The Research Of Oblique Slip-Normal Fault In The South Of Jiyang Depression Since Late Jurassic

Oblique-slip fault is widespread,and the research area exits a series of oblique-slip faults because of the complexity of the stress field.We research the oblique-slip normal faults in the south of Jiyang Depression,and this research makes an important impact in the exploration and development of mineral resources and the prevention of geological disasters.We study the geometric and kinematic features of oblique-slip normal faults in the south of Jiyang Depression since the late Jurassic by researching the field geological surveys and geophysical logging data.Analyze the dynamics mechanism of oblique-slip normal fault in the research area since the late Jurassic according to the plate movement,the upwelling of geothermal substance and the evolution of Tan-Lu fault zone.Restore the balanced cross-section and compute the tendency slip and strike slip of faults.Analyze the correspondence of faults and stress field according to the stress field.We find mostly oblique slip faults are caused by pre-existing fault reactivation.Linshang fault in Huimin depression grows a series of en echelon normal faults by the pre-existing fault reactivation.Chennan fault in Dongying depression experience the diversification of stress field and its character is changing.Fault is the weak interface of earth crust,its growth is a progressive development process.The growth and reactivation of faults conform the Coulomb Criterion——the external force must overcome the rupture surface cohesion and friction.By analyzing the influencing factors of the fault resurrection,we find four genetic models of the oblique-slip normal fault: general shear,oblique stretch of normal fault,slip stretch of normal fault,stretch of strike-slip faults.Late Jurassic-Early Cretaceous,eastern China was in back-arc extension because of the subduction of Izanagi plate.At the same time,Tan-Lu fault sinistral strike-slip,which make the research area was in stretch-slip stress field.Late Cretaceous,the subduction of Pacificplate made research area in east-western Compressive stress field.Cenozoic,the research area was in stretch-slip stress field because of the subduction of Pacific plate and the remote effect of Indian plate subduction.Quaternary,as the activity of plate subduction and Tan-Lu fault zone was gradually decreased,the faults in research area died down step by step.