共查询到20条相似文献，搜索用时 218 毫秒
1.
本文从一阶方程组形式的波动方程出发,发展了一种计算二维不均匀介质中点源P-SV波响应的近似方法。该方法通过引入线分布的应力作为震源,利用二维有限差分方法计算出线源响应,然后再经过波形校正和几何扩散校正得出相应的近似点源响应。通过把波形和振幅与精确解比较表明,该方法具有较好的精度。由于有限差分方法对于介质中速度和密度的分布没有特殊要求,另一方面,本文所给出的震源可以适用于位错点源、爆炸源或集中力源,因此上述方法十分适合于研究横向不均匀介质中的近场强地运动、爆炸振动或地震勘探等问题。 相似文献
2.
3.
4.
考虑震源破裂过程的三维地震动数值模拟一般需将震源包含在计算区域中,这样的计算模型区域大,计算量大,尤其是对于断层埋深较大的情况。本文对破裂断层下地壳分层结构引起的反射波的影响进行了分析,分别对改变断层下方介质的密度和波速两个参数的模拟结果进行了对比,结果表明:断层下方地壳分层结构引起的反射波对地表观察点地震动时程的影响很小,可以忽略。因此进行三维地震动数值模拟可以不考虑断层下介质的影响,从而可以大大减小计算区域,提高计算效率。 相似文献
5.
为估计二维横向不均匀，非弹性介质的地面运动，将振型叠加法和有限差分方法相结合，发展一种复合技术，无论震源距大小，都可以计算地震形成的局部波场，它可考虑震源、路径和局部场地土的影响。 相似文献
6.
基岩地震动的一个相干函数模型--倾滑断层情形 总被引：6，自引：0，他引：6
本文研究了基岩随机地震动的空间变化规律，考虑了震源破裂速度、子源个数、震源深度和介质传播速度等因素的影响。对应于每个样本，用数值模拟方法计算了采用震源位错模型的弹性半空间近场地震动场，最后通过统计方法给出了一个倾滑断层情形下的近场基岩地震动的相干函数模型。这一方法可以补充常用的统计方法因观测资料有限而导致的欠缺。 相似文献
7.
8.
本文提出一种结合广义射线和有限差分理论而形成的混合方法（以下简称混合方法）．在介质均匀区（包括平行介质分层区）应用广义射线理论，在介质不均匀区应用有限差分理论．在这种结合过程中，把均匀区广义射线的结果作为不均匀区有限差分区波场连续的输入．对于均匀介质模型，混合方法理论地震图和广义射线理论地震图、广义反射透射系数矩阵及离散波数法地震图的对比，取得了满意的结果，在数值上证明了该方法的正确性．计算了１９９０年８月５日Ｈａｋｏｎｅ地震前震在日本Ａｓｈｉｇａｒａ山谷盲测点的响应，理论地震图和实际资料的比较同样取得好的结果．这种方法可用于地震勘探、工程地震、强地面运动的研究． 相似文献
9.
10.
基于曲线网格有限差分方法研究了地震波在不同坡度的山体地形及水平地表模型中的传播,得到了各模型速度波形及地表峰值速度特征,从地形自身特征及震源特征两方面出发讨论了地形效应:一是相同的震源模型下地形坡度、形状对地震动的影响;二是同一山体模型下地震动对不同震源机制的点源以及相对复杂的有限断层的响应.主要结论如下:(1)一般情况下,地形放大效应在坡度较大的地方比较明显,并随着坡度的增加而增大,但在某些特定情况下,放大效应与坡度并不满足正相关,且这种情况的发生与震源性质无关,可能仅受地形形态自身的影响;(2)对于不同的震源机制,地面运动各分量受地形影响程度不同,总体上水平分量受地形影响程度更大;(3)震源机制和震源激发的波的频率会影响放大效应最大值出现的位置,放大效应最大值不一定出现在山顶处,有可能会出现在起伏地形的震源对侧,出现位置可能与波的相互作用有关;(4)有限断层模型下,地面运动特征相对更为复杂,地形效应不仅受断层模型几何特征的影响,同时断层破裂过程对其也有着重要的影响. 相似文献
11.
本在震源为双侧线状断层破裂模型的假定下，根据震源理论和波谱随空间坐标的展开式，得到了场地两点地震动Fourier谱的表达式Ab(f)=Aa(f)exp(a1δ0 a2δθ，中提出了将双侧破裂模型分解为两个单侧破裂模型计算双侧破裂模型a1和a2的数值方法，以一次地震（M＝6）为例，分析了双侧破裂模型对地震动空间相关性的影响，计算了 a1和a2的实部和虚部以及孔径随震中距，方位角和频率变化的三维图像。 相似文献
12.
This paper presents the application of the finite element method for analysing the two-dimensional response of reservoir-dam systems subjected to horizontal ground motion. The interaction between the dam and the reservoir as well as the compressibility of water has been taken into account. The complete system has been considered to be composed of two substructures, namely the reservoir and the dam. To take into account the large extent of the reservoir, it has been idealized using specially developed infinite elements coupled with standard finite elements while the dam is represented using finite elements alone. Structural damping of the dam and radiation damping in the fluid phase have been accounted for in the analysis. It is concluded that the effect of radiation damping is considerable at high frequencies of excitation. The coupled response of the system is significantly large at and near the fundamental natural frequency of the system in comparison to the uncoupled responses. The method is computationally quite economical, capable of taking into account the arbitrary geometry of the system and is recommended for practical application. Further applications and extensions of the approach to three dimensional analyses are possible. 相似文献
13.
