Study On Strike-slip Deformation Under Extensional System

The main boundary fault(fault No.1)in the Yinggehai basin is an extension of the Red River Fault to sea area,and the 3D seismic data do not support the traditional understanding of this fault.Under the guidance of a generalized fault theory,this paper analyzes the tectonic background of the Yinggehai basin and dissects the 3D seismic data of the working area in detail,it is concluded that fault No.1 in the Yinggehai basin is an inclined slip normal fault(passive strike-slip fault)formed under the extensional system under the previous tectonic condition.Taking this as the starting point,in order to further study the strike-slip deformation under the extensional system,the conceptual model and the analogue modeling of the target model under the extensional system were designed and studied in detail.The following conclusions are obtained:(1)The basement preexisting structure controls the overall pattern of the basin,and the tectonic evolution of the fault is controlled by the strike,dip angle of the preexisting structure and the influence of the regional extensional direction and extensional amount.(2)The difference between the extension direction and the preexisting structure,the characteristics of the passive strike-slip fault displacement and the sedimentary and filling modes controlled by it vary greatly in different regions.(3)The fault No.1 in the Yinggehai Basin is a passive strike-slip fault formed on the basis of the preexisting structure(NE-SW direction rifting)and then subjected to north-south extension(Oligocene-Miocene).Combined with structural physical simulation experiments,it is found that the fault No.1 in the Yinggehai Basin not only has significant strike-slip displacement,but also has a certain amount of dip-slip displacement,and that the boundary faults have different strike-slip displacements in different sections;the geometric characteristics of the fault No.1 on the profile and its control effect on the basin structure show great differences on different profiles,which is consistent with the basic characteristics of the passive strike-slip fault proposed in this paper.(4)Considering comprehensively the results of structural physics simulation experiments and literature research results of strike-slip faults,combined with the dynamic mechanism,a new classification scheme for strike-slip faults is proposed,and the new classification scheme is used to briefly analyze the famous strike-slip faults at home and abroad.By analyzing the structural characteristics and genetic mechanism of the main boundary fault(fault No.1)in the Yinggehai basin,it is of certain theoretical significance to further analyze the structural evolution and the later oil and gas exploration in the Yinggehai basin.