The importance of crustal structure in explaining the observed uncertainties in ground motion estimation     

John Douglas  Hideo Aochi  Peter Suhadolc  Giovanni Costa 《Bulletin of Earthquake Engineering》2007,5(1):17-26

In this short article, the possible reduction in the standard deviation of empirical ground motion estimation equations through the modelling of the effect of crustal structure is assessed through the use of ground-motion simulations. Simulations are computed for different source-to-site distances, focal depths, focal mechanisms and for crustal models of the Pyrenees, the western Alps and the upper Rhine Graben. Through the method of equivalent hypocentral distance introduced by Douglas et al. [(2004) Bull Earthquake Eng 2(1): 75–99] to model the effect of crustal structure in empirical equations, the scatter associated with such equations derived using these simulated data could be reduced to zero if real-to-equivalent hypocentral distance mapping functions were derived for every combination of mechanism, depth and crustal structure present in the simulated dataset. This is, obviously, impractical. The relative importance of each parameter in affecting the decay of ground motions is assessed here. It is found that variation in focal depth is generally more important than the effect of crustal structure when deriving the real-to-equivalent hypocentral distance mapping functions. In addition, mechanism and magnitude do not have an important impact on the decay rate.  相似文献   

倒虹吸混凝土管道的地震反应分析          下载免费PDF全文

徐平  唐献富  夏唐代 《地震工程学报》2007,29(4):352-356

基于土体的等效粘弹性模型,结合场地典型剖面的土体特性以及室内实验确定的各力学参数,采用时域积分和迭代的方法研究了沁河倒虹吸管道在地震作用下的反应,分析了管道截面中间底部点绝对地震位移、顶部点相对于底部点的地震动位移及管道动静综合主应力的变化规律;并根据有限元时程法的分析结果,按照混凝土承载能力极限状态设计式,对管身混凝土的抗拉、抗压安全度进行校核。结果表明,在人工地震波、调整后的E1 Centro和Pulgas地震波分别输入的情况下沁河渠道倒虹吸管道均满足抗震要求。  相似文献   

位场延拓的积分-迭代法   总被引：22，自引：14，他引：22       下载免费PDF全文

徐世浙 《地球物理学报》2006,49(4):1176-1182

本文介绍一种新的位场延拓方法——积分-迭代法.将起伏面上的实测位场值，垂直投影至起伏面下部的一个水平面上，作为该水平面上的位场初始值.根据该水平面上的初始值，用积分方法计算起伏面上的位场值.用起伏面上的实测值与计算值的差值，对水平面上的位场值进行校正.如此反复迭代，直至起伏面上的实测值与计算值的差值小到可以忽略.有了水平面上的位场值后，就可以用积分的方法或其他方法计算水平面以上的任意曲面或水平面的位场值.该方法原理简单，不用解线性代数方程组，有较高的计算速度.它特别适用于位场向下延拓，有良好的延拓效果.本文还介绍了积分迭代法的应用实例.  相似文献   

常速叠加－DMO－叠后偏移等效叠前偏移          下载免费PDF全文

王振华 《地球物理学报》1994,37(6):795-803

常速叠加是根据给定的速度将炮检距空间的地震数据映射到叠加速度空间，在实际叠加速度位置形成叠加能量；速度变换是将叠加速度空间的能量数据映射到均方根速度空间，消除地层倾角对速度的影响，这实际上是一种ＤＭＯ方法；常速偏移是在每个均方根速度剖面上独立地进行波场归位，消除反射点位置对速度的影响．经过这三步处理获得最终叠前偏移结果．  相似文献   

大气的垂直结构与遥相关型          下载免费PDF全文

杨成彬  王梅华  彭茹 《应用气象学报》1993,4(4):492-497

利用球面上20°N以北和20°S以南的500hPa高度场资料研究了大气的垂直结构与遥相关型的关系。结果表明，正压扰动与波列结构的遥相关型一致，而斜压扰动则与带状结构遥相关型一致。  相似文献   

裂隙参数对衰减各向异性影响的数值模拟     

蔡晓刚 《中国地震研究》2012,26(1):97-109

Propagation through stress-aligned fluid-filled cracks and other inclusions have been claimed to be the cause of azimuthal anisotropy observed in the crust and upper mantle.This paper examines the behavior of seismic waves attenuation caused by the internal structure of rock mass,and in particular,the internal geometry of the distribution of fluid-filled openings Systematic research on the effect of crack parameters,such as crack density,crack aspect ratio(the ratio of crack thickness to crack diameter),pore fluid properties(particularly pore fluid velocity),VP/VS ratio of the matrix material and seismic wave frequency on attenuation anisotropy has been conducted based on Hudson’s crack theory.The result shows that the crack density,aspect ratio,material filler,seismic wave frequency,and P-wave and shear wave velocity in the background of rock mass,and especially frequency has great effect on attenuation curves.Numerical research can help us know the effect of crack parameters and is a good supplement for laboratory modeling.However,attenuation is less well understood because of the great sensitivity of attenuation to details of the internal geometry.Some small changes in the characteristics of pore fluid viscosity,pore fluids containing gas and liquid phases and pore fluids containing clay can each alter attenuation coefficients by orders of magnitude.Some parameters controlling attenuation are therefore necessary to make reasonable estimations,and anisotropic attenuation is worth studying further.  相似文献   

