动力学走滑断层地震动方向性效应谱元法模拟

Simulation of the directivity effect of dynamic strike-slip fault based on spectral element method

采用动力学震源模型,运用谱元法模拟走滑断层单、双侧破裂模式的地面运动,分析模拟2种模式下地震动的方向性效应和脉冲效应,并对比分析2种模式下断层破裂速度、滑移量与滑移速率的异同。研究结果表明:单、双侧破裂模式下的FN分量PGV均表现出明显的方向性效应,而FP分量的PGV方向性效应不明显,且单侧破裂较双侧破裂的地震动方向性效应强;单侧破裂较双侧破裂更易产生脉冲效应,脉冲效应随断层距的增加而减小,表现为脉冲峰值V p与脉冲周期T p的减小;脉冲效应与方向性效应的出现使地震动的低频含量提高,且这种效应也将随断层距的增加而减小;单、双侧破裂模式断层的破裂速度与滑移量无明显差异,而最大滑移速率表现出方向性效应,且单侧破裂较双侧破裂明显。

The dynamic source model and spectral element method are used to simulate the ground motion of unilateral and bilateral rupture modes of strike-slip faults in this paper.The directivity effect and pulse effect of ground motion under the two modes are simulated and analyzed,and the similarities and differences of fault rupture speed,slip distance and slip rate under the two modes are compared and analyzed.The results show that:the PGV of FN component shows obvious directivity effect under both unilateral and bilateral rupture modes,while the directivity effect of FP components is not obvious,and the directivity effect of unilateral rupture is stronger than that of bilateral rupture.Unilateral rupture is more likely to produce pulse effect than bilateral rupture.,the pulse effect decreases with the increase of fault rupture distance,which is characterized by the decrease of pulse peak V p and pulse period T p.The emergence of pulse effect and directivity effect increases the low-frequency content of ground motion,and this effect will also decrease with the increase of fault distance.There is no significant difference between the fault rupture speed and slip distance of the unilateral and bilateral rupture modes,but the maximum slip rate shows directivity effect,and the unilateral rupture is more obvious than the bilateral rupture.