关键词: 东昆仑活动断裂带, 全新世滑动速率, 断错地貌, 河流阶地, 断层位错

Abstract: The Eastern Kunlun Fault zone in northern Tibetan Plateau is one of the largest active fault zones in the world,demonstrated by a composite surface rupture zone of more than 700km long. However,the quantitative studies of the fault zone have remained scarce until recently mostly due to the difficulties of carrying out field investigation in this area. In this paper,we analyze offset values along the fault and their relevant TL and 14 C dating samples collected during our field investigation,from which we estimate the Holocene horizontal slip rates and earthquake recurrence intervals along the fault segment between the Toson Hu Lake and Kendingna (east Maqen). It is found that roughly along the Maji peak of the A'nyemaqen Mountains,the eastern Kunlun Fault section can be subdivided geometrically into two discontinuous segments:the Huashixia segment (from the Toson Hu Lake to the Maji Peak) and the Maqen segments (from the east of the Maji Peak to east of Kendingna). These two segments have significantly different Holocene slip rates and paleo-earthquake activities,with increased activity on the Huashixia segment. The Holocene horizontal sinistral slip rate on the Huashixia segment is estimated to be 11.5?1.1mm/a from five offset locations,while that of Maqen segment to be 7.0?0.6mm/a from study of four offset measurements. Furthermore,the vertical differential rising rates caused by the fault are estimated to be 2 1?0 3mm/a for the Huashixia segment since 4ka BP,and about 0.55mm/a for the Maqen segment since 10ka BP. These significant differences in the slip rates between the two segments indicate strongly some behavioral changes for the eastern Kunlun Fault striding over the Maji peak of the A'nyemaqen Mountains; meanwhile,the relatively large vertical differential rising rates may support a rapid Holocene rising of this region.

Key words: Kunlun Fault, Holocene slip rate, river terrace, fault displacement