Site Effects Derived from Spectral Inversion Method for K-NET, KiK-net, and JMA Strong-Motion Network with Special Reference to Soil Nonlinearity in High PGA Records
Site Effects Derived from Spectral Inversion Method for K-NET, KiK-net, and JMA Strong-Motion Network with Special Reference to Soil Nonlinearity in High PGA Records
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发表时间：
2006
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通讯作者：
H. Kawase
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作者：
H. Kawase
在这项研究中，我们首先尝试从日本各地观测到的 K-Net、KiK-net 和 JMA 强震动 (Shindo-kei) 网络记录中分离出所谓的源光谱、衰减系数和站点放大因子。作为参考站点，我们使用 KiK-net 的一个岩石站，并使用 +-D 理论放大从记录中删除由风化层引起的非常小的站点效应。一旦我们获得了场地放大系数，我们就尝试获得在**十胜冲地震期间观测到的高 PGA 记录的非线性场地系数，作为观测记录与假设输入基岩运动的比率，该假设输入基岩运动是根据小 PGA（即小于 ** Gals）记录计算得出的平均值。当我们将这些位点效应与较小 PGA 记录的线性位点效应进行比较时，我们发现几个位点显示出比以前研究预期更低的峰值幅度和更低的峰值频率。然而，在一些非常软的位置，我们发现峰值幅度较高，峰值频率较低。这种现象可以解释为阻抗效应（使振幅变高）被非线性增强，并克服了阻尼效应（使振幅变低）。
In this study we first try to separate so-called source spectra, attenuation coe$cient, and site amplification factors from K-Net, KiK-net, and JMA strong-motion (Shindo-kei) network records observed throughout Japan. As a reference site, we use one rock station of KiK-net, and we remove a very small site e#ect caused by weathered layers from the record using +-D theoretical amplification. Once we obtain site amplification factors, we try to obtain nonlinear site factors for high PGA records observed during the ,**Tokachi-Oki earthquake as a ratio of the observed record with respect to the hypothesized input bedrock motion calculated as an average from small PGA (i.e., less than ,** Gals) records. When we compare these site e#ects with linear site e#ects for smaller PGA records, we find that several sites show lower peak amplitude with lower peak frequency than expected from previous studies. However, at a few very soft sites we found higher peak amplitude with lower peak frequency. This phenomenon can be interpreted to occur as the impedance e#ect (makes amplitude higher) is strengthened by nonlinearity, and overcomes the damping e#ect (makes amplitude lower).