Abstract: The Yushu Batang Fault, which controls the development of Quaternary Batang Basin, Boluo tan Basin and Dangyong tan Basin along it, is a major branch fault of the Yushu segment within Ganzi-Yushu Fault system. Based on morphotectonic mapping, interpretation of remote sensing images, fault profile analysis, optically stimulated luminescence (OSL) and radiocarbon (14C) dating, it is found that a series of fluvial terraces and alluvial fans are systematically offset by the Yushu Batang Fault and this fault is a Holocene left-lateral strike-slip fault along with some reverse component. The time of the latest activity of this fault is after 2.72 ka. Average left-lateral slip rate of this fault is about 2.3?3.7 mm/a and vertical slip rate is about 0.2?0.6 mm/a since Late Pleistocene. The Yushu Batang Fault plays an important role in accommodating strike slip deformation in Yushu segment and partitioned about a third of the strike slip deformation within Yushu segment. This study provides insight into the reasons of why the slip rate of Yushu fault is relatively low compared with other segments within Ganzi-Yushu Fault system and these results are essential to the seismic hazard assessment in Yushu area.

Key words: Yushu Batang Fault, Ganzi-Yushu Fault, late Quaternary slip rate, seismic hazard assessment

摘要： 玉树巴塘断裂是甘孜-玉树断裂带玉树段的一条主要的分支断裂, 沿线发育第四纪巴塘盆地、波洛滩和当涌滩。通过遥感影像解译、野外构造地貌填图、断层剖面分析以及断错地貌面的光释光和14C年代测定, 发现该断裂沿线河流阶地、洪积扇断错明显, 是一条以左旋走滑为主, 兼具逆冲分量的全新世活动断裂。该断裂最新活动时代为全新世晚期, 距今2.72 ka。晚更新世晚期以来的左旋滑动速率为2.3~3.7 mm/a, 垂直滑动速率为0.2~0.6 mm/a, 该断裂在甘孜-玉树断裂带玉树段起着变形分解作用, 吸收了玉树段内约1/3的走滑变形。研究结果可以解释甘孜-玉树断裂带内玉树断裂走滑速率偏小的构造现象, 并为评价甘孜-玉树断裂带玉树段的地震危险性提供基础资料。

关键词: 玉树巴塘断裂, 甘孜-玉树断裂, 晚第四纪滑动速率, 地震危险性