太原盆地田庄断裂几何特征及活动性分段研究

浅层地震勘探和联合钻孔剖面综合探测是研究城市隐伏活动断裂的重要方法之一,为查明太原盆地田庄活动断裂的空间展布、活动性质及活动时代等地质特征,综合浅层地震勘探、联合钻孔剖面、测年方法对断裂全段空间展布进行了精确定位,对断裂活动性进行了精细分析,给出了断裂几何特征及活动性分段研究结果.研究表明田庄断裂全长33.5 km,断裂全段均发育北支及南支断裂,主断裂为北支断裂,断面近似呈"Y"及"N"字形结构特征.根据断裂几何特征及活动性差异可将断裂划分为四段,其中断裂中段及中-东转折段最新活动时代为晚更新世晚期,最小上断点埋深分别为39.3 m及37.4 m,晚更新世以来断裂平均滑动速率为0.0283~0.0292 mm/a,最大滑动速率为0.0326~0.0415 mm/a;断裂东段最小上断点埋深为63.5 m,最新活动时代为中更新世晚期,中更新世晚期以来最大滑动速率为0.0134 mm/a,平均滑动速率为0.0092 mm/a;断裂西段最新活动时代为中更新世中期;断裂中段及中-东转折段活动性明显大于断裂西段及东段.首次基于联合钻孔剖面及浅层地震勘探方法查明了田庄断裂中段、中-东段及东段的活动性质,查明了田庄断裂全段的精确空间展布,首次提出了断裂的分段模式并进行了断裂活动性及活动速率研究,首次对断裂全段的浅部构造特征进行了精细研究,填补了田庄断裂全段基底以上地质结构特征研究的空白.研究结果可以为太原盆地城市防震减灾规划、震害预测、区域性地震安全评价提供重要的技术支撑.

Geometric characteristics and segmentation of activity of Tianzhuang fault in Taiyuan basin

Shallow seismic exploration and combined borehole profiling are one of the important methods to study buried active faults in cities.In order to find out the spatial distribution,nature and age of buried active faults in Tianzhuang,Taiyuan basin,shallow seismic exploration,combined borehole profiling and dating methods are used to synthesize the whole gap of the faults.The precise location of interfacial distribution and the detailed analysis of Quaternary activity of faults are carried out.The geometric characteristics of faults and the segmented research results of activity are given.The study shows that Tianzhuang fault is 33.5 km in length.The north and South Branch faults are developed in the whole segment of the fault.The North Branch faults are the main faults.The other sections are similar to the Y-shaped structure except for the section at the turning point of the West and Middle-East segments of the fault.According to the difference of geometric characteristics and activity of the faults,the faults can be divided into four segments.The latest active ages of the middle and Middle-East transition segments are late Late Pleistocene,with the minimum buried depth of the upper fault point being 39.3 m and 37.4 m,respectively.The average slip rate of the faults since Late Pleistocene is 0.0283~0.0292 mm/a,and the maximum slip rate is 0.0326~0.0415 mm/a.The minimum buried depth of the upper breakpoint in the eastern part of the fault is 63.5 m,and the latest active age is the late Middle Pleistocene.Since the late Middle Pleistocene,the maximum sliding rate is 0.0134 mm/a,and the average sliding rate is 0.0092 mm/a.;the latest active age in the western part of the fault is Mesopleistocene;the activity of the middle part of the fault and the Middle-Eastern transition section is obviously greater than that in the western and eastern part of the fault.For the first time,based on the joint drilling profile and shallow seismic exploration method,the activity of the middle section,Middle East section and east section of Tianzhuang fault has been found out,and the precise spatial distribution of the whole section of Tianzhuang fault has been found out.The segmentation mode of the fault has been put forward for the first time,and the study on the activity and activity rate of the fault has been carried out.For the first time,the detailed study on the shallow structural characteristics of the whole section of the fault has been carried out to fill the whole section of Tianzhuang fault.The research on the geological structure characteristics above the basement of the segment is blank.The research results can provide important technical support for urban earthquake prevention and disaster reduction planning,earthquake disaster prediction and regional seismic safety evaluation in Taiyuan basin.