天津汉沽断裂准确位置及活动性的综合探测研究

Comprehensive survey and investigation on the exact spatial location and activity of the Hangu fault in Tianjin

天津汉沽隐伏断裂属于滨海平原区隐伏断裂。本文采用化探、浅层地震勘探和联合钻孔剖面探测等方法,并结合年代样品测试对汉沽断裂进行了综合探测研究,首次查明了汉沽断裂的准确空间位置和晚第四纪活动性。探测结果表明,汉沽隐伏断裂最新上断点埋深25.8m,断距为2.15m。结合光释光年代样品测试结果,推断其最新活动时代为49.3ka^65ka BP,属晚更新世中期活动断裂。由于该断层是与主断层倾向相反的次级断层,可能并不是震源断层错动在地表的直接反映,同时汉沽断裂晚更新世早期以来的平均滑动速率为0.063mm/a,明显低于海河断裂东段晚更新世以来0.141mm/a的平均滑动速率,这都表明汉沽隐伏断裂的活动强度并不是很大,应是一具有中等活动强度的活动断裂。

The Hangu buried fault in Tianjin belongs to the buried fault of coastal plain area. The paper used methods of geochemical exploration,shallow seismic exploration,drilling exploration and sample age to survey and research on the Hangu buried fault. This is the first identification of the exact spatial location and the Late Quaternary activity of the Hangu buried fault. The results showed that the depth of the latest upper break point of Hangu buried fault is 25. 8m,fault throw is 2. 15 m. Combining with the test results of the optically stimulated luminescence dating sample,we found that the latest active age is between 49. 3ka - 65 ka BP,which belongs to the late Pleistocene active fault. But the fault is secondary fault,with a tendency opposite to the main fault. The fault may not be the direct reaction of the earthquake source fault on the surface,and the slip rate of Hangu fault since the early Late Pleistocene is 0. 063 mm / a,significantly lower than the eastern section of the Haihe fault which has an average slip rate of 0. 141 mm / a since the Late Pleistocene. All this indicates that the activity strength of Hangu buried fault is not strong,an active fault of moderate activity level with the maximum potential earthquake with MS6. 5.