郯庐断裂带肥东段第四纪活动特征及最新活动时代

Quaternary activity characteristics and latest active age of the Feidong segment of the Tan-Lu fault zone

郯庐断裂带作为中国东部一条巨型断裂带,同时也是一条重要的地震活动带,其第四纪活动特征及地震活动性仍然存在争议。郯庐断裂带肥东段详细的野外地质调查表明,该段存在大量活断层,主要发育在合肥盆地东缘与肥东杂岩接触带内,呈北东—北北东向展布,以逆右行平移活动为主,是早期盆缘正断层复活的产物。根据活断层和擦痕数据反演得到肥东段活断层形成时的主压应力方向为北东东—南西西向挤压,与该地区当今主压应力方向一致。对采集的3个断层泥样品进行ESR年代学测定,得到其年龄分别为510±72 ka,589±118 ka和940±94 ka,指示郯庐断裂带肥东段最新活动时代为早更新世晚期至中更新世,与该段近代无强震及北东向小震聚集现象相符。活断层动力学背景可能受控于太平洋板块向北西西向的俯冲及印度板块与欧亚板块碰撞造成的向东挤出的远程效应的共同作用。

The Tan-Lu fault zone(TLFZ),as a huge fault zone in eastern China,is also an important seismically active belt.Its Quaternary activity characteristics and seismicity are still controversial.Detailed field geological survey of the Feidong segment of the TLFZ shows that there are a large number of active faults in this area,which are mainly developed in the contact zone between the eastern margin of the Hefei Basin and the Feidong complex.The active faults occurred in NE-NNE trending,with nature of the reverse dextral displacement,which were renewed by the pre-exist normal fault in the basin margin.Inversion of the measured faults and scratches data indicates that active faults in the Feidong segment were formed under ENE-WSW compression.ESR dating of the collected three fault gouge samples show that the ages are 510±72 ka,589±118 ka,and 940±94 ka,respectively,indicating that the latest active age of the Feidong section of the Tan-Lu fault zone is the late Early Pleistocene to Middle Pleistocene,which is consistent with the absence of strong earthquakes and NE-trending cluster of small earthquakes in this segment in modern times.The dynamic background of active faults may be controlled by the WNW subduction of the Pacific Plate and the remote effect of eastward extrusion caused by the collision between the Indian Plate and the Eurasian Plate.