甘孜-玉树断裂带东南段晚第四纪活动性研究

RESEARCH ON LATE QUATERNARY ACTIVITY OF THE SOUTHEASTERN SEGMENT OF GANZI-YUSHU FAULT ZONE

以甘孜-玉树断裂带东南段的地质地貌为研究对象,在遥感解译的基础上,通过对典型地区的详细野外调查和探槽研究对该段晚第四纪活动性进行研究。在断裂沿线的生康乡、仁果乡、错阿乡、日阿乡进行了断错地貌分析和晚第四纪滑动速率计算,生康区的水平滑动速率为(7.6±0.5)mm/a,垂直滑动速率为(1.1±0.1)mm/a;仁果区的水平滑动速率为(8.0±0.3)mm/a,垂直滑动速率为(1.1±0.1)mm/a;错阿区的水平滑动速率为(10.3±0.4)mm/a;日阿区的水平滑动速率为(10.8±0.8)mm/a,垂直滑动速率为(1.1±0.1)mm/a。在仁果乡和错阿乡进行了探槽研究,两处探槽都揭示了多次古地震事件,虽然揭露的断层构造样式有所不同,但总体上都是以走滑为主兼有一定的逆冲分量。综合古地震事件和滑动速率分析表明,甘孜-玉树断裂带东南段晚第四纪尤其是全新世以来活动剧烈。

Taking tectonic geomorphology of southeastern Ganzi-Yushu Fault zone as the research object, and based on remote sensing interpretation, the paper investigates the late Quaternary activity of the southeastern segment of Ganzi-Yushu Fault zone through trenching and detailed field investigation on several typical sites. We analyze the landscapes and calculate the late Quaternary slip rates along the fault zone at the sites in Shengkang township, Renguo township, Cuoa township, and Ria township, respectively. The horizontal and vertical slip rates are （7.6＋ 0. 5 ） mm/a and （ 1. 1 ＋ 0. 1 ） mm/a at Shengkang township, （8.0_＋0. 3 ） mm/a and （ 1.1-＋0. 1 ） mm/a at Renguo township. And horizontal slip rate of Cuoa township is （10.3_＋0.4） mm/a. The horizontal and vertical slip rates of Ria township are（10.8_＋0.8 ） mm/a and （ 1.1_＋0.1 ） mm/a, respectively. Both trenches at Renguo township and Cuoa township have revealed several paleoearthquake events. Though there are some differences in fault tectonic styles revealed between the two trenches, the fault motion on this segment is of strike-slip with a certain amount of thrust component on the whole. Associated with the analysis of paleoearthquake events and slip rate, it is found that the southeastern Ganzi-Yushu Fault zone is subject to intensive activity since late Quaternary,especially since Holocene.