Investigation on the accuracy of the N2 method and the equivalent linearization procedure for different hysteretic models     

《Soil Dynamics and Earthquake Engineering》2016

In this paper, an extensive parametric study was carried out to evaluate the dynamic response of single degree of freedom (SDOF) systems with elasto-plastic and flag-shape hysteretic behaviour for three different dissipation capacities. Three sets of natural accelerograms were used, each one composed by at least 7 records which are on average spectrum-consistent in pseudo-acceleration, spectral displacement or both of them. All sets were also employed to draw the inelastic spectra for different ductility values. Such rigorous spectra were then compared with the approximated curves calculated using the N2 method and the Equivalent Linearization Procedure (ELP) based on the use of overdamped elastic spectra.The analyses demonstrate a general accuracy of the N2 method, which is mostly based on the ductility of the system, even for the hysteretic behaviour characterised by reduced energy dissipation. Larger discrepancies were found for systems with lower damping ratios and reduced fundamental periods. The ELP, which mainly depends upon the dissipated energy, led instead to overall slightly larger discrepancies than the N2 method, particularly for not dissipative and ductile systems, whereas the approximation is generally acceptable for elasto-plastic systems.  相似文献   

Evaluation of cyclic shear strength of mixtures with sand and different types of fines     

Uk-Gie Kim  Li Zhuang  Dongwook Kim 《Marine Georesources & Geotechnology》2017,35(4):447-455

Soils are classified as sandy soils and clayey soils in most soil classification systems, and appropriate equations are used for practical design, depending on soil type, to represent each soil behavior. Sand-clay mixtures, however, need a special standard to evaluate their specific behaviors since they are categorized as intermediate soils or transitional soils and typically show intermediate properties. In this article, a series of cyclic triaxial tests were conducted on specific sand-fines mixtures with three fine types and various fine contents. The behaviors of various soil mixtures (silica sand with Iwakuni natural clay, Tottori silt, and Kaolin clay) were investigated by considering a concept of granular void ratio expressed in terms of sand structure. The cyclic shear strengths of the soil mixtures were also evaluated by increasing the fine content but no more than the threshold fine content. In the results, the cyclic deviator stress ratio decreased in dense soils whereas it increased in loose soils by increasing the fine content. In addition, a simple equation was proposed to predict the liquefaction resistance of sandy soils by evaluating the cyclic deviator stress ratio with a concept of equivalent granular void ratio.  相似文献   

中尺度地形背风波的作用及其应用   总被引：16，自引：3，他引：13  

朱民  余志豪  陆汉城 《气象学报》1999,57(6):705-714

文中探讨了中尺度地形背风驻波及对天气系统发生发展的影响问题,通过建立一个含类似大别山地形作用的简化数学模型并进行了数值计算,结果表明,当过山气流u取１０１ｍ／ｓ量级,层结参数Ｎ取１０(－３)ｓ(－１)量级,其比值Ｕ／Ｎ约为３×１０３～４×１０３时可出现一种相当正压的地形背风波,其波长近于Ｕ／ｆ～１０２ｋｍ（ｆ为柯氏参数）。结合上述理论结果和实际暴雨个例,分析指出在江淮梅雨期间,当有移动性的暴雨区移至大别山定常背风波的适当位置时,暴雨会得到增幅。  相似文献   

Optimal damper placement for building structures including surface ground amplification   总被引：2，自引：0，他引：2  

Izuru Takewaki  Koji Uetani 《Soil Dynamics and Earthquake Engineering》1999,18(5):307

A systematic method for optimal added damper placement in building structures is developed, taking into account the response amplification due to the surface ground. Non-linear amplification of the surface ground is described by an equivalent linear model. Hysteretic damping of the surface ground and radiational damping into the semi-infinite visco-elastic ground are included in the model. An original steepest direction search algorithm is applied to the interaction model. Closed-form expressions of the inverse of the coefficient matrix (tri-diagonal matrix) enable one to compute the transfer function and its derivative with respect to design variables very efficiently. It is shown that the ratio of the fundamental natural period of the structure to that of the surface ground is a key parameter for characterizing the optimal damper placement. Several examples for different soil conditions are presented to demonstrate the effectiveness and validity of the present method.  相似文献