Simulation Analysis of Strong Motions in the Ashigara Valley Considering One- and Two-Dimensional Geological Structures.
Simulation Analysis of Strong Motions in the Ashigara Valley Considering One- and Two-Dimensional Geological Structures.
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考虑一维和二维地质结构的足柄山谷强运动模拟分析。
DOI：
10.4294/jpe1952.40.27
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Toshiaki Sato
中科院分区：
文献类型：
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作者：
H. Kawase;Toshiaki Sato
在日本Ashigara山谷软沉积物上观测到的加速波显示了表面波在山谷内部传播的清晰证据。我们试图通过使用山谷的二维地质结构和在围岩上观测到的加速度来模拟这些观测到的加速度。首先，对观测记录进行了检验，以确认在s波到达后19或25秒出现的孤立后期相是由盆地诱发的表面波引起的，表面波是由入射体波在盆地边缘转换而来的。然后应用一维波传播理论验证了假设土性的正确性。软质沉积物上记录的前30秒加速度与一维模拟结果吻合较好，后30秒加速度与一维模拟结果不符。因此，基于现有的地质和地球物理资料，假设盆地的边界形态和性质，采用二维有限元方法进行盆地模型分析。计算结果表明，这种二维模型可以产生缓慢穿过盆地的表面波。Love波的振幅大于Rayleigh波的振幅，这与我们观察到的一致。然而，后期的相对振幅比观测到的要小，主导周期也比观测到的短。为了在没有试错调整的情况下进行更多的定量模拟，土壤性质的详细信息，特别是S波速度和软沉积物的质量因子是至关重要的。
Accelerograms observed on the soft sediments of the Ashigara Valley, Japan show clear evidence of surface wave propagating inside the valley. We try to simulate these observed accelerograms by using a two-dimensional geological structure of the valley and accelerograms observed on surrounding rock. First, observed records are examined to confirm that the isolated later phases that emerge 19 or 25 s after the S wave arrival are due to the basin-induced surface wave, the surface wave converted from the incident body wave at the edge of the basin. Then one-dimensional wave propagation theory is applied to check the appropriateness of the assumed soil properties. The first 30 s of the accelerograms recorded on the soft sediments show very good agreement with the one-dimensional simulation results, but the later part does not. Therefore a two-dimensional finite element method is used for a basin model whose boundary configuration and properties are assumed based on available geological and geophysical data. The calculated responses show that this two-dimensional model can generate surface waves which travel across the basin very slowly. The amplitude of the Love wave is greater than that of the Rayleigh wave, which is in accordance with what we observe. However, the relative amplitude of the later phase is smaller and the predominant period shorter than the observed. For more quantitative simulation without trial-and-error adjustment detailed information of the soil properties, especially S wave velocities and quality factors of the soft sediments, are crucial.