郯庐断裂带中段第四纪活动及其分段特征

Quaternary Activity and Segmentation Behavior of the Middle Portion of the Tan-Lu Fault Zone

郯庐断裂带是中国东部一条岩石圈尺度的构造不连续带。位于江苏和山东境内的郯庐断裂带中段 ,在新构造运动时期强烈右旋走滑复活 ,形成地貌形迹显著的走滑活动断裂带。笔者在断层活动形迹的野外调查和观测的基础上 ,结合TM遥感影象特征解译和地震震源机制解资料 ,分析了郯庐断裂中段第四纪活动的分段行为特征。位于嘉山 潍坊之间的郯庐断裂带中段可以进一步划分为 3段 ,北段安丘 茅埠亚段 ,中段汪湖 宿迁亚段 ,南段宿迁 嘉山亚段 ,这三段可能分别是独立的地震破裂段。观测表明 ,新构造变形主要集中在宿迁以北的中、北段 ,是历史强震的发生段 ,而南段变形相对较弱。嘉山以南安徽境内郯庐断裂新构造变形更弱。郯庐断裂带新构造走滑变形的走向分段行为是华北地区不同块体新构造运动位移调节的结果。

The Tan-Lu fault zone is one of the major lithospheric discontinuities in eastern China. The middle portion of this fault zone in Shandong and Jiangsu provinces was subjected to strong right-lateral reactivation during Neotectonic era, forming a conspicuous transpressional strike-slip boundary in North China.Based on field observations together with TM imagery interpretation and focal mechanism solutions of earthquakes, this paper describes Quaternary active features and segmentation behavior of the Tan-Lu fault zone. It is pointed out that the middle portion of the Tan-Lu fault zone can be divided into three main segments, i.e., the Anqiu-Maobu segment, the Wanghu-Suqian segment and the Suqian-Jiashan segment in southward succession, and each of them might be ruptured independently. Quaternary strike-slip faulting is prevalent along the central and northern segments, north of Suqian, where two strong historical earthquakes once occurred, whereas the faulting weakens along the southern segment in Jiangsu and Anhui provinces. This along-strike segmentation behavior of the Neotectonic activity of the Tan-Lu fault zone accommodated book-shelf motion of blocks in North China.