A simplified method for simulation of strong ground motion using finite rupture model of the earthquake source

We present a simplified method to simulate strong ground motion for a realistic representation of a finite earthquake source burried in a layered earth. This method is based on the stochastic simulation method of Boore (Boore, D. M., 1983, Bull. Seism. Soc. Am. 73, 1865–1894) and the Empirical Greens Function (EFG) method of Irikura (Irikura, K., 1986, Proceedings of the 7th Japan Earthquake symposium, pp. 151–156). The rupture responsible for an earthquake is represented by several subfaults. The geometry of subfaults and their number is decided by the similarity relationships. For simulation of ground motion using the stochastic simulation technique we used the shapping window based on the kinetic source model of the rupture plane. The shaping window deepens on the geometry of the earthquake source and the propagation characteristics of the energy released by various subfaults. The division of large fault into small subfaults and the method for accounting their contribution at the surface is identical to the EGF. The shapping window has been modified to take into account the effect of the transmission of energy released form the finite fault at various boundaries of the layered earth model above the source. In the present method we have applied the correction factor to adjust slip time function of small and large earthquakes. The correction factor is used to simulate strong motion records having basic spectral shape of ² source model in broad frequency range. To test this method we have used the strong motion data of the Geiyo earthquake of 24th March 2001, Japan recorded by KiK network. The source of this earthquake is modelled by a simple rectangular rupture of size 24 × 15 km, burried at a depth of 31 km in a multilayered earth model. This rupture plane is divided into 16 rectangular subfaults of size 6.0 × 3.75 km each. Strong motion records at eight selected near-field stations were simulated and compared with the observed records in terms of the acceleration and velocity records and their response spectrum. The comparison confirms the suitability of proposed rupture model responsible for this earthquake and the efficacy of the approach in predicting the strong motion scenario of earthquakes in the subduction zone. Using the same rupture model of the Geiyo earthquake, we compared the simulated records from our and the EGF techniques at one near-field station. The comparison shows that this technique gives records which matches in a wide frequency range and that too from simple and easily accessible parameters of burried rupture.     

钱塘江河口盐度数值模拟

强潮河口盐水入侵对饮用水源地危害极大。基于平面二维水动力盐度模型, 对典型强潮河口—钱塘江的水动力及盐水入侵过程进行了数值模拟研究。结果表明枯水径流时盐度变化与潮位过程曲线类似, 潮差对盐度大小影响显著, 径流量的增加将逐渐减小其相似程度。当流量增加到一定程度后, 继续增加的一定径流量所产生的抑咸效果减弱, 水资源有效利用率降低, 此时允许水源地盐度超标并改从蓄淡避咸水库取水可有效节约水资源。盐度平面分布显示, 盐水入侵在强潮河口弯道处受涨潮流主流线影响明显, 靠近主流线一岸的盐度大于对岸, 单从盐水入侵角度考虑, 强潮河口弯道段的取水口应设置在远离涨潮流主流线一岸。钱塘江河口盐度数值模拟对于研究减轻盐水入侵对水源地危害的措施具有指导意义。     

重庆地区夏季一次降水过程及增雨潜力的数值模拟分析

利用国家气象中心GRAPES人工增雨云系模式,选取2008年7月4日重庆地区一次降水过程进行数值模拟,分析了重庆地区降雨天气的水汽分布、云系宏微观分布、云中微物理转化和增雨潜力等特征。结果表明：本次降水大气过程中,重庆地区水汽含量极为丰富,水汽分布与地形分布呈明显的对应关系,低层水汽输送较大,整层水汽通量较高,有明显水汽辐合,云中液态水对地面降水影响很大。西南气流和地形共同作用为重庆地区液态水的形成提供了有利条件,在东北部山区迎风坡处大量水汽累积抬升,易形成丰富的液态水。重庆东北部地区水汽向云水转化较强,过冷液态水含量丰富,冰晶含量少,0℃层附近水汽垂直通量较大,降水效率较低,有较大的增雨潜力。     

