An advanced Research on the Structural Dynamics due to Short-Period Surface Waves with Emphasis on Applications to Practice

我们开发了一些应用伪谱法分析水平不规则地基地震反应的软件。特别强调了土壤非线性特性的介绍以及程序的复杂性。为了将我们的软件应用于实践，我们选择了仙台市的不规则场地作为测试场地。仙台市在1978年宫崎地震中遭受了严重的破坏。自地震以来，仙台市已经扩展到土壤较软的地区，这增加了人们对不久的将来发生大地震的破坏性灾难的担忧。为了调查仙台地区的强震，我们于1997年在那里安装了地面震动阵列观测系统。这个名为“小泰坦”的阵列系统由20个观测站和一个控制中心组成。受仙台地区高地震活动性的刺激，该系统获得了截至2004年2月共250次地震的许多运动记录。本文首先从局地效应的角度对仙台盆地地震动观测结果进行了讨论，结果表明，不同地点的地震动放大程度不同，在盆地软沉积区地震动放大程度显著。分析了软沉积区不同位置间的放大差异。由此得出盆地构造的边缘效应对软沉积区地面运动的重要性。为了明确边缘效应的作用机制，采用二维伪谱方法对仙台盆地进行了模拟。以盆地构造模型为基础，进行了二维地震动分析，并将分析结果与观测结果进行了比较。对比表明，在盆地构造软沉积区，边缘效应在放大运动中起着重要作用。

We have developed, some softwares for the earthquake response analysis of horizontally irregular grounds using the Pseudo-spectural method. Especially emphasis was placed on the introduction of nonlinear characteristics of soils as well as on the sophistications of programs. For the purpose of applications of our softwares to practice, we selected the irregular ground in Sendai City as a test site. Sendai City suffered severe damage due to the 1978 Miyagiken-Oki Earthquake. Since the earthquake, Sendai City has extended into areas composed of softer soils, increasing the anxieties of more devastating disaster by a great earthquake in the near future. In order to investigate strong-ground motions in Sendai, we installed there an array observation system of ground motions in 1997. The array system, named Snall-Titan, consists of 20 observation stations and one control center. Stimulated by the high seismicity in the Sendai district, the system has obtained many motion records resulting from a total of 250 earthquakes as of February in 2004. We first discussed observation results of ground motions in the Sendai basin from the point of view of local site effects, showing that amplifications of ground motions vary from site to site and arc remarkable in the soft deposit areas of the basin. The differences in amplifications between locations of the soft deposit areas were also analyzed. This analysis led to the importance of the edge effects of basin structure on the ground motions of the soft deposit areas. In order to make clear the mechanism of the edge effects, we modeled the Sendai basin using a two-dimensional Pseudo-Spectral Method. Based on-the model of basin structure, we made two-dimensional analyses of ground motions and compare the analyzed results with the observed. Comparisons show that the edge effects play an important role in amplifying motions in the soft deposit area of basin structure.