虎牙断裂展布于岷山隆起的东边界一带,属于东昆仑走滑断裂向南东帚状撒开的尾部转换构造。通过高分辨率遥感解译、地质地貌和震害调查、微地貌测量、古地震探槽开挖及小震反演相结合的方法,对虎牙断裂的晚第四纪活动特征进行了研究。结果 表明1:20万地质图上所示虎牙断裂局部形成断错山脊、槽谷地貌等现象,属于断裂早期构造运动、岩性差异及外动力侵蚀共同作用的结果。断裂沿线第四纪断错微地貌不发育,地表未见其晚第四纪最新活动迹象。根据小震精定位及其反演的结果,结合野外地质调查结果,以雪山断裂和王朗为界,将虎牙断裂分为南段、中段和北段。断裂性质南北变化较大,自北向南表现为由隐伏走滑断裂向逆冲盲断裂逐渐转换。
The active Huya fault,belonging to the southeast tail structure of the east Kunlun fault,is distributed at east boundary of the Minshan uplift. To obtain its late quaternary activity,we use many methods,such as interpretation of high-resolution remote sensing image,geological landforms investigation,earthquake damage investigation of moderate-strong earthquakes,micro-geomorphic survey,excavation of paleo-earthquake trench,and inversion using small earthquakes. It is comprehensively analyzed that the Huya fault is the result of combined action due to pre quaternary tectonic movement of the fault,lithology difference,and external dynamic erosion. Firstly,there are no obvious signs of activity without faulted micro-landforms caused by active tectonics on the surface,and we consider that the active Huya fault may have not been ruptured to the surface.According to results of seismogenic fault inversion,combined with the latest geological research,the property of the Huya fault varies from northern buried strike slip to southern reverse thrust blind fault greatly. Taking the Xueshan fault and Wanglang as the boundary,it can be divided into three parts,such as the southern segment(south of Xueshan fault),the middle segment(Xueshang fault to Wanglang),the northern segment(north of Wanglang). The fault property changes vary much from north to south,showing hidden strike-slip characteristics in the north and thrust blind characteristics in the south.
