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The Control Interaction of Extension and Strike-Slip on the Structure Characteristics in the Liaodong Bay Depression

Abstract

The Liaodong Bay depression is an secondary tectonic unit of Bohai Bay basin. It is controlled and affected by subduction of Pacific plate, upwelling of deep mantle, remote effects of the India-Asia continental collision and strike-slip of Tanlu fault zone. Interaction of extension and strike-slip control tectonic evolution and deposition of Liaodong Bay depression, which leads to various structural deformation and complex process of hydrocarbon accumulation.Based on abundant 3D seismic data, displacement along the strike and trend of the main fault are estimated at different stage in liaodong bay depression, by mean of combining analogue and structural analysis. Then, we confirm the relationship between extension and strike-slip of different tectonic units in the Liaodong Bey depression. The result of research shows that the extension and strike-slip relationships of different tectonic units are different in different periods. As for main faults in the eastern Liaodong Bay Depression, the extension displacements of Liaozhong 1 fault, Liaozhong 2 fault and Liaodong1 fault were larger than strike-slip displacements during Ek-Es4 deposition period, while the strike-slip displacements increased and exceed extension displacements during Es3-Es1depositiona period, the strike-slip displacements were significantly larger than extension displacements in the Ed-Nm depositional period. However, in the western Liaodong Bay Depression, Liaoxi 1, 2, 3 fault and Liaoxianan 1 fault possessed larger extension displacements than strike-slip displacements during Ek-Es1 depositional period, but from Ed Formation depositional period the strike-slip displacements increased significantly and were larger than extension displacements. So the Liaodong bay depression is dominated by extension in the Ek-Es4 depositional period. However, the strike-slip increased in the Es3-Es1 depositional period, but the extension was dominant in the western and strike-slip was dominant in the central and eastern. During Ed-Nm Formation depositional period, strike-slip was larger than extension.In summary, the interaction of extension and strike-slip is complicated of Liaodong Bay Depression in Cenozoic, and there are obvious transitions from intense extension with weak strike-slip to weak extension with intense strike slip from early Paleogene to Neogene, and the strike-slip strength of the central and eastern is obvious larger than the western in Liaodong Bay Depression.The interaction of extension and strike-slip resulted in different of fault sealing, trap types and oil-gas accumulation in different regions in the Liaoodng Bey depression.