四川龙泉山断裂带变形特征及其活动性初步研究

PRELIMINARY INVESTIGATION ON DEFORMATION CHARACTERISTICS AND ACTIVITY OF LONGQUANSHAN FAULT BELT IN SICHUAN

文中通过野外调查和地震反射剖面研究,获取了龙泉山断裂带的变形特征。龙泉山断裂带主逆冲断层位于龙泉山背斜的西翼,具有明显的分段性特征,北段与南段断层面倾向NW,断续分布;中段断层面倾向SE,形成典型的断层传播褶皱,并且断层已经沿背斜前翼膝折带的轴突破,形成贯通的突破断层。因此,中段构成了龙泉山断裂的主体。地貌对断裂活动性的响应表明龙泉山断裂早更新世—晚更新世有过一定的活动,晚更新世以来活动速率较低,且活动性具有从南向北逐渐减弱的趋势。

Based on the field work and seismic reflection profiling data,the paper investigates the deformation characteristics of the Longquanshan Fault zone. The main thrust fault of the Longquanshan Fault belt lies in the west of the Longquanshan anticline and has different properties from northeast to southwest. In the north segment and south segment of the Longquanshan Fault, the plane of fault dips to northwest and is uncontinuous,but in the middle segment,the plane of fault dips to southeast and is continuous. Therefore,the middle part of the fault is the main segment of the Longquanshan Fault. Structural geometries of the middle segment of the fault suggest classical fault-propagation folding and the fault ruptured along different axial directions. Historical earthquakes and geomorphological response to activity of the Longquanshan Fault indicate that the fault was active from the early Pleistocene to late Pleistocene, and its activity is weak since the late Pleistocene, and gradually decreases from south to north.