天津海河隐伏断裂的晚第四纪活动特征研究

CHARACTERISTICS OF LATE QUATERNARY ACTIVITY OF THE HAIHE BURIED FAULT IN TIANJIN MUNICIPALITY

在海河隐伏断裂精确定位的基础上 ,文中利用天津地区晚第四纪地层中的 4个海相地层作为标志层 ,通过地质钻孔勘探、微体古生物鉴定、地层对比及年代学测定和研究 ,获得了海河断裂的晚第四纪活动特征。研究表明 ,海河断裂在天津市区段的上断点埋深为 2 1m ,对应的最新活动时代为晚更新世晚期至全新世早、中期 ,塘沽区段的上断点埋深为 16 4m ,最新活动时代已进入了全新世早、中期 ;天津市区段在晚更新世晚期 (36 2 90aBP)以来 ,垂直运动速度为 0 2 4 8mm/a ,塘沽区段全新世(72 0 0aBP)以来的平均垂直运动速率为 0 333mm/a。这表明海河断裂塘沽区段 (东段 )的活动性明显高于市区段 (西段 )。

On the basis of precise locating of the Haihe buried fault, the characteristics of late Quaternary activity of the fault was identified through drilling, identification of microfossils, stratigraphic correlation and chronological dating, by taking 4 marine strata of late Quaternary ages in Tianjin area as key horizon. The result indicates that the upper breaking point of the Haihe Fault in Tianjin downtown area is buried 21m below ground surface, and the corresponding latest movement of the fault had continued through the late stage of late Pleistocene to the early stage of Holocene. On the Tanggu segment of the fault, however, the upper breaking point is buried 16.4m deep, and its latest active period was in the early and middle stage of Holocene. Therefore, the average vertical movement rate on Tianjin downtown segment since the late stage of late Pleistocene (36290a BP) can be estimated as 0.248mm/yr, and that on the Tanggu segment since the middle stage of Holocene (7 200a BP) may reach 0.333mm/yr. This may indicate that the activity of the Haihe Fault on Tanggu segment (eastern segment) is obviously stronger than that on the Tianjin downtown segment (western segment).