Advanced prediction of long period ground motion in Osaka during huge subduction earthquakes

Tonankai和Nankai地震的发生率有很大的可能性，因为它能够造成巨大的伤害，造成位于大盆地的Mega-City Osaka。在这项研究中，我们试图通过基于源建模的验证验证的配方对地面运动预测、传播路径效应的估计来推进长时间的地面运动预测。我们展示了对源建模是否从回收应用到实际地震的验证（2003年Tokachi-oki地震和2005年Miyagiken-oki地震）。根据记录的理论长周期地面运动模拟，我们提出Q=f·Vs/2作为波形模拟中的最佳Q值使用三维有限差异方法进行波形模拟。最后，我们在大Mega-City使用三维有限差异方法来预测预期的Tonankai和Nankai地震。预测的长周期地面运动的特征与源头位置和盆地的沉积物的厚度有关。地面运动的前阶段是在厚厚的边缘地区4至6秒，在薄的边缘地区3至4秒（底部边缘）。大市中心部分的长期地面运动时间比4分钟多，而前阶段大约有6秒钟。这些结果提出了我们需要调查高风险建筑物和基础隔离建筑物的地震安全，而且是这样的。

There is high possibility of the occurrence of the Tonankai and Nankai earthquakes which are capable of causing immense damage to mega-city Osaka which located inside the Osaka basin. In this study, we tried to advance the long period ground motion prediction through the verification of the source modeling based on the recipe for the ground motion prediction, estimation of propagation path effect. We showed the validation of the source modeling due to the recipe from application to the actual earthquakes (2003 Tokachi-oki earthquake and 2005 Miyagiken-oki earthquake). Furthermore, from theoretical long period ground motion simulation of the recordings, we proposed Q=f・Vs/2 as the optimum Q value in waveform simulations using 3-D Finite Difference Method. Finally, we carried out long period ground motion prediction in mega-city Osaka using the 3-D finite difference method for the expected Tonankai and Nankai earthquakes. The characteristics of the predicted long-period ground motions are related with the source location and the thicknesses of the sediments of the basin. The predominant period of ground motions is 4 to 6 second in the thick sediment area, 3 to 4 second in the thin sediment area (basin edge). The durations of long period ground motions in the central part of the Osaka city are more than 4 minutes, and the predominant period is around 6 second. These results suggest that we need to investigate the seismic safety of high-rise buildings and base-isolated buildings and so on.