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A study on ground-motion amplification and wave-propagation characteristics in a sedimentary basin

沉积盆地地震动放大及波传播特性研究

基本信息

批准号：
15560411
负责人：
TOSHINAWA Takumi
金额：
$ 2.43万
依托单位：
Meisei University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

Strong-motion observation and microtremor measurements were carried out in order to investigate ground-motion and wave-propagation characteristics. The research field concerned herein is Kofu basin which is located in the western part of the Tokyo Metropolitan area. As of April 2004,over 150 events including 2004 Niigataken-chuetsu, 2003 Miyagiken-oki earthquakes have been observed by strong-motion stations deployed in the field. The strong-motion observations indicate that larger amplification and longer duration of strong motions were observed on sedimentary basin in comparison to on mountains and hills. The observation also indicates that amplification and duration of strong motion depends on the magnitude of earthquakes because larger earthquakes contain long-period components while smaller earthquakes contain short-period components. Microtremor observations for long-period components were carried out in 2003 and 2004,with the number of total observation points is about 260. They indicate that natural period of the deep sedimentary layer ranges about 1 to 8 sec and is shorter in the northern part of the basin and the period becomes longer as it goes southward. On the alluvial fen area which consists of thick gravel, marked natural period cannot be found. This is probably because there is less high velocity contrast between the surface layer and basement on such area. From the distribution of natural period and the quarter-wavelength law, the thickness of the deep sedimentary layer is estimated, to be from 0.5 to 2km.

为了研究地面运动和波的传播特性，进行了强震观测和微动测量。本文的研究对象是位于东京都西部的甲府盆地。截至2004年4月，在现场部署的强震台站已经观测到包括2004年新泻县中越地震、2003年宫城县冲地震在内的150多起地震。强震观测结果表明，沉积盆地上的强震比山地和丘陵上的强震放大幅度大，持续时间长。观测还表明，强震的放大和持续时间取决于地震的震级，因为较大的地震包含长周期分量，而较小的地震包含短周期分量。2003年和2004年进行了长周期分量的地脉动观测，共观测点约260个。结果表明，盆地深部沉积层的自然周期为1 ~ 8秒，盆地北方段自然周期较短，向南自然周期变长。在由厚砾石组成的冲积沼泽区，没有发现明显的自然周期，这可能是由于该地区的表层与基底之间的高速反差较小。根据自然周期的分布和四分之一波长定律，估算出深层沉积层的厚度为0.5 ~ 2km。