Fault is one of the major factors that control hydrocarbon accumulation in the Bohai Sea waters. Based on seismic interpretation and structural mapping

this paper focuses on the characteristics and formation mechanisms of the Cenozoic faults in the Bohai Sea waters. In the study area

extensional and strikeslipping faults are the most predominant

and inverted faults are locally distributed. On plane view

most of the faults are of NE

NW or EWtrend

and the NEtrending faults mostly belong to the Tanlu strikeslip faut zone. While on sectional view

the faults occur as flower structures. The NWtrending faults are associated with the ZhangjiakouPenglai strikeslip fault zone

and constitute a conjugate shear faults system with the NEtrending faults during the neotectonic stage. The near EWtrending faults can be classified into two types according to their scale. The largescale EWtrending faults

acting as the boundary faults between the salient and trough in the southern part

experienced the early extensional and late strikeslipping movements. They exhibit quasiflower structures composed of major listric faults and shallow branching strikeslipping faults on the section. The smallscale EWtrending faults are densely developed in the shallow strata

and they are mostly derivative faults resulted from the strikeslipping movement of the Tanlu fault zone.