【摘要】 郯庐断裂带中南段与西太平洋板块俯冲以及华北克拉通破坏密切相关，研究其深部结构对于了解郯庐断裂带构造演化过程、强震的孕震机制具有重要意义.本文利用密集台阵波形资料，采用接收函数H-κ叠加方法获得郯庐断裂带中南段的地壳厚度和泊松比.结果显示，郯庐断裂带中南段的地壳厚度分布以庐江和新沂为分段点呈现出与地质构造相关的南北向分段特征：南段的断裂带西侧的地壳厚度比东侧厚约5 km,中段的断裂带两侧厚度差异减小至约3 km,而北段则表现为断裂带下方隆起特征.郯庐断裂带沿线的地壳泊松比较高，推测是地幔物质的热侵蚀和化学侵蚀所致.根据艾里地壳均衡理论，南段地壳厚度与地表高程相关，基本符合艾里地壳均衡模型；而中段两侧地表高程基本相同，两侧地壳厚度差异表明不符合艾里地壳均衡模型，可能与断裂带西侧的华北克拉通岩石圈比东侧扬子克拉通岩石圈具有更高密度有关，高密度岩石圈产生向下“拖拽力”导致莫霍面相对理论值偏深；北段的莫霍面也偏深，与中段断裂带西侧情况类似，该区域基本位于华北克拉通块体.在郯城地震破裂范围内，存在莫霍面的不平滑过渡、活动块体的边界带以及断裂的分叉与交汇这三类结构特征.在上述结构特征的区域应力更集中，从而孕育产生了1668年郯城8.5级地震.更多还原

【Abstract】 The middle-southern segment of the Tan-Lu fault zone(TLFZ) is related to the subduction of the west Pacific plate and the destruction of the North China Craton. The study of deep structure in the TLFZ is of great significance for understanding the tectonic evolution of the TLFZ and the seismogenic mechanism of strong earthquakes. In this study, we use data from dense seismic arrays to estimate the crustal thickness and Poisson′s ratio beneath the middle-southern segment of the TLFZ by H-κ stacking method. The results show that the distribution of crustal thickness can be divided into three segments with Lujiang and Xinyi as the subsection points. The segmentation characteristics in the north-south direction are consistent with that of the geological structure. In the southern segment, the crustal thickness on the west side of the TLFZ is about 5 km greater than that on the east side. In the middle segment, the crustal thickness difference between the two sides of the TLFZ decreases to about 3 km. In the northern segment, the crustal thickness is characterized by “thick-thin-thick” and the Moho interface is uplifted beneath the TLFZ. The high Poisson′s ratio beneath the TLFZ is presumed to be the result of thermal and chemical erosion caused by mantle material. According to the Airy isostasy theory, we concluded that:(1) In the southern segment, the crustal thickness is related to the elevation, which largely conforms to the Airy isostasy model.(2) In the middle segment, the elevations on both sides of the TLFZ are close but the crustal thicknesses are quite different, which indicates that the deep structure does not conform to the Airy isostasy model, which may be related to the higher density lithosphere of the North China Craton on the west side of the TLFZ than that of the Yangtze Craton on the east side, for high-density lithosphere can produce a downward “drag force” which leads to a deeper Moho interface than that by thoery.(3) In the northern segment, the Moho interface is deeper than that based on the Airy isostasy model. The deep structure of this area is similar to that of the west side of TLFZ in the middle segment, which belongs to the North China Craton. Within the rupture zone of the M 8.5 Tancheng earthquake, there are three types of structural features: uneven transition of Moho interface, the boundary of active blocks, bifurcation and intersection of faults. These structural features are beneficial for stress concentration, thus leading to the occurrence of the M 8.5 Tancheng earthquake in 1668.更多还原