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报告了利用泡沫橡胶模拟浅部软弱层对走滑破裂引起的强地面运动影响的结果。走滑地震引起强地面运动的计算机模拟,有时与对断层浅部滑动特性的某些任意假设有关(如:断层面上部2km处的滑动固定为0)。断层滑动反演研究表明,走滑断层浅部的高频辐射通常低于断层深部。在多数情况下,(1)断层区上部几公里的断层可能较弱,不能维持地震高动能释放期间所要求的高水平的剪应力;(2)断层滑动可能具有不同的本构关系,例如,滑动强化。本文的目标是显示利用浅部软弱层进行物理模拟的结果,为假设断层浅部滑动引起长上升时间和高频脉冲降低提供物理基础。软弱区利用在泡沫橡胶模型中插入几英寸宽的软塑性层来模拟。软弱层长时间作用的强度比模型剩余部分低一个量级。瞬时速度强化的作用估计是动力滑动事件中滑动时的3倍。显示了沿走滑断层2km深的软弱区确实能降低浅部滑动的高频能量辐射,这种效果可以由在长得多的上升时间滑动突发时增加一较小幅值的短上升时间脉冲来描述。对15cm的软弱区,平均脉冲幅值降低了约4/10。对于20cm情形,降低了约2/10,30cm时降低了约1/10。根据这些结果可以看出,软弱层越厚,短上升时间加速度脉冲通过软弱层到达表层就越困难。软弱层速度强化特性进一步降低滑动运动和增长上升时间。在模拟研究中,如果已知断层浅部是软弱层或未储存大的剪应力,这些结果支持走滑断层浅部的高频辐射减少的结论。
The results of using foam rubber to simulate the effects of shallow weak layers on strong ground motion caused by strike-slip cracking were reported. Computer simulations of strong ground motions caused by strike-slip earthquakes are sometimes associated with some arbitrary assumptions on the slip characteristics of shallow faults (eg, slip fixation at 2 km above the fault plane is zero). The fault slip inversion shows that the high frequency radiation in the shallow part of the strike-slip fault is usually lower than that in the fault. In most cases, (1) faults of a few kilometers in the upper part of the fault zone may be weak and the high level of shear stress required during high kinetic energy release of the earthquakes may not be maintained; (2) fault slip may have different constitutive relationships, for example, Slide to strengthen. The objective of this paper is to show the results of physical simulations using shallow weak layers, providing the physical basis for assuming long-rise time and high-frequency pulse reduction in shallow faults. The weakened zone is modeled by inserting a few inches wide of soft plastic layer into the foam rubber model. The strength of the weak layer over a long period of time is one order of magnitude lower than the rest of the model. The effect of instantaneous speed enhancement is estimated to be 3 times as much as sliding during a dynamic slip event. Shows that the weak zone 2 km deep along the strike-slip fault can indeed reduce the high-frequency energy radiation of the shallow slip by adding a small amplitude short rise time pulse when sliding the burst at a much longer rise time To describe. For the 15cm weak zone, the average pulse amplitude is reduced by about 4/10. For the 20 cm case, a reduction of about 1/10 at 30 cm was achieved. From these results, it can be seen that the thicker the weak layer, the more difficult it is for the short rise time acceleration pulse to reach the surface through the weak layer. Soft layer velocity enhancement features further reduce the sliding motion and increase the rise time. In modeling studies, these results support the conclusion that HF in the shallow part of the strike-slip faulting decreases if it is known that the shallow part of the fault is a weak layer or large shear stress is not stored.