Abstract: In this paper, on the basis of detailed field geological survey, the features of the faults revealed by digging trenches, the surficial features of faults at the eastern side of Beichuan River, Nanchuan River and Huangshui River in Xining City are presented. Through the previous thermo-luminescent dating, we find that the fault at eastern side of Beichuan River cut the second-order to third-order terraces crossed by fault; the third-order terraces formed 0.12 Ma ago. It shows that this fault has been not active since late Pleistocene; Nanchuan River fault cut the four-order to fifth-order terraces crossed by fault, the four-order terraces formed 0.54 Ma ago. It shows that this fault has been not active since early Pleistocene; Huangshui River fault cut the second-order to third-order terraces crossed by fault. It shows that this fault has been not active since late Pleistocene. Small scale and weak activity of those faults show that they possibly belong to superficial faults.

Key words: Active fault, Xining City, Cross-section of trench, Surface features