Structural Characteristics and Evolution Mechanism of Paleogene Faults in the Central Dongying Depression, Bohai Bay Basin

Abstract This study used the growth index, fault activity rate and fault distance burial depth curve methods to analyze the characteristics of fault activity in the central area of Dongying depression. Using typical fault evolution and dynamic analysis to study the stages of fault evolution in the area, and using physical simulation experiments to study the mechanism and evolution process of fault formation. According to the results, the faults in the study area can be classified into four types. The Shicun fault and the pre-existing faults in the basin developed in the Paleogene Kongdian to Es4 period. Es3x and Es3z stages were characterized by strong extensional fault activities. The effect of strike-slip transformation from the Es3s to Es1 period was strengthened. The extensional fault continued to be active in Dongying period, and the strike-slip fault was basically stopped. The study area has been in the depression stage since Neogene. The physical simulation experiments show that the northern He 125 fault system is a fault combination composed of a main fault and broom-shaped branches formed by normal fault activities in the early stages and dextral strike slip processes in the late periods. The central en echelon fault system is a fault combination composed of three R fractures inherited the NE-SW basement fault and regulated by the later dextral strike-slip activities. The southern Wangjiagang fault system is a complex fault combination composed of Wangjiagang structure (P fracture) and Bamianhe structure (R fracture) developed from the Tanlu concealed branch strike-slip fault. This paper provided important reference for further research on the tectonic evolution and hydrocarbon accumulation in Dongying depression.