河西走廊西端文殊山南缘断裂新活动特征

New activity characteristics of the southern Wenshushan fault in the western Hexi Corridor

摘要:

文殊山南缘断裂为新发现的位于河西走廊西端嘉峪关—文殊山隆起带南侧的一条活动断裂,研究其活动特征对完善区域构造图像、认识地区地震危险性具有重要意义。文章根据遥感影像解译、野外地质调查、航空摄影测量,结合年代学测试,对断裂进行综合研究。结果表明,文殊山南缘断裂长约25 km,断裂总体走向为NW向,倾向NE。根据断错及未断错地貌测年,确定该断裂最新一次地震活动的时间在(0.8±0.1) ka与(1 887~1 725) cal a BP之间。利用高精度数字高程模型数据,获得断层陡坎高度,结合相应的地貌年代,估算断裂垂直滑动速率在0.2~0.25 mm/a。根据地震震级与破裂长度、位移量经验公式,估算文殊山南缘断裂潜在发震能力在6.8级左右,此震级下可能对邻近的乡镇、嘉峪关市区有较大的影响。

Abstract:

The southern Wenshushan fault, located on the southern side of the Jiayuguan-Wenshushan uplift in the western Hexi Corridor, is a newly discovered active fault. Studying its activity characteristics is crucial for enhancing the regional tectonic understanding and assessing seismic risk in the area. This study conducts a comprehensive study of the fault based on remote sensing image interpretation, field geological surveys, aerial photogrammetry, and chronological dating. The results indicate that the southern Wenshushan fault extends approximately 25 km to the northwest and dips to the NE. Dating of faulted and unfaulted landforms indicates that the latest seismic activity on the southern Wenshushan fault occurred between (0.8±0.1) ka and (1 887—1 725) cal a BP. Using high-precision digital elevation model data, the heights of the fault scarps were measured. Combined with the corresponding geological age, the vertical slip rate of the fault was estimated to be between 0.2 and 0.25 mm/a. According to the empirical relationship between earthquake magnitude, rupture length, and displacement, the potential seismic magnitude of the southern Wenshushan fault is estimated to be around 6.8. This magnitude could significantly impact nearby towns and the Jiayuguan urban area.