Differential tectonic deformation in the northern Qiyueshan Fault, eastern Sichuan Basin

The geometrical and kinematic characteristics and fault evolution history of the Qiyueshan Fault were analyzed systematically using seismic and geological data. The profile morphology of the Qiyueshan Fault from north to south shows in turn a “Y”, “zigzag” and spade shape. The exposed fault inclination changes from northwest to southeast. The Qiyueshan Fault is characterized by a sectional structure. The structural pattern of the western periphery of the fault, from north to south, changes from “hidden thrust and fault-slip fold of the Wushan-Tuxiang segment” to “fault-spread and slip fold of the Tuxiang-Zhongxian segment”, to “basement thrust-fault-spread fold of the Zhongxian-Jiaoshi segment”, to “thrust fold of the Jiaoshi-Nanchuan segment”. The eastern periphery of the fault is characterized by thrust structural deformation. The Qiyueshan Fault was formed in the Early Yanshanian stage, and then underwent extrusion in the middle Yanshanian Movement and extension in the late Yanshanian Movement. The middle section of the fault is the most deformed. Different structural deformations lead to the obvious difference of oil and gas preservation conditions on both sides of the fault.