郯庐断裂带宿迁北晚第四纪以来新活动的微观证据

Microscopic evidence of new activities since late Quaternary in northern Suqian of Tancheng-Lujiang fault zone

为探索断裂晚第四纪以来新活动的微观依据,我们以郯庐断裂带宿迁北马窑开挖探槽断层新活动断错物质为主要研究对象,结合前人工作对比分析,识别编录晚第四纪以来变形和史前地震事件遗迹,分析其活动习性,定向采集断错物质,进行显微构造分析.发现一系列丰富复杂的微观变形组构和组合.镜下多处可见张压显微变形共处、变形带被切割等二次变形现象,显示该段至少有过2次活动,早期表现为拉张,晚期显示为挤压.宏、微观构造分析结合年代分析表明,晚第四纪以来,该断层段先行引张,然后发生强烈的挤压逆冲活动,均可能伴随强烈的史前地震活动,最新活动处晚更新世末期,年代分别为距今约为1.5万年和1.2万年.

For the micro-basis for exploring new activities since the late Quaternary fault,we take the fault dislocation material with new activity as the main study object,in trench of Mayao,northern Suqian of Tancheg-Luinang fault zone,combining the comparative analysis of previous works,identify the catalog of Late Quaternary prehistoric earthquakes and deformation event relic,analysis the active behavior,redirect collecting the fault substances,making microstructure analysis. A rich and compiles series of microscopic deformation textures and combinations are discovered. Coexistence of multiple visible tensile and pressure micro-deformation are found under the microscopic,cutting deformation belt,such as secondary deformation,displays the segment at least 2 times activity,early tension, late show as compress. Combined with chronological analysis and macro-micro structural analysis shows that since the late Pleistocene,the fault segment was extension at first,and then strong activity with compress thrust had been taken. That is,2 times larger prehistoric earthquakes had been taken in the segment at least since late Quaternary,the latest activity from late Pleistocene to early Holocene, time for about 15000 years and 12000 years respectively.