Abstract: Since the Wenchuan earthquake,the seismic hazard of the northeastern segment of the Longmenshan Fault zone as well as the Hanzhong Basin has drawn more and more concerns. However,the essential data needed for further analysis on the seismic hazard in this region is scarce at present time,hence there is an urgent need for an in-depth study on the activities of faults around the basin. The faults around the Hanzhong Basin include five main faults,namely,the northern margin fault of Hanzhong Basin,the southern margin fault of Hanzhong Basin,the Qingchuan Fault,the Chaba-Lin'ansi Fault and the southern margin fault of Liangshan. Based on several detailed field investigations on the geometric distribution,movement nature and active ages of the five faults,and with consideration of previous work,our study shows that the late-Quaternary tectonic activity in the basin is relatively intense in west and weak in east. The west section of the north-margin fault of the Hanzhong Basin(east of Baohe)was active in early late Pleistocene,while its eastern section(west of Baohe)was active in middle Pleistocene. The south-margin fault of the basin was also active in middle Pleistocene. And the three faults in the southwest of the basin were all active in late Pleistocene. This activity pattern of high in the west and low in the east is also demonstrated by the difference in thickness of Quaternary system and the distribution of small earthquakes.

Key words: fault activity, late-Quaternary activity features, Hanzhong Basin

摘要： 汉中盆地周缘断裂包括汉中盆地北缘断裂、汉中盆地南缘断裂、青川断裂北段、茶坝-林庵寺断裂北段及梁山南缘断裂5支主要的断裂，通过对这几条断裂几何展布、运动性质及活动时代的野外调查，结合前人相关研究结果，揭示出汉中盆地周缘断裂晚第四纪活动性具有明显的东西差异，汉中盆地的控盆断裂，即汉中盆地北缘、南缘断裂的活动性较弱，为中更新世—晚更新世早期活动断裂，而盆地西侧的3条断裂均为晚更新世晚期活动断裂。该盆地晚第四纪以来活动性的西强东弱还表现在其第四纪沉积物厚度及小震分布的东西差异方面。

关键词: 断裂活动性, 晚第四纪构造特征, 汉中盆地