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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.

1948年福井地震时，大部分重灾区集中在覆盖着厚厚第四纪沉积物的福井平原。这表明沉积结构可能是阐明损伤分布的最重要因素之一。首先，我提出了一种基于地震观测记录的地下结构反演方法，假设垂直传播的SH波在水平分层系统中进行多次反射。该过程被表述为一个优化问题，以找到每层的厚度和 Q 值，从而最大限度地减少计算和测量的傅立叶光谱之间的差异。将这种反演程序应用于福井平原中心部署的台站观测到的实际强震记录，我计算了平原下方直至第三系的二维横波速度结构。经证实，所识别的地下结构在监测响应和计算响应之间具有相当好的一致性，并且估计的结构与 PS 测井数据和 P 波反射测量相一致。基于微震观测，探索了福井平原周围的次级三维第四纪构造。对覆盖福井痛的每个小网格进行了地表的微震观测。从收集的傅里叶和 H/V 光谱中指定每个位点的主要周期和 H/V 比。通过假设S波速度结构，根据主导周期估算了遗址第四系的厚度。通过将该程序应用于地面条件数据很少的地点，人们可以非常准确地预测强烈的地震响应。