共查询到20条相似文献，搜索用时 31 毫秒
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Improvement of Nakamura technique by singular spectrum analysis 总被引：1，自引：1，他引：1
Roberto Carniel Fausto Barazza Paolo Pascolo 《Soil Dynamics and Earthquake Engineering》2006,26(1):55-63
In this work we investigate the application of the Singular Spectrum Analysis to improve Nakamura Technique. The SSA has a wide and multidisciplinary range of applications; it allows a time series to be decomposed into different components, e.g. the signal itself, as well as various noise components, which can be subsequently removed from the data. Removal of the minor component of the data can lead to significant improvements in the identification of the system. In this paper the use of SSA Technique allows to optimize the signal to noise ratio before computing the classical Nakamura spectral ratios. A number of typical applications are also presented. 相似文献
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用传统的经验转换函数方法评估场地效应需要有一个小孔径台阵,布设若干地震计,其中须有离软土台不远的基岩台。这种方法在天津市这样的大面积平原多震地区无法实现。天津市辖区面积11000km2,只有北部的蓟县是山区,市区是平原,南部的塘沽区、汉沽区、大港区是滨海第四纪巨厚沉积区。天津南部滨海区在1976年唐山MS7·8地震时受灾最重,死亡人员超过20000。天津是1949年以来我国唯一遭遇麦卡利地震烈度达到Ⅷ震灾的直辖市,也是此间我国遭遇地震最大(1976年宁河MS6·9)的城市。十五期间投巨资建立了数字地震观测台网,位于不同场地上的地震观测点清晰、完整地记录了若干有感地震。本文利用近场地面自由场地震三分向记录和Nakamura技术研究了天津地区的场地效应。并与唐山地震时天津地区实际遭受的宏观地震烈度相对比,结合天津地区的地下结构进行了分析。结果表明,Nakamura技术所获得的反映震害的指标(Nakamura技术的放大倍数)与实际震害基本一致。说明Nakamura技术在与天津地区地质构造类似的城市(平原、第四纪沉积层巨厚)如北京、上海、成都具有推广应用价值。我国正在建设大量自由场、数字化、宽频带、大动态地震观测点,该方法具有一定的应用前景。 相似文献
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论地脉动场地动力特性分析中的Nakamura方法 总被引：2，自引：0，他引：2
地脉动工程应用中的Ｎａｋａｍｕｒａ方法即用测点地脉动的水平分量与竖向分量谱比确定场地动力特性的方法,近年来成为工程场地动力特性分析中的研究热点。本文详细阐述了导出这一方法的试验依据和过程,并指出了其中存在的问题。 相似文献
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传统的评估场地效应的经验转换函数方法需要有一个小孔径台阵,布设若干地震计,其中须有离软土台不远的基岩台,但因北京市位于很大部分无基岩出露的大面积平原地区,所以无法实现.我们用Nakamura方法对北京地区进行场地效应评估.北京市"十五"期间建立了数字地震观测台网,位于不同场地上的强震观测点清晰完整地记录了若干有感地震.本文利用近场地面自由场强震三分向地震记录,通过Nakamura方法研究了北京地区的场地效应.并与1679年三河.平谷Ms8.1地震时北京地区实际遭受的宏观地震烈度相对比,结合北京地区的地下结构进行了分析.结果表明,用Nakamura方法所获得的反映震害的指标(Nakamura谱比率)有3个高值异常区,分别在北京东北部的怀柔县(值11.1、北京昌平区西部(值1O.1和市中心区(值8.1,这与三河.平谷Ms8.1地震时实际震害和观测点的地下局部构造基本一致.说明Nakamura方法在与北京地区地质构造类似的城市(平原、第四纪沉积层覆盖)如上海、成都、天津具有推广应用价值.我国正在建设大量自由场、数字化、宽频带、大动态强震观测点,该方法对于工程安全性评价具有一定的应用前景. 相似文献
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应用噪声谱比法, 收集了福建台网观测台站记录的地脉动噪声数据, 计算分析了85个观测台站的场地响应． 根据场地响应曲线形态将福建台网观测台站分为4类, 并简要分析了影响台站场地响应结果的因素． 计算结果表明, 福建台网观测台站台基情况普遍较好, 在台站观测频带内场地响应曲线平坦, 大部分台站均没有明显的频率放大点． 本文采用H/V谱比法与Moya方法所获得的37个台站的场地响应结果基本一致, 仅有少数台站存在较大差异． 应用场地响应分析结果, 结合计算震级时所量取的周期, 对福建台网观测台站的单台震级校正值进行了估计, 并与统计方法获得的单台震级校正值进行了比对． 结果表明, 两种方法获得的台站震级校正值存在一定的相关性, 但由于考虑的影响因素不同, 具体的台站震级校正值尚存在差别． 相似文献
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Hiroyuki Yamada Futoshi Nakamura Yasuharu Watanabe Marie Murakami Takeshi Nogami 《水文研究》2008,22(17):3545-3545
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L. J. TISON 《水文科学杂志》2013,58(1):5-8
Abstract A simple method is used to study the response of runoff in the Sahel to climate change. The statistical characteristics of rainfall are calculated over the western part of the Sahel for the period 1961–1990, using the BADOPLU network. Daily rainfall is simulated using a Markov process with Weibull distribution for rainfall depths. Runoff is modelled using a conceptual SCS model and the curve numbers are calculated for West Africa. Climate change is provided by simulations using the Arpège GCM (Scenario A1B), and a perturbation method is used on the parameters which describe the rainfall. Changes in rainfall are assumed to occur through increases in frequency, not intensity. Using Arpège, runoff is mainly found to increase, in depth and in number of events, by the end of the 21st century. Changes in evaporation and land use are not included in the analysis. The impact of this 21st century potential climate change (rainfall) on the runoff is found to be of the same magnitude as the impact of changes in land use. 相似文献
