Neotectonics in the western and central Bohai Sea

From the high resolution single-channel seismic reflection data recently acquired, the sediment thickness of the middle Pleistocene, upper Pleistocene, Holocene and the sediment thickness since middle Pleistocene to Holocene are produced.Results reveal that affected by the Himalayan orogeny, the stress field of the region has changed from a weak stretching environment of post-rift thermal subsidence to a NEE-WE horizontal compressive stress field.Sedimentation was then differentiated in two subsiding centers of the Bozhong depression and north-central Qikou depression before Quaternary.During the early and middle Pleistocene Epoch, the Zhangjiakou-Penglai fault zone and the Qinhuangdao-Lvshun fault zone were leftlateral strike-slip fault zones along the NW direction.Under the control of the Qinhuangdao-Lvshun fault, significant differentiation of subsidence occurred and the subsidence center moved to the north.Isopach map displays a preferential NW orientation.Conjugated and newly generated NE Yellow River estuary-northwest Miao fault zone was activated as a dextral strike-slip shear zone.The southern part of the Tanlu fault zone was inactive at least before middle Pleistocene, due to its NNE trending prohibited by a regional stress field.This region suffered regional isostatic subsidence during the period from late Pleistocene to Holocene, while the activity of the fault zone became weak, and the number of faults decreased significantly.