Investigation of shallow to deep subsoil structures in urban area by means of microtremors and its application to an assessment for regional seismic input motions.

利用微震研究城市地区浅层到深层地下结构及其在区域地震输入运动评估中的应用。

基本信息

批准号：
02452207
负责人：
KAGAMI Hiroshi
金额：
$ 3.65万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-02452207/
关键词：
Microtremors Seismic baserock Ishikari Plain Spectral analysis Site effect Tree dimensional model

项目摘要

The purpose of this study is to develop a feasible method for evaluating seismic input motions in an urban area by means of experimental way and Sapporo urban area, northern Japan, was selected as a test field.Microtremors measurement was adapted for this study because of its easy applicability for detecting subsoil conditions. At the first, the observation system was upgrading in both terms of hardware and software. An A/D converter was installed in a laptop computer and a real time monitoring was introduced by computer program. With this system daytime measurements in busy business district can be performed in spite of low S/N ratio.Extensive measurements of long-period microtremors were conducted in Sapporo urban area in 1990 and 1991. Seven observation lines parallel to the coastal line and two lines perpendicular to these were set up, covering the area of about 40 x 40 kilometers, obtaining records at totally 183 sites. One reference site was set up at Hokkaido University to monitor the time variation of microtremors during the period of measurements.Spectral ratios were obtained for each site by dividing the Fourier spectra by the corresponding spectra at the reference site. These ratios were plotted on a map for each period of 0.5, 1, 2 and 4 second and four contour maps were drawn as seismic microzonig maps. These maps were verified by various of small number of deep drilling data, three strong motion records and seismic intensity distribution data of the 1982 Off-Urakawa earthquake.

这项研究的目的是开发一种可行的方法来通过实验方式评估城市地区的地震输入运动，而日本北部的萨波罗市区被选为测试场。Microtretremors的测量之所以适用于本研究，是因为它容易适用于检测高层土壤条件。首先，观察系统在硬件和软件方面都在升级。在笔记本电脑中安装了A/D转换器，并通过计算机程序引入了实时监视。尽管S/N比率较低，但可以在繁忙的商业区进行此系统日间测量。长期的较长型微型植物的扩展测量是在1990年和1991年在萨波罗市区进行的。平行于沿海地区的七个观察线，与沿海地区平行，垂直于这些线路垂直于两行，覆盖了大约40 x40 x40 k的区域，完全占据了40千米的录制。在北海道大学建立了一个参考位点，以监视测量期间微生物的时间变化。通过将傅立叶光谱除以参考位点的相应光谱，从而获得了每个位点的光谱比。将这些比率绘制在每个周期的0.5、1、2和4秒和四个轮廓图的地图上，并作为地震微量年图绘制。这些地图通过少量深钻数据，三个强运动记录和1982年乌拉川地震的地震强度分布数据进行了验证。