Abstract: The Hexiwu Fault is an important boundary fault in the northern Jizhong Depression of the Bohai Bay Basin. It remained
active during the Neogene and Quaternary, when the Bohai Bay Basin entered the thermal depression stage. The earthquake occurred
in Yongqing, Hebei province at 2018 was triggered by activities of this fault. This paper analyzes the structures of the Hexiwu Fault and
its activities during the Neogene and Quaternary using seismic data. Results show that the fault has been dextral transtensional since
the Neogene. It presents negative-flower structures on profiles and is segmented on map view, with the northern and southern segments
of dextral transtensional deformation and the middle segment being dominated by dextral deformation. A kinematic model suggests that
those segmentation features may be determined by the angles between fault orientation of each segment and the dextral shear direction
in this region.

Key words: Bohai Bay Basin, Jizhong Depression, Hexiwu Fault, active faults, earthquake hazard