The Northern Xiqinling fault zone is located at the northeast edge of the Tibet Plateau, which is one of the largest active faults in northern region of the plateau and the key earthquake hazard area in Gansu province.During the most recent decade,many large earthquakes have occurred in succession near the rim of Bayan Har Block,including the Mani MS 7.9earthquake on the western border,the KunLun MS 8.1earthquake on the northwestern border,the Wenchuan MS 8.0and Lushan MS 7.0earthquakes on the eastern border.The spatial and temporal variation characteristics of these seismic events show that the Bayan Har Block has entered a new period of seismic activity,which has enhanced the earthquake risk of the adjacent areas including the Qaidam and Qilian blocks.Therefore,continued research of seismic hazards and background fields of the Northern Xiqinling fault zone are necessary.In this study,we surveyed the spatial distribution characteristics of fault gas concentration on the Northern Xiqinling fault zone.The hazard area was predicted according to the spatial concentration anomaly values of Hg and Rn soil gas combining with the seismotectonic background and spatiotemporal evolution characteristics of large historical and recent earthquakes.We conclude that the tectonic background of large earthquakes at the F1and F4segments of the Western QinLing fault zone includes few small earthquakes,a lengthy period since the most recent large earthquake,and a low gas concentration of Hg and Rn.In comparison,the F3segment of the Northern Xiqinling fault zone showed frequent small earthquakes,a short period since the most recent large earthquake,and a high gas concentration of Hg and Rn.This research can provide vital background information for earthquake prediction.