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Estimation of three dimensional ground structure in Fukui Plain based on inversion analysis of observed ground motion

基于实测地震动反演分析的福井平原三维地面结构估算

基本信息

批准号：
13650518
负责人：
KOJIMA Keisuke
金额：
$ 0.51万
依托单位：
Fukui University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650518/
关键词：
Seismic Observation Microtremor H V Ratio Predominant Period S wave Velocity Sedimentary Structure Inversion 3-dim. Ground Structure 推積構造 3次元地盤構造モデル

项目摘要

During the 1948 Fukui earthquake, most of the heavily damaged areas concentrated in the Fukui plain covered with thick quaternary deposits. This suggests that the sedimentary structure can be one of the most important factors to elucidate the damage distribution. Firstly, I propose an inversion procedure of underground structure based on the earthquake observation records, assuming a multi-reflection of vertically propagating SH-wave in a horizontally layering system. The procedure is formulated as an optimization problem to find the thickness and Q-values of each layer which minimize the different between calculated and measured Fourier spectra. Applying this inversion procedure to the actual strong earthquake records observed at the stations deploying in the center of Fukui plain, I calculated 2D S-wave velocity structure beneath the plain up to the tertiary. It was confirmed that the identified underground structure give a fairly good agreement between monitored and calculated responses, and that estimated structure is harmonized with PS-logging data and P-wave reflection survey. Secondary, 3-dimensional Quaternary structure around Fukui plain was explored based on the microtremor observation. The microtremor observations on the ground surface were carried out every small grid that covered the Fukui pain. Predominant periods and H/V ratios of each site were specified from collected Fourier and H/V spectra. By assuming S wave velocity structures, the thickness of Quaternary system of the sites were estimated based on the predominant periods. By applying the procedure to the sited having little ground condition data, one may be able predict the strong earthquake response with a good accuracy.

在1948年的福井地震中，大部分严重受损的地区集中在覆盖着厚厚的第四纪沉积物的福井平原。这表明，沉积构造可以是阐明损伤分布的最重要因素之一。首先，本文提出了一种基于地震观测记录的地下结构反演方法，假定水平层状介质中垂直传播的SH波存在多次反射。该过程被配制成一个优化问题，以找到每层的厚度和Q值，最大限度地减少计算和测量的傅立叶光谱之间的差异。将此反演方法应用于部署在福井平原中心的台站观测到的实际强震记录，计算了平原下第三系的二维S波速度结构。它被证实，所确定的地下结构给出了监测和计算的响应之间的相当好的协议，估计的结构是协调与PS测井数据和P波反射调查。本文根据地脉动观测资料，探讨了福井平原周围第四纪次生三维构造。地面上的微动观测进行了每一个小网格，覆盖了福井疼痛。从收集的傅立叶和H/V谱中指定每个站点的优势周期和H/V比。通过假设S波速度结构，根据卓越周期估算了场地第四系厚度。将该方法应用于场地条件资料较少的场地，可以较准确地预测强震反应。