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年的福岛地震期间，大多数受损坏的地区集中在福岛平原上，上面覆盖着厚实的第四纪沉积物。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，我提出了一个基于地震观察记录的地下结构的反转程序，假设在水平分层系统中垂直传播的sh波的多反射。该过程被公式化为优化问题，以找到每一层的厚度和Q值，从而最小化计算的傅立叶光谱和测量傅立叶光谱之间的不同之处。将这种反转程序应用于在福岛平原中心部署的站点观察到的实际强烈地震记录，我计算了平原下至第三纪的2d S波速度结构。据证实，已确定的地下结构在监视和计算的响应之间提供了相当良好的一致性，并且估计的结构与PS-Logging数据和P-波 - 反射调查进行了协调。基于微生物观察，探索了福岛平原周围的二维四维第四纪结构。在地面上进行了微晶状体观测，进行了覆盖福克疼痛的每个小网格。从收集的傅立叶和H/V光谱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，根据主要时期估算了位点的第四纪系统的厚度。通过将程序应用于几乎没有地面条件数据的位置，人们可能能够以良好的精度预测强烈的地震响应。