Abstract:Based on the artificial shallow seismic reflection profile, we find that the Baodi fault in Jingzhuang area of Xianghe county is a nearly EW trending normal fault with a spade-shaped profile. It is an active Quaternary fault and controls the deposition of Quaternary. Judging from the comparison of structural observation drilling cores on both sides of the fault and the data of 14C dating and OSL dating, the up-breakpoint of Baodi fault is about 5-7 m away from the surface, its main activity occurred in Late Pleistocene, and there is no obvious activity in Holocene and late Middle Pleistocene. The comparison of the cores shows that in the last 100 000 years, the Baodi fault has been seismically active twice, with a cumulative displacement of 2.6 m. The recent earthquake occurred at 22 740±70 a BP with a co-seismic displacement of 1.4 m; the other earthquake occurred between 97.1±4.4 ka and 98.0±5.3 ka with a co-seismic displacement of 1.2 m. According to the drilling research, combined with previous research results on fault activity and seismogenic laws in the eastern section of Zhangjiakou-Bohai tectonic belt, we conclude that the Baodi fault has been inactive since Holocene, and the possibility of inducing moderate and large earthquakes is low. In addition, the Jingzhuang ground fissures in Xianghe county are structural ground fissures controlled by the Baodi fault. The shearing stress caused by the uneven ground subsidence on both sides of the Baodi fault also accelerates the development of the Jingzhuang ground fissures.
ZHANG Huan,XU Kang,WANG Hui et al. Study on the Activity of Baodi Fault Since Late Pleistocene in the Northern Margin of North China Basin[J]. jgg, 2021, 41(11): 1169-1176.