Abstract: The relocation provides relatively accurate seismic parameters for the research of the seismicity and active tectonics. We relocated earthquakes occurred in the Beijing—Tianjin—Hebei and surrounding areas from December 2007 to March 2016 by the double-difference algorithm. Combined with the active faults data, we discussed spatial and focal depth distribution characteristic and its relationship to known active faults after relocation. Furthermore, we revealed the concealed fault according to space linear belts strike of the earthquake after relocation. The results show that relocated seismicity is concentrated in the Tangshan, Xingtai, west section of the zhangjiakou—bohai belt and Wenan region, the epicenters are more concentrated in space and around the fault planes than conventional seismic initial epicenters, and more reasonable in depth distribution with focal depths mainly concentrated in the 1~20 km upper crust layer. Relocation result shows that the Tangshan fault and Lulong fault are high angle faults dipping north-west, Xinghe fault is low angle fault dipping north-west. Seismic profile of Zhangbei region is nearly vertical distribution. In addition, according to seismic linear belts after relocation, it is revealed that the south of Tangshan fault and north of Wenan have two nearly NNE direction concealed faults.

Key words: Active fault, Focal depth, Seismicity, Double-difference location algorithm, Beijing—Tianjin—Hebei Area