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郯庐断裂带是中国东部板内一条规模最大的强构造变形带与地震活动断裂带，其断裂结构与历史地震活动性具明显的分段活动性。本文通过沿郯庐断裂带中南段的历史地震活动性、精定位背景地震活动性与震源机制解分析，讨论了断裂带的深部几何结构与现今活动习性。现今地震活动在中段主要沿1668年郯城MS 8地震破裂带线性分布，线性条带在泗洪—诸城间延伸约340 km长,为1668年地震长期缓慢衰减的余震序列活动。大震地表破裂遗迹与精定位地震分布都揭示出郯庐断裂带中段的两条全新世活动断裂昌邑—大店断裂与安丘—莒县断裂以右阶斜列的形式共同参与了1668年郯城MS 8地震破裂。精定位震源剖面刻画出两条断裂结构面呈高角度相背而倾，其中昌邑—大店断裂倾向SE，安丘—莒县断裂倾向NW，两条断裂在深部没有合并汇聚。余震活动所代表的1668年地震震源破裂带是郯庐断裂带中现今尚未闭锁的安全段落，对应于高b值段。而未发生破裂的安丘以北段，小震活动不活跃，b值低，现今可能已成为应力积累的闭锁段。震源机制解揭示的断裂应力状态在中段以NE向主压应力为主，表现为右旋走滑活动性质，且存在少量正断分量，南段转为以NEE至近EW向为主，存在少量的逆冲分量。在中段与南段的转折处宿迁—嘉山段，主压应力方向垂直断裂带走向呈NWW向，反映出局部以挤压为主的应力特征，其中泗洪—嘉山段也是历史地震未破裂段，现今小震活动不活跃，因此该段可能更易于应力积累。精定位小震活动在郯庐断裂与北西向断裂相交汇处聚集，反映出北西向断裂的新活动性，以及郯庐断裂带现今的逆冲作用。在断裂带南端，精定位背景地震活动沿与其相交汇的襄樊—广济断裂带东段呈北西向线性分布，表明了该段的现今活动性，震源机制解显示出其左旋走滑的活动性质。
The Tan-Lu fault zone is the largest strong tectonic deformation zone and seismic activity fault zone in the eastern China plate. Its fault structure and historical seismicity have obvious segmental activities. Based on the historical seismic activity along the middle and south sections of the Tan-Lu fault zone, the seismic background of the fine-setting background and the focal mechanism analysis, the deep geometry of the fault zone and the current activity habits are discussed. Nowadays, the seismic activity is linearly distributed along the rupture zone of Tancheng MS8 earthquake in 1668 in the middle segment. The linear stripe extends about 340 km long between Sihong and Zhucheng. It is a long-term aftershock sequence activity of slow attenuation of the 1668 earthquake. The rupture of the epicontinental earthquakes and the distribution of the precise earthquakes all reveal two active faults in the central part of the Tanlu fault zone: the Changyi-Dadian fault and the Anqiu-Juxian fault were co-involved in 1668 Tancheng MS 8 earthquake ruptured. The finely defined seismic source profiles depict that the two fault structures face upside-down and tilt at high angles. The Chang-Dadian fault tendency SE and the Anqiu-Juxian fault tendency NW are not merged in the deep. The aftershock activity represented by the 1668 earthquake source rupture zone is a safe passage in the Tan-Lu fault zone that has not yet been closed and corresponds to a high b-value segment. The northern section of Anqiu, where rupture did not occur, is characterized by an insignificant small-amplitude seismic activity and low b-value, which may now be a block of stress accumulation. In the middle section, the fracture stress state revealed by the focal mechanism solution is dominated by the NE-directed compressive stress, showing a dextral strike-slip activity with a small amount of normal-fault component, with the south section changing from NEE to near-EW direction with a small amount of Thrust component. In Suqian-Jiashan section at the turning point of the middle section and the southern section, the vertical fracture direction in the direction of principal compressive stress shows NWW direction, which reflects the stress characteristics of partial compression. Among them, Sihong-Jiashan section is also the unbroken section of historical earthquake, Small earthquakes are not active today, so the section may be more prone to stress buildup. The finely-defined small earthquakes gathered at the junction of the Tanlu fault and the NW strike fault, reflecting the new activity of the NW strike fault and the current thrusting action of the Tan-Lu fault zone. At the southern tip of the fault zone, the seismic activity along the finely defined background is linearly distributed to the northwest along the east segment of the Xiangfan-Guangji fault that intersects with it, indicating the present activity of this segment. The focal mechanism solutions show the activity of the left-lateral strike-slip .