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面运动的性质。在均匀弹性半空间或层状半空间中，采用固定破裂速度的应力释放模型来模拟断裂过程。采用交错网格的四阶三维有限差分法计算断层的地震动和滑动历史。假定断层破裂从某一点开始，以0.8倍横波速度圆周传播。本文主要研究地速度矢量的空间分布，即强运动方向。在双侧破裂传播情况下，在断层中心附近出现强烈的断层平行地震动。在断层边缘附近出现了地面速度的断层法向运动。单侧破裂时，断层平行运动在起点附近出现，但振幅小于双侧破裂时。断裂终点附近以断层正向运动为主。将结果应用于1927年的探戈地震、1930年的北伊豆地震和1948年的福井地震造成的地震破坏数据，特别是简单体倾覆和木制房屋倒塌的方向。方向数据的空间分布反映了震源过程产生的强烈地震动。

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.