太原盆地田庄断裂活动性分段及地震危险性分析研究

为厘定太原盆地中部潜在的发震断层情况,对田庄断裂实施了浅层地震勘探,结果表明:1)田庄断裂可分为3个区段,各区段内均发育北、南支断裂,其中北支断裂为主断裂;2)除断裂西端及中-东段转折部位断面呈近似“N”形结构外,其余断面均呈“Y”形;3)西段断裂带宽度最小,东段断裂带宽度最大。利用年代学测试方法结合钻孔剖面确定断裂的活动年代及滑动速率,断裂中段的活动年代为晚更新世晚期,上断点最小埋深为39.3 m,晚更新世以来最大断距为2.9 m,最大滑动速率为0.0415 mm/a;断裂西段及东段的活动年代为中更新世,中-东段转折部位上断点最小埋深为37.4 m,晚更新世以来最大断距为2.7 m,最大滑动速率为0.0461 mm/a。基于浅层地震揭示的基岩破裂长度,采用地震矩方法对田庄断裂进行地震危险性概率分析,确定断裂的最大潜在震级及发震概率。

Segmentation and Seismic Risk Analysis of Tianzhuang Fault in Taiyuan Basin

In order to identify potential seismogenic faults in the central part of Taiyuan basin, we carry out shallow seismic exploration of Tianzhuang fault. The results show that: 1) Tianzhuang fault can be divided into three sections, in which the north branch faults are the main faults. 2) Except for the western end of the fault and the turning section of the middle-eastern segment, the other sections are similar to the “Y” structure. 3) The fracture bandwidth of the eastern segment is the largest and the smallest. The active ages and slip rates of the faults are determined by borehole profiles and chronological methods. The active ages of the middle part of the fault are late Late Pleistocene, the minimum buried depth of the upper fault point is 39.3 m, the maximum fault distance since late Pleistocene is 2.9 m, and the maximum slip rate is 0.041 5 mm/a. The active ages of the western and eastern segments are middle Pleistocene, and the minimum buried depth of the upper fault point at the turning point of the middle-eastern segment is 37.4 m. Since the late Pleistocene, the maximum fault distance is 2.7 m and the maximum slip rate is 0.046 1 mm/a. Based on the fracture length of bedrock revealed by shallow earthquake, seismic moment method is used to analyze the seismic risk probability of Tianzhuang fault, and the maximum potential magnitude and seismogenic probability of the fault are determined.