基于InSAR的广义海原断裂带中东段现今深部运动特征

Depth Present-Day Movement in the Mid-Eastern Segment of the Haiyuan Fault Zone Based on InSAR

以InSAR技术获取的高空间分辨率震间形变速率场作为约束,利用最速下降程序包(SDM,steepest descent method)反演了广义海原断裂带中东段(毛毛山断裂、老虎山断裂、狭义海原断裂)断层面上整体的震间滑动速率空间分布。结合区域历史强震和现今中小地震活动情况,分析讨论断层面上的现今应力积累状态和活动特征。结果表明,广义海原断裂带中东段以左旋走滑运动为主,由东至西各段的最大滑动速率依次为3.5mm/a、2.3mm/a及3.4mm/a,分别位于18~24km、18~21km及15~21km深处;毛毛山断裂闭锁深度约为9km,存在一定的应力积累,具备强震发生背景;老虎山断裂深部存在无震滑移,未来发生强震的可能性不大;狭义海原断裂活动存在分段差异,东、西两段断层滑移较明显,中段断层滑动速率较小(最大速率约为1.5mm/a),应在日常震情跟踪工作中予以关注。

In this paper,inter-seismic creep velocity distribution is inversed,based on the InSAR-derived deformation field,using the SDM（steepest descent method）code.Then,the present-day strain state of the fault is discussed based on the inter-seismic creep velocity distribution and the local seismicity.The results show that,firstly,the mid-eastern segment of the Haiyuan fault zone is dominated by left lateral strike slip,and the maximum creep rates are 3.5 mm/a,2.3 mm/a and 3.4 mm/a on depths of 18-24 km,18-21 km and 15-21 km,respectively,from east to west direction.Secondly,the locking depth of the Maomaoshan fault is approximately 9 km,showing accumulating stress,and has the potential for strong earthquakes.Thirdly,the Laohushan fault shows aseismic slip in depth,showing less potential with strong earthquakes.Fourthly,the Haiyuan fault shows different movement characteristics on different segments.The eastern and western segments of the Haiyuan fault show obviously afterslip.However,the central segment of the Haiyuan fault shows slight afterslip reaching to 1.5 mm/a,and should be monitored in routine works.