2013年MS7.0芦山地震的动力学破裂过程及其影响因素

2013年4月20日在四川芦山发生了M S7.0地震,震源运动学反演结果给出了此次地震的破裂过程和同震滑动分布.为了更好地理解造成芦山地震破裂过程的力学原因,本文综合野外地质调查、余震定位、深地震反射剖面等结果,构建芦山地震铲型断层模型,以震源运动学反演结果为约束,将震源参数与震源附近的构造应力场结合,建立断层面上滑动量和牵引力的时空分布关系,通过试错法给定震源动力学计算参数模拟芦山地震破裂传播的可能情况,进而分析讨论不同动力学计算参数对芦山地震破裂过程和同震滑动分布的影响.结果显示,初始应力是决定断层是否发生错动的关键;临界滑动弱化位移D c对破裂滑动速率有着很大的影响;成核区半径和初始应力主要影响破裂成核的快慢;局部不均匀破裂强度主要影响破裂行为和断层最终滑动量分布.利用边界积分方程法可以有效计算芦山地震铲型断层模型的动力学破裂过程,再现此次地震的主要特征.通过探究动力学参数对破裂过程影响,可解释运动学反演结果所揭示的破裂特征的力学原因,对于深入了解地震震源过程的物理本质和预测未来可能发生的地震的主要特征有着重要的参考意义.

Simulation of rupture process and its influence factors of the 2013 MS7.0 Lushan earthquake

The M_S7.0 earthquake occurred on April 20, 2013 in Lushan, Sichuan province. The kinematic inversion on the source of this earthquake revealed the rupture process and co-seismic slip distribution of the earthquake. Based on the results of field geological survey, aftershock location and deep seismic reflection section, a listric fault model for the Lushan earthquake is constructed. In order to better understand the mechanical causes of the rupture process of the Lushan earthquake, we combine the source parameters with the tectonic stress field near the source and establish the temporal and spatial distribution relationship between the slip and traction on the fault plane. We simulate the rupture process of the Lushan earthquake by using the trial-and-error method with the given dynamic parameters based on the source kinematic inversion results and then discuss the influence of different dynamic parameters on the rupture process and co-seismic slip distribution of the Lushan earthquake. The results show that the initial stress is the key to decide whether the fault ruptures or not. The critical slip weakening displacement D_c has a great influence on the slip rate. The radius of nucleation zone and the initial stress of nucleation zone mainly affect the rate of nucleation. The local inhomogeneous fracture strength has a major effect on the fracture behavior and final slip distribution. In a word, the boundary integral equation method can effectively calculate the dynamic rupture process of the listric fault model of the Lushan earthquake and reproduce the main characteristics of the earthquake. The mechanical causes of fracture characteristics revealed by kinematic inversion results can be well explained by exploring the influence of dynamic parameters on the rupture process, which is important to understand the physical nature of seismic source process and to predict the main characteristics of the possible future earthquakes.