A Study on Characteristics of Strong Ground Motions from the 2003 Tokachi-oki Earthquake

2003年十胜大地震强地震动特征研究

• 批准号: 16310120
• 负责人: SASATANI Tsutomu
• 金额: $ 6.66万
• 依托单位: HOKKAIDO UNIVERSITY
• 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
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16310120/
• 关键词: 2003 Tokachi-oki Earthquake; Long-period seismic wave; Non-linear soil response; Velocity response; Source effect; Propagation path effect; Basin surface wave; attenuation relationship; 地下構造調査; 最大地動速度; 微動アレー観測; 非線形地震応答; 最大地動加速度; 計測震度; 速度応答スペ

The 2003 Tokachi-oki earthquake, a great interplate earthquake (Mw8.3), is the first M8 class earthquake in Japan since the dense strong-motion networks such as the K-NET and KiK-net have been deployed. We examine spatial distributions of velocity responses (damping factor h=0.05) with various natural periods for this earthquake by using the dense strong-motion network data. The short-period (T=0.1sec; T=natural period) velocity response distribution shows a typical feature for subduction-zone earthquakes; the high response values are observed along the Pacific coast of north Japan. This feature is explained by the S-wave attenuation structure beneath north Japan; that is, the path effect. On the other hand, the long-period (T=20sec) velocity response distribution shows a peculiar feature: at comparable distance, the response values in the northern part of the epicenter are higher than those in the south-western part. This peculiar feature is mainly explained by the source effect; the radiation pattern of long-period Rayleigh waves.We find various types of the site effects. A remarkable one is excitation of long-period basin surface-waves at large plains with thick sedimentary layers. The other remarkable one is nonlinear site response. We find mild nonlinear site response at a soft soil site located on flood plain deposits; the nonlinearity is confirmed by comparing the transfer functions for weak and strong motions using the downhole array data. The distinctive nonlinearity is also observed at a not-so-soft soil site located on reclaimed land during the largest aftershock; the accelerogram shows a spiky waveform.

2003年十胜大地震，即板间大地震（Mw8.3），是日本自部署K-NET和KiK-net等密集强震网络以来首次发生M8级地震。我们利用密集的强震网络数据研究了本次地震不同自然周期的速度响应（阻尼因子 h=0.05）的空间分布。短周期（T=0.1秒；T=自然周期）速度响应分布显示了俯冲带地震的典型特征；在日本北部的太平洋沿岸观察到高响应值。这一特征可以通过日本北部下方的 S 波衰减结构来解释；即路径效应。另一方面，长周期（T=20sec）速度响应分布呈现出一个独特的特征：在可比距离上，震中北部的响应值高于西南地区的响应值。这种奇特的特征主要是由源效应来解释的；长周期瑞利波的辐射图。我们发现了各种类型的场地效应。一个显着的例子是在具有厚沉积层的大平原上激发长周期盆地表面波。另一个值得注意的是非线性现场响应。我们在位于洪泛平原沉积物上的软土场地发现了轻微的非线性场地响应；通过使用井下阵列数据比较弱运动和强运动的传递函数来确认非线性。在最大的余震期间，在位于填海土地上的不太松软的土壤地点也观察到了独特的非线性；加速度图显示尖峰波形。