沧东断裂第四纪活动性探测结果

根据人工地震探测结果,分别在天津东丽区山岭子村北、大港区中塘村和宁河县北淮淀村布设了三条钻孔剖面,对沧东断裂开展了钻孔勘探工作。经微体古生物鉴定和地层年代测试,确定了各钻孔第一、第二、第三和第四海相层的位置。通过以海相层为标志层的地层对比并结合中塘村BZ1孔古地磁测试结果,对沧东断裂的活动性进行了分析研究。结果表明,沧东断裂晚更新世以来没有发现活动的迹象,其最新活动年代可能在中更新世。如果以海河断裂为界,从位于沧东断裂北部的北淮淀钻孔剖面和位于南部的中塘钻孔剖面的地层对比发现,沧东断裂北段、南段活动性差异不大。同时,已有的一些研究表明,海相层的观测可能对地震信息反映较好。除沧东断裂探测外,天津南、北断裂、海河断裂对21口钻孔进行了海相层鉴定,目前开展的蓟运河断裂探测也将对海相层位置进行确定,这些结果,对利用咸水层观测地震信息的层位选择有很大帮助。

Exploration Results of Quaternary Activities along the Cangdong Fault

Based on the results of artificial seismic exploration, three profiles of boreholes are arranged in the North Shanlingzi Village of Dongli District, Zhongtang Village of Dagang District, and Beihuaidian Village of Ninghe County. Through the identification of microfossils and the test of strata age, the locations of the marine strata of boreholes are obtained in this work. The activity of the Cangdong fault is analyzed and studied through strata contrast and the paleomagnetic test results of BZ1 bore in Zhongtang Village. The result indicates that the activity sign of the Cangdong fault has not been found since the Late Pleistocene and its latest active age might be in the Middle Pleistocene. The contrast result of the marine strata of the Beihuandian borehole profile in the northern part of the Cangdong fault and the Zhongtang borehole profile in the southern part shows that there is a little difference in activity between the southern and northern sections of the Cangdong fault, divided by the Haihe fault. In addition, previous research has shown that the marine strata observation may better reflect the information of earthquakes. Besides the Cangdong fault, the marine strata of 21 boreholes on the south Tianjin fault, north Tianjin fault, and Haihe fault were also identified, and the location of marine strata will also be determined in the current Jiyunhe fault detection.