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.