Estimation of site effects using strong ground motion network data

首先，建立了关西地区强震数据库。数据由Kyoshin-net、CEORKA和科比的时间强震观测组提供。此外，我还收集了这些地点的地质和地球物理地下结构信息。利用这些数据库，我们试图通过反演方法（岩田和入仓，1988）分离场地和源因子以及Q值。得到的Q值与以前的研究结果一致。对于Q值的估计，我们可以只使用岩石和硬土场地的数据集来获得稳定的Q值。垂直分量和水平分量的Q值基本一致，说明垂直分量在地壳中以横波形式传播。S波垂直分量的场地因素与P波垂直分量的场地因素相似，说明S波垂直分量主要由P波组成。其次，对1995年兵库县南部地震时科比大震区及其周边地区的场地因素进行了估算。即使在大地震区，场地因素也各不相同，这说明仅用浅层放大效应不能解释科比大地震的发生。利用K网资料，我们还用小震资料作为经验绿色函数，得到了1997年鹿儿岛县-北西部地震的震源破裂过程。

First, I constructed strong motion data base in Kansai area. Data were provided by Kyoshin-net, CEORKA, and temporal strong motion observation group for Kobe. Also, I collected geological and geophysical underground structure information of the sites. Using these data base, we tried to separate site and source factors and Q-values by the inversion method (Iwata and Irikura, 1988). Obtained Q-values coincide with those by the previous studies. For estimating Q-values, we can obtain the stable Q-values with using data set of only rock and hard-soil sites. Q-values from vertical component of S-waves are consistent with those from horizontal S-wave component and this shows that vertical component of S-waves travel as S-waves in the crust. Site factors of vertical component of S-waves are similar to those of vertical component of P-wave part and this concludes that the vertical component of S-waves is mainly composed by P-waves.Secondly, we estimated site factors in and around large earthquake disaster area in Kobe during the 1995 Hyogoken Nanbu earthquake. Even in the large disaster area, site factors are different among the sites and this shows only superficial layer amplification effects can not explain the large disaster in Kobe.Using K-net data, we also obtained source rupture processes of the 1997 Kagoshimaken-Hokuseibu earthquakes using a small shock data as a empirical Green's function.