Destructive strong motion estimation during the old inland large earthquakes based on empirical heterogeneous source model

预测强地震动的不确定性主要在于模拟未来地震的震源非均质性。我们提出了一种描述断面上非均匀滑动分布的有效方法，该方法基于Somerville等人（1999）从地壳地震滑动模型中得出的经验震源特征。具有较大滑动的凹凸不平区域是根据从超过1秒的地面运动记录的波形反演中得到的滑动模型来定义的。利用这种方法，我们可以确定断层表面具有均匀滑动的凸起，其大小受地震的整个地震矩的约束。我们需要通过对宽带强地面运动的模拟来研究粗糙度模型的有效性。本文通过对1945年日本三川地震和2000年日本鸟取县仙部地震的强震运动模拟，验证了由若干凸起和背景（非凸起）组成的震源模型在强震预报中的有效性和适用性。在三川地震的模拟中，我们得到了合成峰值速度和仪器地震烈度的分布与观测到的木制房屋倒塌率估计的地震烈度分布大致对应。合成波形的峰值速度接近150 cm/sec，与1995年兵库县南部地震和1948年福井地震基本一致。结果表明，该模型可用于估计宽带强地面运动，并且强度为7的破坏性强运动的速度幅值大于150 cm/sec。

Most of the uncertainties in predicting strong ground motion is to model source heterogeneities of future earthquakes. An available method we propose for characterizing the heterogeneous slip distribution on the fault plane is based on the empirical source characterization derived from the slip models of the crustal earthquakes by Somerville et al. (1999). Areas of asperities having large slips are defined based on the slip models derived from waveform inversion of longer ground motion recordings than 1 second. Using this method, we can specify asperities with uniform slip on the fault surface whose sizes are constrained by the entire seismic moment of an earthquake. We need to investigate the effectiveness of the asperity models through the simulations of broad-band strong ground motions. In this study, the validity and applicability of the source models composed of some asperities and background (off asperities) for strong ground prediction are examined through the simulation of strong ground motions during the 1945 Mikawa earthquake and the 2000 Tottori-ken Senbu earthquake in Japan.In the simulation of the Mikawa earthquake, we have obtained that the distributions of the synthetic peak velocity and instrumental seismic intensity roughly correspond to the distribution of the seismic intensity estimated from the observed collapse ratio of wooden houses. Furthermore, the peak velocity of the corresponding synthetic waveform is close to 150 cm/sec, and compatible to the 1995 Hyogo-ken Nanbu earthquake and the 1948 Fukui earthquake.Resultantly, we found that the asperity models are available for estimating broad-band strong ground motions, and that the destructive strong motions in the area of the intensity 7 have velocity amplitude larger than 150 cm/sec.