共查询到20条相似文献，搜索用时 640 毫秒
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巴颜喀拉地块及其周边因地震动活动频繁成为中国地震预测研究的重要目标区,我们利用广义极值(GEV)分布对该地区的最大震级进行了极值统计分析.本文首先对于分布参数进行估计,然后计算出重现水平、地震平均复发周期与发震概率和震级危险率等参数,并比较了GEV分布99％分位数和b值截距法最大震级、历史最大震级.最后基于Monte Carlo模拟方法验证了运用GEV分布对研究区域做极值统计分析的稳定性.经计算,该地区6.0级地震的平均复发周期为1.8年,8.0级以上巨震的复发周期仅为76.8年.百年的重现水平高达8.08级.另外,该地块未来发生5.0～7.0级地震的概率较大,说明该地块未来仍然会比较活跃.Monte Carlo模拟结果表明,利用GEV分布探讨该地块的地震危险性在一定程度上是稳定的. 相似文献
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边坡稳定性的分析是边坡工程中最关键的,如何准确评价其稳定性是岩土工程界的热点问题。本文将Monte Carlo法应用于边坡稳定性的分析评价中,借助传统的极限平衡理论,建立边坡稳定的极限状态功能函数,并采用MATLAB语言编制Monte Carlo法计算边坡可靠度的计算机程序,从而获得边坡的失效概率与可靠度指标。相比传统的极限平衡理论,基于可靠度的分析方法能够更直观的反应边坡稳定性的现状,从而为工程人员提供更为可靠有效的帮助。 相似文献
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基于Zhou-Nowak数值积分法的结构整体概率抗震能力分析 总被引：2，自引：1，他引：1
结构整体概率抗震能力分析是新一代基于性能的地震工程中的一个重要模块,以往的研究主要采用平均值一次二阶矩法或Monte Carlo模拟法,分析了这2种方法存在的问题。为了有效地考虑结构系统随机性对结构整体抗震能力的影响,将Zhou-Nowak数值积分法与结构非线性静力推覆分析相结合,提出了基于Zhou-Nowak数值积分法的结构整体概率抗震能力分析方法,以新一代地震工程模拟仿真软件OpenSees为计算平台,以最大层间位移角作为结构整体抗震能力参数,对钢筋混凝土框架结构的整体概率抗震能力进行分析,并用Monte Carlo模拟法结果进行验证,从而建立了钢筋混凝土框架结构相应于不同性能水准的整体概率抗震能力模型。算例分析表明,所提方法是一种具有较高效率和较好精度的结构整体概率抗震能力分析方法。 相似文献
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在大震下 RC框架结构基于Pushover方法的失效相关性分析 总被引：3，自引：1，他引：2
目前,基于性能的建筑结构抗震设计成为世界各国土木工程界研究的热点之一.结构体系可靠度理论是进行结构性能分析的重要的理论基础.在结构体系可靠度的计算中,一个急待解决的问题是结构构件或截面间的失效相关性问题.本文基于pushover方法,采用Monte Carlo法和随机有限元法,在小震研究成果的基础上,进一步研究了钢筋混凝土框架结构在大震情况下的失效相关性问题,分别得出了框架梁、柱在大震作用下的部分失效相关性规律. 相似文献
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应用随机过程的正交展开方法,将地震动加速度过程展开为标准正交基函数与标准正交随机变量的线性组合形式。在此基础上采用随机函数的思想,将正交展开式中的标准正交随机变量表达为基本随机变量的函数形式,从而实现用一个基本随机变量来表达原地震动过程的目的。结合地震动过程的正交展开 随机函数模型与概率密度演化方法,对某大型渡槽结构进行随机地震反应分析与抗震可靠度计算;重点研究空槽和三槽有水等四种工况下渡槽结构控制点位移以及控制截面内力的随机地震反应与可靠度,进而获得渡槽结构控制点和控制截面的地震反应概率信息。 相似文献
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基于MVFOSM有限元可靠度方法的结构整体概率抗震能力分析 总被引：4，自引：2，他引：2
结构整体概率抗震能力分析既属于结构体系抗力统计分析研究内容,也属于地震易损性分析研究范畴,多采用数值模拟方法.作为一种不确定性传递的近似解析分析工具,平均值一次二阶矩方法(MVFOSM)广泛地应用于结构构件抗力的统计分析,但是很难应用于结构整体抗力的统计分析,主要困难在于结构反应是基本随机变量的隐式函数,梯度信息很难得到.将结构体系抗力的统计分析和地震易损性分析结合起来,通过基于MVFOSM的有限元可靠度方法,以新一代的地震工程模拟仿真软件OpenSees为计算平台,以最大层间位移角作为结构整体抗震能力参数,对钢筋混凝土框架结构的整体概率抗震能力进行分析,并用Monte Carlo模拟法结果进行验证,从而建立了钢筋混凝土框架结构的整体概率抗震能力模型.算例分析表明,MVFOSM有限元可靠度方法的精度和效率都很高,只需要进行一次有限元分析即可较为准确地获得结构整体概率抗震能力的前二阶矩信息. 相似文献
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《地震工程与工程振动》2015,(1)
基于阈值模型(POT)的广义帕累托分布(GPD)能充分利用样本中较大的观测值,在极值计算上有广泛的应用。本文讨论了广义Pareto分布以及该分布在风压极值计算中的应用。采用极大似然估计方法,对风压样本进行GPD拟合,得到具有一定保证率的风压极值。通过与峰值因子法(PFM)和经典极值方法(GEVD)计算的结果相比较,证明GPD拟合风压数据的效果较好,高保证率下的极值估计合理。对于高斯分布的风压样本,三种方法计算得到的结果比较接近;对于非高斯分布的样本,三种计算方法的结果存在较大差别,以GPD拟合的结果最优。应用GPD方法计算风压极值无需风压分布满足高斯假定,因而具有更广泛的适用性。 相似文献
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This paper presents a complete asymptotic analysis of a simple model for the evolution of the nocturnal temperature distribution on bare soil in calm clear conditions. The model is based on a simplified flux emissivity scheme that provides a nondiffusive local approximation for estimating longwave radiative cooling near ground. An examination of the various parameters involved shows that the ratio of the characteristic radiative to the diffusive timescale in the problem is of order 10−3, and can therefore be treated as a small parameter (μ). Certain other plausible approximations and linearization lead to a new equation whose asymptotic solution as μ → 0 can be written in closed form. Four regimes, consisting of a transient at nominal sunset, a radiative-diffusive boundary (‘Ramdas’) layer on ground, a boundary layer transient and a radiative outer solution, are identified. The asymptotic solution reproduces all the qualitative features of more exact numerical simulations, including the occurrence of a lifted temperature minimum and its evolution during night, ranging from continuing growth to relatively sudden collapse of the Ramdas layer. 相似文献
