喜马拉雅主山前逆冲断裂现今构造运动状态与应力演化规律研究

The most active fault of Himalayan subduction is Himalayan Main Frontal Thrust, with high degree of locking, large thrust rate and part of which are lack of strong earthquakes for hundreds years. Moreover, there is densely population on the peripheral portion area, so it is significant to study the stress evolution and modern stress state along Himalayan Main Frontal Thrust. Based on high resolution 3D crustal movement velocity field obtained from InSAR，GPS data and leveling observations, we could simulate slip rate, locking depth and tectonic stress accumulation rate on different segments and depth of the fault. With the slip models of historical earthquakes, we will analyze co-seismic and post-seismic Coulomb stress changes along Himalayan Main Frontal Thrust. On this basis, we will further discuss the stress accumulation on different segments and depth of Himalayan Main Frontal Thrust caused by co-seismic, post-seismic and inter-seismic effect and their relationship with the regional seismic activity. Stress evolution along Himalayan Main Frontal Thrust could provide clues for better understanding of regional tectonic deformation mode, regional seismogenic mechanism and earthquake triggering mode.

喜马拉雅主山前逆冲断裂是喜马拉雅俯冲系统中最为活跃的断裂带，闭锁程度高，逆冲速率大，部分断裂段长期缺乏强震活动，且周边不乏人口稠密区域，研究喜马拉雅主山前逆冲断裂应力演化规律和现今应力状态具有重要意义．本课题将融合喜马拉雅主山前逆冲断裂周边密集的InSAR数据、GPS测站和水准测量等大地测量资料，获取研究区高分辨率三维地壳运动速度场；综合现有地质学、大地测量学资料，将喜马拉雅主山前逆冲断裂作为一个完整系统建立粘弹性断层位错模型；以有限元方法模拟并深入研究断裂带不同分段，不同深度的滑动速率、闭锁程度以及构造应力积累速率；基于应力触发理论与粘弹性地壳分层模型，获取历史强震在断裂带不同深度、不同部位引起的库仑应力变化及其演化规律；结合构造应力积累，探索同震、震后、震间效应引起累积库仑应力随时间的演化过程及其与历史强震活动的关系，揭示喜马拉雅地区动力学机制及中强震孕育与触发模式．

喜马拉雅主山前逆冲断裂是喜马拉雅俯冲系统中最为活跃的断裂带，闭锁程度高，逆冲速率大，部分断裂段长期缺乏强震活动，且周边部分区域人口稠密，研究喜马拉雅主山前逆冲断裂应力演化规律和现今应力状态具有重要意义．本课题利用喜马拉雅主山前逆冲断裂周边密集的InSAR数据、GPS测站和水准测量等大地测量资料，获取了研究区高分辨率三维地壳运动速度场；综合现有多学科资料，将喜马拉雅主山前逆冲断裂作为一个完整系统建立粘弹性断层位错模型；以有限元方法模拟并深入研究了断裂带不同分段，不同深度的滑动速率、闭锁程度以及构造应力积累速率；基于应力触发理论与粘弹性地壳分层模型，获取了历史强震在断裂带不同深度、不同部位引起的库仑应力变化及其演化规律；结合构造应力积累，获取了喜马拉雅主山前逆冲断裂同震、震后、震间效应引起累积库仑应力随时间的演化过程及其与历史强震活动的关系．