expect significant changes of the subsoil structure over short distances. The data were analysed using the SPAC method and HVSR. The first interprets the measurements as Rayleigh waves (for the vertical component we analysed) and allows to invert a phase velocity dispersion curve from computed correlation coefficients. The second estimates a local transfer function directly, from ratios of Fourier amplitude spectra. A phase velocity dispersion curve could be derived for 12 of the 14 measurement sites, and at three of the sites no resonant frequency was observed in the HVSR. It is encouraging that we obtained good results at most of our sites, in spite of the lateral heterogeneity expected close to the edges of Euroseistest. Our results allow us to obtain shear wave velocity models at most of the measurement sites (12 out of 14). They are also useful to explore the relation between size of the array and wavelength range for which a dispersion curve may be estimated, which in our case has strong limitations. We identify the frequency of resonance of the sediments as a small loss of coherency in SPAC’s correlation coefficients. Finally, we also consider the applicability of the joint inversion of the resonance frequency determined using HVSR and the phase velocity dispersion curve obtained from SPAC. 相似文献
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Chun-Hsiang Kuo Ding-Shing Cheng Hung-Hao Hsieh Tao-Ming Chang Hsien-Jen Chiang Che-Min Lin Kuo-Liang Wen 《Soil Dynamics and Earthquake Engineering》2009
The Central Weather Bureau (CWB) and National Center for Research on Earthquake Engineering (NCREE) launched a project to build an engineering geological database for strong-motion stations in Taiwan in 2000. The project measures shear-wave velocity using the suspension PS-logging method. In this study, we conduct array measurements of microtremors and apply the stress wave propagation method (SWPM) at seven free-field strong-motion stations in Ilan County to estimate shallow shear-wave velocity structures. We focus on the sediment layers of the top 100 m to compare the shear-wave velocity structures of the three different methods. There are some misfits among the results of the three different methods; so we calculate the values of Vs30, Vs100 and plot S-wave travel-time curves of these methods for each site to analyze the misfits effectively. This analysis helped us to prove the efficiency of the microtremor array method in investigating shear-wave velocity structures in the shallow subsurface. Moreover, the horizontal-to-vertical ratios of microtremors for each survey point show the existence of divergence at the same site. We considered this as evidence that misfits are caused by the heterogeneous nature of sediments and also due to the nature of the methods as being one-, two- and three-dimensional. Furthermore, the average shear-wave velocity structure of microtremor arrays may be more representative of the whole site. 相似文献