Cenozoic Fault System and Tectonic Evolution of the Eastern Liaodong Bay Depression

Development characteristics of a fault system are an important manifestation of the structural evolution of the easternLiaodong Bay Depression in the Cenozoic period. Based on plenty of three dimensional seismic data, this paper describes the horizontaldecreased and sectional characteristics of fault systems in detail in the study area and analyzes the formation mechanism of the faultsystems. The result shows that the fault systems in the Paleocene and the Eocene mainly consist of NNE trending extensional faults.And the fault systems in the Oligocene have the strike-slip characteristics. The vicinity of main faults has significantly stress-increasedarea and stress-decreased area due to the strike-slip effect. The flower-liking structures andY-type structures can be observed in theseismic profiles. The secondary faults mostly consist of NEE trending en-echelon faults. The main faults and the secondary faults canform strike-slip duplex. In Neogene, the secondary faults are still manifested as NEE trending en-echelon faults and the fault systemshows characteristics of weak strik-slip. And conjugate shear fractures and antiform-negative flower structures began to appear in thisperiod. The study of the fault system illustrates the superimposition and transformation between extension tectonic systems andstrike-slip tectonic systems in the eastern Liaodong Bay Depression in the Cenozoic. Combined with dynamic evolutionary mechanism of the Bohai Bay Basin, the evolutionary stages of the eastern Liaodong Bay Depression can be divided into the weak strike-slip-strongextension period(Paleocene-Eocene), the weak extension-strong strike-slip period(Oligocene), and the weak compression-weakstrike-slip period(Neogene).