郯庐断裂带安徽段活断层特征与成因

详细的野外地质调查表明,郯庐断裂带安徽段活断层广泛存在,自北向南分别沿着嘉山盆地的东、西边界、合肥盆地东界与大别造山带东界分布。走向上自北向南由北北东向转为北东向,倾向上与早期盆缘正断层一致。这些活断层以逆右行平移活动为主,显示了逆冲分量随着断层倾角变小而增大的现象。依据一系列活断层擦痕实测数据的反演,指示它们活动时的应力状态为北东东-南西西向挤压,与现代应力状态一致。从多种现象综合分析,本文认为郯庐断裂带安徽段活断层的最新活动时代应为中更新世,从而该段没有强震记录或小震群集现象。本次工作表明,区内活断层主体上是早期盆缘正断层直接复活成因。由于其第四纪期间有限的累计垂直位移分量,并没有改变白垩-古近纪盆地发育阶段的地貌格局。

Features and genesis of active faults in the Anhui segment of the Tan-Lu fault zone

Our detailed filed investigation demonstrates the wide-spread presence of active faults in the Anhui segment of the Tan-Lu fault zone. They occur along the eastern and western boundary of the Jiashan Basin and the eastern boundaries of the Hefei Basin and Dabie orogenic belt. The active faults strike from NNE-SSW to NE-SW from north and south, and show similar dips to previous normal faults at the basin boundaries. Kinematics of the active faults dominated by reverse dextral displacement, but showing increased in reverse component with reduction in dip angles. Inversion of a series of measured fault-slip data indicates NEE-SWW compression for activity of the active faults, which is consistent with present stress field. Many phenomena suggest Middle Pleistocene for the most recent time of the activity in the Anhui segment of the Tan-Lu fault zone, which is consistent with the absence of strong earthquakes and weak earthquake concentration in the fault zone. We propose that the active faults originated from direct reactivity of the previous basin boundary normal faults. The limited magnitudes of accumulated vertical displacement along the active faults led to no change in topographic patterns formed during the basin development of Cretaceous to Paleogene.