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使用三维有限差分法模拟了由浅走滑断层破裂过程产生的强地面运动。此破裂过程是用一种具有固定破裂速度的裂纹模式来模拟的。还研究了与断层位置和震源参数(像应力降或破裂速度)相关的峰值地动速度图象的变化。我们的发现表明,这些图象受到破裂方向和断层或凹凸体最上部所在深度的强烈影响。当断层突破地表时,峰值地动速度和峰值地动加速度显示出狭窄的强运动区域。当断层隐伏在地下时,平行于断层的高峰值地动速度分量所在的区域距断层迹线有一段与断层深度相当的距离。另一方面,垂直于断层的峰值地动速度则是沿断层迹线最大。断层长度(或凹凸体长度)对峰值地动速度并无太大影响。对有关应力降和破裂速度的非均匀性对强地面运动的影响也作了研究。当应力降不均匀且在最浅的深度处从零开始线性增加时,峰值地动速度减小。这些结果有助于更好地预测由有潜在的危险断层所产生的强地面运动。
Three-dimensional finite difference method was used to simulate the strong ground motion caused by the rupture of shallow strike-slip faults. The rupture process is modeled by a crack pattern with a fixed rupture rate. Changes in the peak ground velocity image associated with fault location and source parameters (such as stress drop or fracture velocity) were also studied. Our findings indicate that these images are strongly influenced by the direction of fracture and the depth at the very upper part of the fault or asperities. When the fault breaks through the surface, the peak ground motional velocity and peak ground acceleration show a narrow, strong area of motion. When the fault is buried in the ground, the region parallel to the high peak of the fault where the component of the dynamic velocity is located has a distance from the fault trace that corresponds to the fault depth. On the other hand, the peak ground velocity perpendicular to the fault is the largest along the fault trace. The fault length (or asperity length) does not have much effect on the peak ground motion velocity. The effects of inhomogeneities related to stress drop and fracture velocity on strong ground motions are also studied. When the stress drop is not uniform and linearly increases from zero at the shallowest depth, the peak ground motional velocity decreases. These results help to better predict strong ground motion resulting from potentially dangerous faults.