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Abstract In the Southwestern intermountain and high plains areas, precipitation is seasonal, with the major part of the rainfall occurring in the summer. Most winter precipitation occurs as low-intensity rain or snow along slow-moving cold fronts. Most summer precipitation occurs as short-duration, high-intensity thunderstorms from purely convective buildup or from convective cells developing along a weak fast-moving cold front. Almost all runoff occurs from the summer convective storms. Since runoff-producing precipitation is of primary interest at the Southwest Watershed Research Center, Agricultural Research Service, Tucson, Arizona, the convective storms have been most thoroughly analyzed. Duration, intensity, areal extent, movement, character, and return frequencies for varying volumes and intensities of these convective storms are analyzed from records from dense networks of recording rain gages in four study areas in Arizona and New Mexico. The primary study areas are the 58-square-mile Walnut Gulch Experimental Watershed at Tombstone, Arizona, and the 67-squaremile Alamogordo Creek Watershed near Santa Rosa, New Mexico. Three “record” storms of differing character occurring in 1960 and 1961 on Alamogordo Creek Watershed and one “record” storm in 1961 on the Wlanut Gulch Watershed are analyzed and compared in detail. 相似文献
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W. H. Ward 《水文科学杂志》2013,58(1):85-101
AbstractA new method is presented to generate stationary multi-site hydrological time series. The proposed method can handle flexible time-step length, and it can be applied to both continuous and intermittent input series. The algorithm is a departure from standard decomposition models and the Box-Jenkins approach. It relies instead on the recent advances in statistical science that deal with generation of correlated random variables with arbitrary statistical distribution functions. The proposed method has been tested on 11 historic weekly input series, of which the first seven contain flow data and the last four have precipitation data. The article contains an extensive review of the results.Editor D. KoutsoyiannisCitation Ilich, N., 2014. An effective three-step algorithm for multi-site generation of stochastic weekly hydrological time series. Hydrological Sciences Journal, 59 (1), 85–98. 相似文献
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SUMMARY Basing their studies on an extended Reynolds principle of similarity, the authors present in this paper a thorough theoretical investigation of the turbulent flow in pipes. Making appropriate assumptions regarding the distribution of the turbulent apparent viscosity over the entire pipe diameter, the well-known discharge formulas, i. e. the resistance laws, of Prandtl-V. Kármán for the hydraulically smooth and the hydraulically rough region, and of Colebrook for the transition region—the accuracy of these being well established by measurements—can be clearly shown to be correct. Thus it is also possible to determine the velocity distribution in the region near the wall for the hydraulically smooth region and the transition region, as well as for the hydraulically rough region. The concept, that the flow with a fully developed roughness effect begins when the laminar boundary layer at the wall disappears can be seen to be in close agreement with the asssumptions made. The limits which were established for the hydraulically rough region and the transition region correspond well with the curve plotted by PRANDTL and the boundary curve of Rouse. 相似文献
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