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Abstract We study the nonlinear asymptotic thin disc approximation to the mean field dynamo equations, as applicable to spiral galaxies. The circumstances in which sharp magnetic field structures (fronts) can propagate radially are investigated, and an expression for the speed of propagation derived. We find that the speed of an interior front is proportional to η//R ? (where η is the diffusivity and Rt the galactic radius), whereas an exterior front moves with speed of order , where γ is the local growth rate of the dynamo. Numerical simulations are presented, that agree well with our asymptotic results. Further, we perform numerical experiments using the 'no-z' approximation for thin disc dynamos, and show that the propagation of magnetic fronts in this approximation can also be understood in terms of our asymptotic results. 相似文献
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E. SZARANIEC 《Geophysical Prospecting》1980,28(2):257-268
The asymptotic approximation of Pekeris is replaced by two new procedures referred to as the two-point method and the multilayer method, other steps in the direct interpretation remaining unmodified. The new methods are based on the assumption that there are at least one or two consecutive sample points of the kernel curve containing the information on a particular layer and containing no information on the deeper layers. In any step, the identified covering layers are accumulated and the interpretation progresses to the successive deeper layer. The multilayer method is oriented towards interpretation of data severly contaminated by noise. The elimination of noise with simultaneous averaging of layer parameters is performed in the domain of Dar Zarrouk parameters. 相似文献
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V. V. Pak 《Izvestiya Physics of the Solid Earth》2007,43(9):783-790
A numerical compaction model of a fluid in a viscous skeleton is developed with regard for a phase transition. The temperatures of phases are different. The solution is found by the method of asymptotic expansion relative to the incompressible variant, which removes a number of computational problems related to the weak compressibility of the skeleton. For each approximation, the problem is solved by the finite element method. The process of 2-D compaction of a magmatic melt in the asthenosphere under a fault zone is examined for one-and two-temperature cases. The magmatic flow concentrates in this region due to a lower pore pressure. Higher temperature magma entering from lower levels causes a local heating of the skeleton and intense melting of its fusible component. In the two-temperature model, a magma concentration anomaly develops under the fault zone. The fundamental limitations substantially complicating the corresponding calculations within the framework of a one-temperature model are pointed out and the necessity of applying a multitemperature variant is substantiated. 相似文献
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《Journal of Applied Geophysics》1999,41(1):1-17
In the paper the principles of a new inversion method as well as the results of its application are described by using synthetic and field VES data. The basic idea of the method says that the horizontal changes in the layer thicknesses and the resistivities of the 2-D geological structure can be described by (expanding in series) functions of one variable. The coefficients of the functions are determined from the VES data by simultaneous inversion method using a least-squares technique. The local thicknesses and the resistivities of the geological structure are calculated from the coefficients from point to point along the profile. Using this method, the equivalence can considerably be reduced, and by using the functions chosen on the basis of a priori knowledge, the whole geological model can be determined by this inversion method. In the inversion the local 1-D forward modelling is used and this approximation is often applied in the VES practice. To qualify the results of the inversion, the correlation matrix for the coefficients are calculated and the error values for the local model parameters are introduced. 相似文献