On the basis of previous study of the 1679 Sanhe-Pinggu(M8.0) earthquake,the biggest event in history ever recorded in Beijing and its adjacent area,we made a 3-D strong ground motion simulation utilizing the staggered-grid finite differences method to study the distributions of peak ground velocity with different earthquake source models in the Beijing region.In the paper,earthquake source models and a transmission medium velocity model are established and the corresponding parameters are given in accordance to the results from a related previous study.Then,using a three-dimensional finite difference computing program of near-fault strong ground motion developed by Graves,the peak ground velocity caused by a destructive earthquake in the Beijing area is simulated.In our computation model,the earthquake source is 3km in depth,and a total number of 21,679 observation points on the ground surface are figured out.The transmission medium velocity model is composed of four stratums which are the Quaternary deposit,the upper crust,the upper part of the middle crust and the lower part of the middle crust.With the minimum grid spacing of 0.15km,a total of 2.28×106 grids are generated.Using a time step of 0.02 seconds we calculated the peak ground velocity for a duration of 8 seconds.After the analysis of the simulation results,we observed some basic characteristics of near-fault strong ground motion such as the concentration effect of near-fault peak ground velocity,rupture directivity effect,hanging wall effect,and basin effect.The results from our simulation and analysis suggest that the source and transmitting medium parameters in our model are suitable and the finite difference method is applicable to estimate the distribution of strong ground motion in the study region. 相似文献
14.
In this study, a three dimensional finite element (FE) model of the Vincent Thomas bridge is developed using a widely used software. In order to show the appropriateness of the model, the eigenproperties of the bridge model are evaluated and compared with the results of system identification from ambient vibration and the 2008 Chino Hills earthquake response data. A new simulation technique is developed to generate spectrum-compatible spatial variable ground motions. The response of Vincent Thomas bridge under spatially varying ground motion is evaluated by nonlinear time history analysis. Using spatially variable motions, it is found out that the response in some locations on the bridge girder, may be under-predicted even if the motion with maximum intensity is uniformly applied at all supports. 相似文献
15.
本文首先将一般剪切位错点源表示成四种基本点位错的组合,断层面倾角和滑动系数仅与组合系数有关.利用将三维动力学问题化为两维的处理方法,将每一基本点源问题化成求解位移函数的轴对称问题,最后将人工透射边界的处理方法同有限差分结合起来,提出一种简便、节省的计算理论地震图的方法.利用这种方法获得了四种基本点位错源的典型近场理论地震图,并初步讨论了近场地面运动的若干特征,表明浅源地震近场地面位移中震相不能分离,且点位错源在近场产生大小相当的水平与垂直位移.本文的方法可用于研究复杂的近场地震波传播问题. 相似文献
16.
2013年4月20日在我国四川省发生了芦山MS7.0地震,地震给当地群众的生命财产安全带来了巨大的损失,其中最严重的破坏发生在震中附近的芦山、宝兴等地区.根据地震发生的快速反演结果,及发震断层面上滑动位移的分布情况,构建有限断层模型,对近断层区域的强地面运动进行初步计算,并基于强地面运动的模拟结果给出震区烈度分布的初步估计.模拟结果显示：模拟烈度图显示极震区的烈度在IX级左右,VI级烈度影响范围大致为16000 km2,该结果与中国地震局于4月27日给出的震区实测烈度图一致程度较高.强烈地震发生后,基于近断层强地面运动模拟计算的结果,可以给出相对合理的地震烈度分布情况估计,对震区震情判定及救灾工作具备较高的现实意义. 相似文献
17.
首先基于地震作用下地下结构的变形受周围地基土变形控制这一相互作用特征,在反应位移法的基础上讨论两种简化分析方法:一种是将土层变形施加在模型边界模拟地震作用;另一种是将土层加速度施加到整个模型上模拟地震作用。这两种简化分析方法都避免了反应位移法中弹簧刚度的取值问题,提高了计算效率。其次分析不同地震动强度、不同侧边距的计算结果,并用动力时程分析的计算结果校核,分析两种简化计算方法的精度。结果表明:随着地震动强度的增加两种简化分析方法的计算结果都令人满意,使用强制反应位移法时建议侧边距取两倍结构宽度,使用反应加速度法时建议侧边距取三倍以上结构宽度。 相似文献
18.
本文采用子空间迭代法分析了单层膜型网壳结构的自振特性;推导了大跨空间结构几何非线性地震响应时程分析的计算过程,编制相应的计算程序,用振型分解反应谱法与时程法进行了结构地震响应特性分析。研究表明:膜型网壳结构的抗震性能比较好;用反应谱法分析时,水平地震作用下截断振型取15、竖向地震作用下取60可满足工程设计要求;用反应谱法计算结构竖向地震响应是安全可靠的,但进行水平地震响应分析时,最终还需用时程法进行验算。 相似文献
19.
In this paper, a nonlinear stochastic seismic analysis program for buried pipeline systems is developed on the basis of a probability density evolution method (PDEM). A finite element model of buried pipeline systems subjected to seismic wave propagation is established. The pipelines in this model are simulated by 2D beam elements. The soil surrounding the pipelines is simulated by nonlinear distributed springs and linear distributed springs along the axial and horizontal directions, respectively. The joints between the segmented pipes are simulated by nonlinear concentrated springs. Thereafter, by considering the basic random variables of ground motion and soil, the PDEM is employed to capture the stochastic seismic responses of pipeline systems. Meanwhile, a physically based method is employed to simulate the random ground motion field for the area where the pipeline systems are located. Finally, a numerical example is investigated to validate the proposed program. 相似文献