基于大地测量与地质数据约束的红河断裂带滑移速率和闭锁特征反演研究

The Red River Fault (RRF) in Yunnan is a large-scale strike-slip fault system experienced long period evolution, and tectonic activity has significant segment features. The historical strong earthquakes on RRF ruptured frequently its northern section. However, the central and southern sections of the fault have not produced a great earthquake in historic times. Today there are still a large controversy about the recent strength of actual activities and seismic hazard situation on RRF. In this project, the high-resolution deformation velocity field near and far RRF have been obtained from the geodetic techniques of GPS and InSAR. A new combined-inversion 3D block models have been constructed that is constrained by the GPS velocities, InSAR velocities and the geology-based fault slip rates. Based on 3D block model and least squares method, the geometry and kinematic parameters such as locking depth, deep fracture surface geometry exhibition and recent three-dimensional movement rate were inversed. On this basis, to analyze interseismic deformation and fault creep deformation process, to study present tectonic deformation pattern, strain accumulation and locking status. The relations were determined between the fault active and regional tectonic strain. The potential earthquake hazard were estimated. The scientific issue was answered about 'tectonic activity is weak, has lost the status and role of the southwest boundary of the Sichuan-Yunnan block or currently in a strong lock state, still has the possibility of large earthquakes occurred on the central and southern sections of RRF', and to provide decision support for regional seismic hazard assessment.

红河断裂带是我国云南境内一条经历长期演化的大型断裂，构造活动具有显著的分段特征，其中，北段历史强震频繁，而中－南段鲜有地震发生。关于该断裂现今的实际活动强度和地震危险性状况，目前仍有较大的争议。本项目拟对红断裂带远近场GPS和InSAR联合观测获取高分辨率的形变矢量速度场，以创建的GPS、InSAR速度矢量和地质走滑速率约束的三维形变块体模型，采用最小二乘法，反演确定断裂带的闭锁深度、深部断裂面几何展布及三维运动速率等参数，分析震间形变及断层蠕动形变过程，研究断裂带的现今构造运动模式、应变积累程度、闭锁状况，确定断层活动与区域构造应变关系，评价潜在的地震危险性。从根本上回答"现今的红河断裂活动微弱，是已丧失川滇块体西南边界的地位和作用，还是目前处于强闭锁状态，仍具有发生大震的可能性"这一科学问题。

红河断裂带是我国云南境内一条经历长期演化的大型断裂，构造活动具有显著的分段特征，其中，北段历史强震频繁，而中－南段鲜有地震发生。关于该断裂现今的实际活动强度和地震危险性状况，目前仍有较大的争议。本项目通过对红断裂带远近场GPS和InSAR联合观测获取高分辨率的形变矢量速度场，以创建的GPS、InSAR速度矢量和地质走滑速率约束的三维形变块体模型，采用最小二乘法和模拟退火算法，反演确定断裂带的闭锁深度、深部断裂面几何展布及三维运动速率等参数，分析震间形变及断层蠕动形变过程，研究断裂带的现今构造运动模式、应变积累程度、闭锁状况，确定断层活动与区域构造应变关系，评价潜在的地震危险性。结果表明：红河断裂带北段右旋走滑速率为4.76±0.78mm/a，闭锁深度约为10.9km；中段右旋走滑速率为3.24±0.56mm/a，闭锁深度约为11.5km；南段右旋走滑速率为2.83±0.34mm/a， 闭锁深度约为12.6km。红河断裂带整体闭锁程度不高，从地表至地下1.25km处闭锁系数约为0.846，1.25~6.25km处的闭锁系数约为0.846~0.337，6.25~11.25km处的闭锁系数约为0.337~0.185，从12.15~15km处逐渐转变为完全蠕滑，到15km处闭锁系数为0。红河断裂带北段与中段拉张应变特征明显，南段挤压应变特征明显，北段拉张应变值为(20~40)×10-9/a，南段挤压应变值为(30~50)×10-9/a；中段最大剪应变积累较弱，量值为(0~30)×10-9/a，北段、南段最大剪应变积累较强，量值为(40~80)×10-9/a，北段和南段元阳地区出现最大剪应变高值区，地震危险性较大。红河断裂带两侧存在显著的地质结构差异使得不同区段构造运动强度呈现明显的分区性，北段活动强烈且受程海断裂影响较大，中段与无量山断裂和南华—楚雄—建水断裂在上地壳与之发生归并，共同控制区域构造运动，南段受小江断裂影响，小江断裂弧以西呈顺时针旋转运动，以东呈逆时针旋转运动。解答了“现今的红河断裂活动微弱，是已丧失川滇块体西南边界的地位和作用，还是目前处于强闭锁状态，仍具有发生大震的可能性”这一科学问题。