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L. Fishman 《Pure and Applied Geophysics》2002,159(7-8):1637-1679
— Recently, de Hoop and coworkers developed an asymptotic, seismic inversion formula for application in complex environments supporting multi-pathed and multi-mode wave propagation (de Hoop et al., 1999; de Hoop and Brandsberg-Dahl, 2000; Stolk and de Hoop, 2000). This inversion is based on the Born/Kirchhoff approximation, and employs the global, uniform asymptotic extension of the geometrical method of “tracing rays” to account for caustic phenomena. While this approach has successfully inverted the multicomponent, ocean-bottom data from the Valhall field in Norway, accounting for severe focusing effects (de Hoop and Brandsberg-Dahl, 2000), it is not able to account properly for wave phenomena neglected in the “high-frequency” limit (i.e., diffraction effects) and strong scattering effects. To proceed further and incorporate wave effects in a nonlinear inversion scheme, the theory of directional wavefield decomposition and the construction of the generalized Bremmer coupling series are combined with the application of modern phase space and path (functional) integral methods to, ultimately, suggest an inversion algorithm which can be interpreted as a method of “tracing waves.” This paper is intended to provide the seismic community with an introduction to these approaches to direct and inverse wave propagation and scattering, intertwining some of the most recent new results with the basic outline of the theory, and culminating in an outline of the extended, asymptotic, seismic inversion algorithm. Modeling at the level of the fixed-frequency (elliptic), scalar Helmholtz equation, exact and uniform asymptotic constructions of the well-known, and fundamentally important, square-root Helmholtz operator (symbol) provide the most important results. 相似文献
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本文首先介绍了舒斯特（Schuster）以及别科娃（Benkova）日变分析的方法,并提出了利用“逐次近似法”分析日变经度效应的新方法;然后介绍了利用“逐次近似法”对中国地区1959年sq场分析的初步结果。结果表明,“逐次近似法”对于局部地区日变分析是适宜的。 相似文献
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Motivated by consideration of the solar tachocline, we derive, via an asymptotic procedure, a new set of equations incorporating velocity shear and magnetic buoyancy into the Boussinesq approximation. We demonstrate, by increasing the magnetic field scale height, how these equations are linked to the magneto-Boussinesq equations of Spiegel and Weiss (Magnetic buoyancy and the Boussinesq approximation. Geophys. Astrophys. Fluid Dyn. 1982, 22, 219–234). 相似文献
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Steven D. London 《地球物理与天体物理流体动力学》2014,108(3):323-332
We consider an electrically conducting rotating fluid governed by the shallow water magnetohydrodynamic equations with no diffusion. We use an a priori asymptotic technique (the method of geometric optics or ray method) to study weakly nonlinear hydromagnetic waves. These waves are intermediate in length in the following sense: they are much longer than the fluid depth but much shorter than the radius of the earth. The time scale for the waves is much longer than that of the free surface oscillations and the approximation varies on an even longer timescale. The waves we are considering are studied in the beta plane approximation for an ambient magnetic field parallel to the equator which varies in the direction perpendicular to the equator. The leading order approximation gives a dispersion relation for the waves, which are generally found to be confined to bands about the equator as well as in bands at higher and lower latitudes. At the next order of approximation, a conservation law is found for the wave amplitude. We also obtain an equation governing the behavior of the leading order mean azimuthal velocity which is forced to grow linearly with time. 相似文献