郯庐断裂带合肥段五河—合肥断裂构造特征

五河—合肥断裂是郯庐断裂带的西边界断裂，该断裂穿过合肥市城区，是1条规模较大、切割较深的隐伏活动断裂.为了研究该断裂的浅部结构特征、空间展布以及断裂活动性，我们利用2015年在合肥盆地完成的深地震反射剖面数据，采用初至波层析成像方法得到了郯庐断裂带合肥段的浅层P波速度结构和构造形态；考虑到仅根据速度结构剖面还难以确定断裂的准确位置、断层上断点埋深、断层的近地表构造组合样式等特征，研究中跨五河—合肥断裂还完成了2条高分辨率的浅层地震反射剖面.研究结果表明：郯庐断裂带合肥段是一个由多条主干断裂构成的复杂构造带，近地表速度结构表现为凹隆相间的构造特征，且沉积盖层厚度明显受到郯庐断裂带分支断裂的影响和控制.五河—合肥断裂在P波速度结构剖面表现为高速和低速区的分界，对断裂两侧的地层沉积具有重要的控制作用，该断裂向下错断了盆地基底，向上错断了埋深21~35 m的中更新统下部地层，其最新活动时代为中更新世早期.研究结果不仅为进一步认识五河—合肥断裂浅部构造形态提供了地震学依据，还可为该区断裂两侧的城镇规划和建设中避让活动断层提供基础资料.

Structural characteristics of the Wuhe-Hefei fault on the Hefei segment of the Tanlu fault zone

The Wuhe-Hefei fault is the west branch of the Tanlu fault zone, which is a large-scale, deep-cutting buried active feature, passing through the city of Hefei. In order to probe the shallow structural characteristics, shape and activity of this fault, we applied a first-break wave imaging method to explore shallow P-wave velocity structure in this area based on deep seismic reflection profile data acquired in 2015. Considering it is difficult to determine the accurate position of the fault, the upper-breakpoint depths and the near-surface tectonic patterns of faults only by the velocity structure profile, we also completed two shallow high-resolution seismic profiles across the target fracture.#br#The results show that the Hefei segment of Tanlu fault zone is a complicated structure consisting of multiple major faults. The near-surface velocity structure exhibits alternating depressions and uplifts. Thickness of the sedimentary cover is obviously influenced and controlled by the branches of the Tanlu fault zone. The Wuhe-Hefei fault itself is a boundary between high-velocity and low-velocity on the P-wave velocity structures, which has an important control on sediments of either side of the fault. This fault cuts down the Hefei basin basement, and offsets the overlying lower part of the Middle Pleistocene strata at depths 21~35 km, implying its latest activity in the early Middle Pleistocene.#br#The results of this study can provide not only new seismological evidence for further analysis of the shallow structural feature of the Wuhe-Hefei fault, but also the basic information for the city planning and construction on either side to avoid active faults in this area.