阿尔金断裂东北段敦煌阳关断裂晚第四纪活动性及其强震危险性影响分析

Late Quaternary Slip along Yangguan Fault at Northeastern Section of Altyn Tagh Fault and Implications for Seismic Risk

阿尔金断裂系东北段阳关断裂的晚第四纪活动性与强震危险性关系到敦煌地区及相关文物古迹的防震减灾问题.基于高分辨率卫星影像对阳关断裂几何展布特征进行解译,采用差分GPS、无人机航空摄影测量方法、古地震探槽方法以及OSL测年方法对两个研究点进行了详细研究,对其定量活动参数进行了初步限定.结果显示,阳关断裂东段运动形式主要表现为挤压逆冲,最新的一次地震事件可能发生在距今43.5~12.1 ka之间,表明阳关断裂东段至少在晚更新世以来有过活动,并且具有发生Mw 6.6强震的潜能及危险性.如果发生类似强度的地震,敦煌主城区的烈度至少在Ⅵ以上,阳关土遗址地区则会达到Ⅸ.因此,阳关断裂应该是该区防震减灾重点关注的发震断层之一.

The Yangguan Fault is located on northwestern section of the Altyn Tagh Fault,which is a large strike slip fault and seismotectonic in Northeast Tibet Plateau,which poses potential seismic hazard to city development and culture relics in Dunhuang area.In this study it focuses on characterizing activity of the Yangguan Fault,using high resolution satellite imagery to map faults in space.At two study sites,it made detailed investigation by methods of difference GPS,aerial photogrammetry with unmanned aerial vehicle,paleoseismical trench and Optically Stimulated Luminescence dating.The preliminary results are that the Yangguan Fault is a thrust fault trending NEE with high dipping angle;its latest event likely occurred between 43.5 ka and 12.1 ka.The results imply that the eastern section of the Yangguan Fault ruptured at least during Late Pleistocene.It is proposed that the eastern section rupture will cause an earthquake of Mw6.6,shaking the nearby area strongly,and the seismic intensity in the Dunhuang downtown will be more thanⅥ,reaching up toⅨat Yangguan relic site.Therefore,the Yangguan Fault is an important seismic fault in West Hexi Corridor.This study provides critical data for seismic prevention and disaster mitigation for city development and culture relic protection in Dunhuang area.