Strong ground motionsimulation using dynamic rupture model and application to the historical earthquake

利用计算机模拟研究了走滑断层附近强地震动的性质。在均匀弹性半空间或层状半空间中，断裂过程用固定破裂速度的应力释放来模拟。采用交错网格四阶三维有限差分法计算了断层上的地震动和滑动历史。假定断层破裂从一点开始，以0.8倍剪切波速作圆周传播。本文主要研究地震动速度矢量的空间分布，即强震的方向。在双向破裂传播的情况下，在断层中心附近出现较强的断层平行地震动，在断层边缘附近出现断层地速度的正向运动;在单向破裂传播的情况下，在起点附近出现断层平行地震动，但幅度小于双向破裂传播的情况。在破裂终点附近，断层的正向运动占主导地位。将所得结果应用于1927年Tango地震、1930年北伊豆地震和1948年福井地震的震害数据，特别是简单物体倾覆和木屋倒塌的方向数据，发现方向数据的空间分布反映了震源过程产生的强地面运动。

Computer simulation was used to study the nature of the strong ground motion near the strike slip fault. The faulting process was modeled by stress release with fixed rupture velocity in a uniform elastic half-space or layered half space. The fourth-order 3D finite difference method with staggered grids was employed to compute both ground motions and slip-histories on the fault. The fault rupture was assumed to start from a point and propagate circularly with 0.8 times shear wave velocity. In the present paper, we focused on the spatial pattern of ground velocity vectors I.e. the direction of strong motions. In the case of bilateral rupture propagation, the strong fault parallel ground motion appeared near the center of the fault.The fault normal motions of ground velocity appeared near the edges of the fault.In the case of unilateral rupture, the fault parallel motion appeared near the starting point but the amplitude was lower than that for the bilateral rupture case. The fault normal motion was predominant near the terminal point of the rupture. The results were applied to the earthquake damage data, especially the directions that simple bodies overturned and wooden houses collapsed caused by the 1927 Tango, the 1930 Kita-Izu, and the 1948 Fukui earthquakes.The spatial distributions of the direction data were found to reflect the strong ground motions generated from the earthquake source process.