Abstract:

Shunyi fault is one of Quaternary active faults in northeastern Beijing plain. Its activity is regarded as one of potential geological disasters to the urban security. In order to reveal the activity history of Shunyi fault,the magnetostratigraphy research was conducted on borehole ZK12-1 at the footwall of fault. The detailed stepwise thermal demagnetization isolated two components，and the characteristic remanent magnetization (ChRM) with moderate downward or upward inclinations was identified after removing a low-stability drilling-induced remanence with steep downward inclinations.Combined with the lithologic association of the core，a magnetostratigraphic frame of borehole ZK12-1 was established. Based on the magnetostratigraphic framework of borehole ZK12-1 at footwall and borehole ZK12-2 at the hanging wall and the distance of the vertical movement，the vertical activity rates between the hanging wall and footwall of Shunyi fault were computed to be 0.023 mm/a in the Early Pleistocene，0.001,7 mm/a in the Middle Pleistocene，0.033 mm/a in the Late Pleistocene and 0.051 mm/a in the Holocene. These results indicate Shunyi fault activated strongly in the Early Pleistocene and activated weakly in the Middle Pleistocene. In the Late Pleistocene，this fault became much more active，and in the Holocene it experienced the strongest activity.

Key words: magnetostratigraphy, Shunyi fault, Beijing Plain, activity rate, Quaternary