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Study on effects of ground surface conditions like irregular shaped ground, trees and buildings on earthquake ground motions

不规则地面、树木、建筑物等地表条件对地震地震动的影响研究

基本信息

批准号：
14380199
负责人：
KAWAKAMI Hideji
金额：
$ 6.27万
依托单位：
Saitama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

The purpose of this study is to clarify the effects of the conditions of the ground surface on the earthquake ground motions. Irregular shaped ground, lots of trees and buildings, which are existing ordinally at the ground surface, were considered in this study. Even if it has been pointed out previously that the ground with an irregular surface may cause complicated seismic responses, the process of generating this complex response has not yet been clarified. In this study, such a process was also examined.Regarding the effects of the irregular ground surface, for example, the seismic responses of ground models with sinusoidal-shaped irregularity, i.e., with various heights and numbers of sinusoidal-shapes, were analyzed. The boundary element method was developed in SH wavefield for numerical analyses, and it was utilized to estimate the frequency response functions at the ground surface. Also, scattered-wave contribution was newly introduced to examine the frequency response functions. The examination of the numerical results revealed the followings :1)the frequency response at the trough varies sharply with frequency, whereas the response at the peak shows large amplification over a wide frequency range ;2)the predominant frequencies at the trough depend on the amplitude of the surface irregularity and do not depend on the number of fluctuations of the ground ; and3)these characteristics can be understood as the results of the interference of scattered waves coming from the irregular surface.

本研究的目的是阐明地面条件对地震动的影响。研究中考虑了不规则形状的地面，大量的树木和建筑物，它们在地面上有序地存在。即使先前已经指出具有不规则表面的地面可能引起复杂的地震响应，但是产生这种复杂响应的过程尚未被阐明。在本研究中，也对这一过程进行了研究。关于不规则地面的影响，例如，具有正弦形不规则性的地面模型的地震反应，即，具有不同的高度和数量的正弦形状，进行了分析。在SH波场中发展了边界元法进行数值分析，并利用边界元法估计了地表的频率响应函数。此外，散射波的贡献是新引入的频率响应函数检查。对数值结果的检验表明：（1）波谷处的频率响应随频率变化剧烈，而波峰处的响应在很宽的频率范围内表现出很大的放大作用：（2）波谷处的优势频率与地表起伏的幅度有关，而与地面起伏的次数无关; 3）这些特征可以理解为来自不规则表面的散射波干涉的结果。