田庄断裂中段活动性研究

Activity of the middle part of Tianzhuang fault

田庄断裂是太原盆地内由2条断层组成的隐伏断裂带,前人研究认为田庄断裂错断了上更新统下部地层,判定该断裂的活动时代为晚更新世早期.我们通过浅层地震勘探获得:田庄断裂带主断裂可分辨的上断点埋深约为53～58 m,垂直断距约3～4 m.跨断层钻孔联合剖面揭示:在58～60 m地层错断量在1. 4 m左右,74～90 m地层整体错约1 m,最近的一次地震错动量加大约1/2,说明地震活动性呈现加强趋势;从断层两层的沉积速率来看,上盘晚更新世晚期以来沉积速率为3. 8mm/a,下盘近全新世以来沉积速率为2. 2 mm/a,全新世以来上盘比下盘沉积速率快近一倍.综合测年和地层对比,田庄断裂主断裂错断了上更新统上部地层,最新活动时代为晚更新世晚期.

The Taiyuan Basin is located in the middle of the Cenozoic Rift Valley in Shanxi Province,and is heading northnortheast. The west,north,and east sides of the Taiyuan Basin are surrounded by mountains. The Tianzhuang fault is a concealed fault zone consisting of two faults in the Taiyuan basin. The north fault is the main fault,the south fault is the main fault associated fault,and the primary and secondary faults are normal faults. Previous studies have suggested that the Tianzhuang fault has broken the upper strata of the Upper Pleistocene and determined that The active age of the break was early in the late Pleistocene. We obtained through shallow seismic exploration： The distinguishable upper break point of the main fault of the Tianzhuang fault zone is about 53 ～ 58 m in depth,and the vertical fault distance is about 3 ～ 4 m. Cross-fault drilling combined profile reveals： in the 58 ～ 60 m strata, the dislocation amount is about 1. 4 meters,the overall strata of 74 ～ 90 meters is about 1 m apart,and the recent earthquake displacement amount is about 1/2,indicating that seismic activity is enhanced;from the deposition rate of the fault two layers,the deposition rate was 3. 8 mm/a since the late late Pleistocene in the upper plate,the deposition rate was 2. 2 mm/a in the lower plate since the Near Holocene,and the upper plate has been compared with the lower plate since the Holocene. The deposition rate is nearly doubled.Based on the results of comprehensive dating and stratigraphic comparison,the main fault of the Tianzhuang fault distorted the Upper Pleistocene upper strata. The latest active age was late Late Pleistocene. It is of great significance to guide the planning and construction of urban areas in Taiyuan City by clarifying the age and activity capacity of Tianzhuang faults.