玉树断裂带左旋走滑活动标志及其几何学 与运动学特征

玉树断裂带位于甘孜-玉树断裂带北西段,是一条总体呈NWW向展布的左旋走滑活动断裂带.沿断裂带发育错断水系与冲沟、拉分盆地、地震地表破裂与断裂破碎带等一系列反映玉树断裂带左旋走滑活动的典型地质-地貌标志.在室内遥感解译的基础上,结合最新的野外实地调查成果,对沿玉树断裂带上反映其左旋走滑活动的地质-地貌标志进行了总结,并对断裂带的几何学与运动学特征进行了综合分析.结果表明,玉树断裂带总长约150km,总体走向120～130°,自西向东可划分为呈左阶雁列分布的陇蒙达-结隆段、结隆-结古段和结古-查那扣段3段.沿该断裂带发育的串珠状拉分断陷盆地规模的大小反映出玉树断裂带自西向东拉张效应逐渐减弱、挤压效应逐渐增强的特点.玉树2010年7.1级地震的宏观震中处于晚第四纪活动性最为显著的中段,而仪器震中恰好处于该断裂带的不连续部位,进一步证明雁列走滑活动断裂带上的不连续部位通常是强震活动的初始破裂区域.

The geomorphologic and geological marks of the active left-lateral strike-slip fault and the characteristics of geometry and kinematics along the Yushu fault zone in southeastern Tibet

Located in the northwestern part of Garze-Yushu fault zone, the Yushu fault zone is a NW-trending active left-lateral strike-slip fault. There are a series of indications reflecting the left-lateral strike-slip fault activities such as offset streams and gullies, pull-apart basin distributed along the fault zone. Based on the interpretation of satellite images and the detailed field survey and measurement work along Yushu fault zone, the authors systematically summarized the indicators of the active left-lateral strike-slip fault, the morphological characteristics and the kinematics marks. The results show that the Yushu fault zone strikes 120~130°in general, with clear segmentation in space. It can be divided into three left-stepped segments from west to east, i.e., Longmengda-Jielong segment, Jielong-Jiegu segment and Jiegu-chanakou segment. The scales of pull-apart basins on the fault zone indicate the characteristics of the weakening of the tension effect and the gradual increasing of the pushing effect from west to east along the Yushu fault zone. The epicenter of Yushu 2010 earthquake lay in the discontinuous part of the fault zone, suggesting that the discontinuous zone of en echelon strike-slip faults is usually a high-risk area of seismic activity.