中条山北麓断裂解州段晚更新世滑动速率研究

Study on Late Pleistocene Sliding Rate of Haizhou Section of North Zhongtiaoshan Faults

中条山北麓断裂是鄂尔多斯块体东南缘运城盆地南缘主边界断裂,控制运城盆地的构造演化过程。滑动速率是活动断裂定量研究最重要的参数之一,也是断层活动方式和强度的直接反映,该段滑动速率值对运城盆地的地震危险性评估、中长期预测有着重要意义。以中条山北麓断裂解州段为重点,利用高分辨率遥感影像解译、地质地貌调查、无人机测量、断层剖面分析以及地层年代测定等方法,对该断裂的晚第四纪活动习性、地貌面变形以及活动速率开展详细研究,获得以下三点认识:①中条山北麓断裂解州段存在一系列与主断层相平行的次级断裂,越靠近盆地内部,断层发育时间越晚,活动性越强;②晚更新世以来盐池一带主要发育三期洪积扇,最早一期洪积扇废弃年龄为14.1~15.7 ka,地貌面上的断层陡坎平均高度为10.2~11.7 m;断层的平均垂直滑动速率为0.65~0.83 mm/a;③小李村南(15.7±2.5)ka以来断裂平均垂直滑动速率为0.45~0.62 mm/a;(107.4±18.6)ka以来平均垂直滑动速率约为0.1 mm/a,晚更新世断裂的活动性有逐渐增强的趋势。

North Zhongtiaoshan Fault is the main boundary fault of the southern margin of Yuncheng basin at the southeastern margin of Ordos block, which controls the tectonic evolution of Yuncheng basin. Sliding rate is one of the most important parameters for quantitative study of active faults, and it is also a direct reflection of the mode and intensity of fault activity. The value of sliding rate in this section is of great significance for seismic risk assessment and medium-and long-term prediction of Yuncheng Basin. Focusing on the Haizhou section of the north piedmont fault in Zhongtiaoshan Mountains, by using the methods of high resolution remote sensing influence interpretation, geological and geomorphological investigation, UAV survey, fault profile analysis and stratigraphic dating, we studied the Late Quaternary activity habits, geomorphological surface deformation and activity rate of the fault in detail. Three main points were obtained, ① there are a series of secondary faults parallel to the main fault in Haizhou section of North Zhongtiaoshan Faults, The closer to the basin, the later the faults developing and the stronger their activity;② there are three main stages of alluvial fans in Yanchi area since the late Pleistocene, and the abandoned age of the first stage of alluvial fans is 14.1~15.7 ka, the average cutting height being 10.2~11.7 m;and the average vertical slip rate of faults is 0.65~0.83 mm/a;③ the average vertical slip rate of faults in south Xiaolicun is 0.45~0.62 mm/a since(15.7±2.5)ka;the average vertical slip rate since(107.4±18.6)ka is about 0.1 mm/a, and the activity of faults in Late Pleistocene is gradually increasing.