Anomalous Propagation of Long-Period Ground Motions Recorded in Tokyo during the 23 October 2004 Mw 6.6 Niigata-ken Chuetsu, Japan, Earthquake
Anomalous Propagation of Long-Period Ground Motions Recorded in Tokyo during the 23 October 2004 Mw 6.6 Niigata-ken Chuetsu, Japan, Earthquake
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DOI：
10.1785/0120060166
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发表时间：
2007-06
影响因子：
3
通讯作者：
T. Furumura;T. Hayakawa
中科院分区：
文献类型：
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作者：
T. Furumura;T. Hayakawa
2004 年 10 月 23 日新泻县中越 6.6 级地震期间，东京市中心观察到异常大（5 厘米）且持续的震动，与周期约 7 秒的长周期地震动有关。长周期地震动在约 70 层高的高层建筑中引起了显着的共振。因此，了解东京大地震相关长周期地震动的发展和放大特性是当务之急。在这项研究中，我们使用了全国加速度计网络（K-NET、KiK-net）中 585 个站的大量波形记录以及东京周边地区的 495 个强度计。数据显示，长周期地震动的大部分特征是在关东盆地北缘产生的表面瑞利波，表面波是通过坚硬基岩上厚厚的沉积物（3000-4000 m）传播而发展起来的。为了补充观测数据，我们利用地球模拟器超级计算机，利用详细的源滑移模型和日本中部的高分辨率3D沉积构造模型，对地震波传播进行了大规模计算机模拟。计算机模拟结果表明，东京市中心记录的长周期信号出现异常长时间的地面震动，是由于瑞利波从周围山区向关东盆地底部的多径传播和聚焦，与3D盆地结构相互作用，导致地震能量停滞所致。
Unusually large (5 cm) and prolonged shaking associated with long- period ground motions at periods of about 7 sec were observed in central Tokyo during the Mw 6.6 Niigata-ken Chuetsu earthquake of 23 October 2004. The long- period ground motions caused significant resonance in high-rise buildings of about 70 floors in height. Thus, it is an urgent matter to understand the development and amplification properties of long-period ground motions in Tokyo associated with large earthquakes. In this study, we use numerous waveform records from 585 stations in a nationwide accelerometer network (K-NET, KiK-net) and 495 intensity meters in the area around Tokyo. The data reveal that the long-period ground motion is characterized in most part by a surface, Rayleigh wave generated at the northern edge of Kanto basin, and the surface wave is developed as propagating through a thick cover of sediments (3000-4000 m) that overlies rigid bedrock. To complement the observational data, we conducted a large-scale computer simu- lation of seismic-wave propagation by employing the Earth Simulator supercomputer with a detailed source-slip model and a high-resolution 3D sedimentary structural model of central Japan. The results of the computer simulation demonstrate that the anomalously prolonged ground shaking of the long-period signal recorded in the center of Tokyo occurred because of the stagnation of seismic energy resulting from the multipathing and focusing of Rayleigh waves toward the bottom of the Kanto basin from surrounding mountain regions with interaction to the 3D basin structure.