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STRONG-MOTION PREDICTION BASED ON THE APPRAISAL OF SUBSURFACE STRUCTURES USING NEW ARRAY METHODS OF MICROTREMOR EXPLORATION

基于微动探测新阵法的地下构造评价的强震动预测

基本信息

批准号：
16360281
负责人：
SHINOZAKI YUZO
金额：
$ 6.02万
依托单位：
TOKYO UNIVERSITY OF SCIENCE
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

In order to realize strong-motion prediction of fine resolution in urban areas, it is desirable to establish simple, economical techniques to explore subsurface soil structures on local scales. The SPAC method is one of such techniques that are considered most promising in recent years. This method consists in measuring microtremors (ambient vibrations) with a circular array of seismic sensors, and in evaluating phase velocity dispersion curves of surface waves by analyzing the records. Once the dispersion curves are known, it becomes possible to indirectly evaluate subsurface soil structures and vibration characteristics of soil.We have found out that, by shedding a new light on the basic theory of the SPAC method, it was possible to devise a number of new circular-array methods of microtremor exploration, and in fiscal 2004 and 2005, we concentrated our efforts on elaborating their theory and making them viable methods for practical use. Among others, two new techniques, which we have named the "Two-Radius method" and the "Centerless Circular Array (CCA) method," respectively, deserve special attention, the former because of its methodological originality that consists in cancelling out all information on Rayleigh waves and extracting information on Love waves alone, and the latter because of its validity over an extremely wide range of wavelengths.In fiscal 2006, we acquired field microtremor records using "miniature" seismic arrays, with radii on the order of 1 meter, and examined whether the different analysis methods could be validly applied to them. It was shown that, by using the CCA method, phase velocities of Rayleigh waves could be inferred with sufficient accuracy up to wavelengths worth about 100 times the seismic array radius. This finding points to the new possibility of inferring deep subsurface soil structures with relative ease, even in urbanized areas with a dense population of artificial obstacles.

为了实现城市地区高分辨率的强震动预报，需要建立简单、经济的局部尺度地下土壤结构探测技术。SPAC方法是近年来被认为最有前途的技术之一。该方法包括用地震传感器的圆形阵列测量微震动（环境振动），以及通过分析记录来评估表面波的相速度频散曲线。一旦知道了频散曲线，就可以间接地评估地下土壤结构和土壤的振动特性。我们发现，通过重新认识SPAC方法的基本理论，可以设计出许多新的微动探测圆阵方法，并在2004年和2005年财政年度，我们集中力量对他们的理论进行了阐述，使他们成为实际应用的可行方法。其中，两种新技术，我们分别命名为“双半径法”和“无心圆阵（CCA）法”，值得特别注意，前者是因为其方法的独创性，包括消除所有信息的瑞利波和提取信息的爱波单独，后者是因为它在极宽的波长范围内有效。在2006财政年度，我们使用半径为1米的“微型”地震阵列获得了现场微动记录，并检验了不同的分析方法是否可以有效地应用于它们。结果表明，通过使用CCA方法，瑞利波的相速度可以推断出足够的精度高达约100倍的地震台阵半径的波长。这一发现表明，即使在人工障碍物密集的城市化地区，也可以相对容易地推断深层地下土壤结构。