2016年3月2日苏门答腊M_S7.8地震同震位移和应力场数值模拟研究  

Numerical study on the co-seismic deformation and stress changes of the M_S7.8 Sumatra earthquake,March 2,2016

作　　者：邓园浩 程惠红[1] 张怀[1] 瞿武林 张贝[1] 石耀霖[1] 

机构地区：[1]中国科学院大学中国科学院计算地球动力学重点实验室,北京100049

出　　处：《地球物理学报》2017年第1期174-186,共13页Chinese Journal of Geophysics

基　　金：国家自然青年科学基金项目(41404078);国家自然科学重大项目(41590860)联合资助

摘　　要：苏门答腊地区发育多条左旋走滑性质断层,地震活动活跃.2006年3月2日该区西南海域发生了M_S7.8大地震.大地震的发生常常会引发区域位移场和应力场及周围断层应力状态发生变化.本文建立全球PREM有限元地球模型,据已有的断层滑动模型计算了此次苏门答腊地震引发的同震位移和应力及库仑应力变化,并进一步讨论了此次地震对周围断层的影响以及区域构造应力场对库仑应力变化计算的影响.初步结果表明此次苏门答腊M_S7.8地震造成较大的南北向水平位移且集中在探测者破裂区(Investigator Fracture Zone),最大水平位移量约6.74 m,断层倾角接近垂直,下盘向北运动而上盘向南,进一步表明Ms7.8地震为典型的左旋走滑为主的地震,发生海啸的可能性较低;库仑应力变化达MPa量级的区域集中在震中,但近场大部分余震分布在库仑应力减小区域,有效摩擦系数变化和区域构造应力场的耦合作用可能是其原因;利用改进的库仑应力变化计算方法和最优破裂方向计算得出的结果显示库仑应力触发理论可较好地解释余震分布.Seismic activities are extremely frequent in Sumatra, attributed to well-developed multiple left-lateral strike-slip faults. An Ms7.8 earthquake, occurred on March 2, 2016 in Sumatra, caused co-seismic deformation and stress changes both in near and far fields as well as the surrounding faults. According to the present fault slip model, a global PREM finite element earth model is constructed to calculate the co-seismic displacements and Coulomb failure stress changes, as well as the impact on surrounding faults induced by this Sumatra earthquake. Then we discuss the influence of the regional tectonic stress field on the Coulomb failure stress change. The preliminary results show that： 1） horizontal displacements in south-north direction focus on the Investigator Fracture Zone, with the largest displacement of 6.74 m; 2） the footwall moves northwards, while the hanging wall in an opposite direction. The results indicate that the seismic fault of MsT. 8 earthquake is a typical left-lateral strike-slip fault and the risk of tsunami is low. The magnitude of Coulomb failure stress change is up to MPa order, which focuses on the vicinity of epicenter. However, most of aftershocks located in the regions with negative Coulomb failure stress, which may be attributed to the uncertainties of effective friction coefficient and regional tectonic stress field. Based on the improved method of calculating Coulomb failure stress change and the principle of optimal fractured direction, the new results indicate that the distribution of aftershocks could be well explained by the Coulomb failure stress triggering theory.

关 键 词：苏门答腊地震 同震效应 库仑应力 有限元模拟 

分 类 号：P542[天文地球—构造地质学] P315[天文地球—地质学]