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The Control Effect of Bohai Sea Area (East China) Cenozoic Fault System to Its Internal Basin Structure

Abstract

Based on detailed 3D seismic interpretation, coherence time slice, along-horizon attribute slice and 3D visualization techniques, and combining with previous research results, this paper analyzes the control effect of the Bohai Sea area cenozoic fault system to its internal basin structure. And the results show that: under the combined action of the subduction (NWW-trending) of Pacific plate towards Eurasian plate, the collision (NE-trending)) of Indian Ocean plate and Eurasian plate and mantle unwilling, Bohai Sea area develops a coexistent stress environment of strike slip and extension. In response to this stress environment, Tanlu faults zone (TLF, located in the east of the Bohai Sea area, dextral Riedel shear or “R”) (composed of a series of NNE trending main faults) and Zhangjiakou-penglai faults zone (ZPF, sinistral conjugated Riedel shear or “R'”) (divided in to north and south two branches, composed of a series of NW or nearly EW-trending main faults, and mainly distributed in the west of TLF) come up conjugate strike-slip movement. And in the east of TLF (Bozhong part) a series of NE-trending extensional faults (“T” faults) and between the east and west branches of TLF (Bonan part) a series of nearly EW-trending faults (caused by pull-apart stress) were derived. According to the above faults’ distribution and their fault mechanical properties, the basin structure of Bohai Sea area could be divided into five different tectonic systems: 1) North part (Liaodongwan Depression, located north of ZPF north branch) is a graben-horst tectonic system, which is controlled by NNE-trending strong strike-slip TLF (Liaodongwan part) and its parallel derived strike-slip-extensional faults.2) East part (Bodong and Miaoxi area, located east of TLF (Bozhong part)) shows as a brush tectonic system with the NNE-trending strike-slip faults as its main branches, NE-trending tensional faults to secondary ones.3) Central part (Bozhong sag located east of NNE-trending TLF(Bozhong part), between north and south branches of ZPF) displays as a bucket tectonic system developed under the conjugate strike-slip movement of strike-slip TLF and extensional-strike-slip ZPF.4) West part (Boxi area) is a rollover half-graben tectonic system controlled by NW-trending ZPF strike-slip-extensional branches. 5) South part (Bonan area, located between strong strike-slip TLF (Bonan part) and strike-slip-extensional nearly EW faults) shows as pull-apart tectonic system.