Abstract: The Xiaojiang fault is the southern portion of the Kangding fault zone, which is a noticeable active fault in southwest China and plays an important role in the left-lateral extrusion of the Tibetan Plateau. We determined average slip rates of the Xiaojiang fault, on the basis of offset landforms that were precisely mapped and dated by radiocarbon or thermoluminescence methods. The Xiaojiang fault consists of two subparallel fault strands in its middle segment; the average left-lateral slip rates on the west and east strands were determined to be 7.0～9.0mm/yr and 6.0～7.5mm/yr, respectively. Thus, the total slip rate on the Xiaojiang fault amounts to 13.0～16.5mm/yr. This value is approximately equal to that on the Xianshuihe fault, the northern part of the Kangding fault zone, and about twice as high as that on the Anninghe and Zemuhe faults, the middle part of the Kangding fault zone. Our results suggest that there must be other active faults that accommodate the missing slip in the middle of the Kangding fault zone; the most probable candidate may be the Puxionghe-Butou fault zone located several ten kilometers to the east of the middle segment.

Key words: Active fault, Slip rate, Xiaojiang fault, Southeastern Tibet

摘要： 位于中国西南的小江(Xiaojiang)断裂带作为康定(Kangding)断裂带的南段,在青藏块体向SE方向挤出的过程中起着重要的作用.根据断错地貌以及这些断错地貌14C年代或热释光年代,推算了小江断裂带第四纪晚期的左旋走滑速率.小江断裂带可以分为3段,其中段由平行的两条断层组成.西支断层和东支断层的左旋走滑速率分别为7.0～9.0mm/yr和6.0～7.5mm/yr.简单相加,就可以推算出小江(Xiaojiang)断裂带总的左旋走滑速率为13.0～16.5mm/yr,与康定断裂带北段的鲜水河(Xianshuihe)断层的走滑速率大致相当,约等于康定(Kangding)断裂带中段的安宁河(Anninghe)断层及则木河(Zemuhe)断层的两倍.这个结果可能暗示了在康定断裂带中段,可能存在着其他断层以解消另外一半的滑动速率.最有可能的断层是位于康定断裂带中段以东几十公里的普雄河-布拖(Puxionghe-Butuo)断层.

关键词: 活动断层, 滑动速率, 小江断裂带, 青藏高原东南