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Tokachi-Oki地震是一场巨大的板间地震（MW8.3），是日本的第一次M8级地震，因为已经部署了诸如K-NET和KIK-NET之类的密集强度网络。我们通过使用密集的强度运动网络数据检查了速度响应（阻尼因子H = 0.05）的空间分布（阻尼因子H = 0.05）。短周期（t = 0.1秒; t =自然时期）速度响应分布显示了俯冲区域地震的典型特征。在日本北部的太平洋海岸观察到了高响应值。日本北部下方的S波衰减结构可以解释此功能。也就是说，路径效应。另一方面，长周期（t = 20秒）速度响应分布显示一个特征：在可比的距离下，震中北部的响应值高于西南部分的响应值。这种特殊的特征主要由源效应解释。长期雷利波的辐射模式。我们找到各种类型的位点效应。一个了不起的是，在大平原上激发长周期盆地表面波，具有厚厚的沉积层。另一个显着的是非线性站点响应。我们发现位于洪水平原沉积物上的软土位处的轻度非线性部位响应。通过使用井下阵列数据比较弱和强运动的传递函数来确认非线性。在最大的余震期间，位于回收的土地上的一个不那么宽敞的土壤地点也观察到了独特的非线性。加速图显示了尖峰波形。