2009年豫南一次强暴雨过程的位涡方程诊断分析

利用中尺度WRF模式、NCEP/NCAR再分析格点资料及常规气象观测资料,对2009年8月28—30日河南省南部一次强暴雨过程进行中尺度数值模拟,借助模式输出的模拟数据计算位势涡度及位势涡度方程收支,并利用位涡收支方程对此次暴雨过程进行诊断分析。结果表明,WRF模式对此次暴雨过程的模拟效果较好,模拟暴雨强度及落区与实况较一致,位势涡度能够较好地反映此次暴雨过程的动力及热力特征。位涡异常高值区与暴雨中心有较好的对应关系,暴雨中心大致位于位涡高值中心东南侧。位涡收支方程中各收支项同样能够反映此次暴雨过程的动力、热力性质。暴雨发展过程中大气中低层位涡局地增加,位涡局地变化大值中心驿应暴雨中心。各收支项中,引起中低层位涡局地变化的贡献主要来源于潜热加热作用、水平平流作用、垂直输送作用及摩擦作用。其中潜热加热与水平平流作用对暴雨中低层正变位涡起正贡献作用,潜热加热作用有利于位涡局地增加,水平平流作用易于低层位涡向流场辐合区聚集,引起局地位涡增加;垂直输送及摩擦作用对中低层位涡变化表现为负贡献作用,垂直作用易于将中低层位涡向高层输送,使得低层位涡减小,高层位涡增加。在摩擦作用下,低层位涡被大量耗散,使得中低层位涡局地减小。     

Toward micro-scale spatial modeling of gentrification

 A simple preliminary model of gentrification is presented. The model is based on an irregular cellular automaton architecture drawing on the concept of proximal space, which is well suited to the spatial externalities present in housing markets at the local scale. The rent gap hypothesis on which the model's cell transition rules are based is discussed. The model's transition rules are described in detail. Practical difficulties in configuring and initializing the model are described and its typical behavior reported. Prospects for further development of the model are discussed. The current model structure, while inadequate, is well suited to further elaboration and the incorporation of other interesting and relevant effects. Received: 1 November 2001 / Accepted: 12 April 2002 Town centres data were made available by kind permission of the UK Department of the Environment, Transport and the Regions.     

利用ARC/INFO进行三维地形模型的建立、处理和动态模拟

介绍了利用 ARC/ INFO建立三维地形模型的方法 ,以及利用其新版本的部分新功能处理三维地形模型、进行动态模拟的方法 ,与以往处理三维模型必须借助外部三维图形开发软件包的方法相比 ,具有高速、灵活、可视性强、支持强大分析功能等优点。形成的三维模型可随时与 ARC/ INFO的其它数据模型交换信息 ,与外部进程实时通讯 ,为使用者提供了二维分析工具所不能提供的信息 ,为开发视景仿真系统等与表面分析、立体显示有关的应用系统提供了强有力的支持。     

防波堤的人工神经网络Monte Carlo法可靠性分析

防波堤建设费用巨大,且一旦遭到破坏,后果甚为严重,因此,如何准确地计算防波堤的可靠性意义重大.随着人工神经网络理论的快速发展,人工神经网络方法在结构可靠性分析中的应用逐渐得到重视.基于神经网络的Monte Carlo法计算直立式防波堤的可靠性,概率意义明确.以秦皇岛典型直立堤为算例,采用基于神经网络的Monte Carlo法对直立式防波堤进行可靠性分析时,将直立堤滑动破坏和倾覆破坏的极限状态方程中的所有参数均作为变量处理,并将计算结果与Monte Carlo模拟的直接抽样法、重要抽样法以及独立变量JC法的计算结果进行对比.结果表明:基于神经网络的Monte Carlo法和Monte Carlo模拟的直接抽样法、重要抽样法计算结果相近,而比独立变量JC法的计算结果略低.     

锦屏电站坝厂区卸荷岩体力学参数研究

选择具有代表性的区块,根据结构面的性状和规模拟定模型层次和尺寸,建立岩体数值仿真模型,通过计算机数值仿真,采用卸荷非线性力学理论对锦屏电站坝厂区岩体进行卸荷岩体宏观力学特性及参数的数值分析;同时,用RMR法和BP神经网络法对岩体宏观力学特性及参数进行分析,综合确定岩体力学参数,为设计部门提供设计参考依据.     

采用土工合成材料的新型护岸结构的动态数值模拟

固化土和土工格栅护岸工法（SG-WALL工法）是一种采用固化土和土工格栅加固港口护岸结构的新型工法。它的抗震性能已经通过一系列振动台试验得到了确认。为了能够数值再现SG-WALL结构在地震荷载作用下的动力反应,对SG-WALL结构的振动台试验进行了动态数值模拟研究。试验和模拟结果的对比表明,数值模拟方法能够再现SG-WALL结构在振动荷载作用下的主要动力特征。模拟结果还表明：固化土的长度对SG-WALL抗震性能起到重要的影响;土工格栅的最大拉应变发生在与排桩的连接处,并且沿着远离排桩的方向逐渐减小。     

建筑基坑土钉支护时机探讨

本文采用FLAC软件，通过建筑物基坑随开挖深度增加而变形的模拟，得出基坑每一阶段开挖及土钉支护条件下的位移发展演变规律，跟踪最大不平衡力变量的变化提出了最佳土钉支护时机。