Evaluation of the Nankou-Sunhe fault activity in Beijing based on the characteristics of magnetic strata and sedimentary strata

Nankou-Sunhe fault is one of most importance active faults in Beijing plain and one part of Bohai Bay-Zhangjiakou fault belts. This paper builds magnetic polarity chronology of borehole sedimentary strata based on magnetic stratigraphy and sedimentology with drilling and paleomagnetism and ¹⁴C samples testing, analyses and discusses the active features of NankouSunhe fault in the north segment since Quaternary period. The research indicates that:the fault activity changed from high to low intensity in the early stage of early Pleistocene(2.58-0.99 Ma)and turned into high intensity in the late stage of early Pleistocene (0.99-0.78 Ma), from strong to low intensity again in the Middle Pleistocene (0.78-0.126Ma), and then from low to high again intensity (0.126 Ma-present). This active feature is consistent with west mountain of Beijing uplift which shows the characteristics of high-low-high intensity.