Abstract: Wavelet transform analysis method is utilized to extract the long-term trend component of both mobile short leveling and long leveling observations at the Yishu fault zone and its branch faults, and vertical deformation rate and stress state are calculated and analysed. The results show that: The vertical deformation rate of the Yishu fault zone and its NW branch faults are small, with no obvious abnormal rate and stress state change. The same fault may have piecewise and time-sharing activity characteristics, and fault activities are basically consistent with the geological investigation results. Vertical deformation rate and loading mode of most of the leveling observation fields changed before and after the Cangshan M5.2 earthquak in 1995 and the Japan M9.0 earthquake in 2011. Several abnormal obsvervations of across fault leveling in Shandong province in recent years mainly have come to an end and there are some interference factors in the only remaining Fengjiafangzi leveling abnormity, so the crustal deformation background for a strong earthquake in the recent future is not obvious.

Key words: Yishu Fault Zone, Vertical deformation, Wavelet transform analysis method, Leveling observation