Objectives As one of the most important active faults in Shandong province, Yishu fault zone has always been concerned by scholars at home and abroad. Obtainment of the characteristics of differential movement of the crust on both sides of the fault zone and establishment of a refined surface velocity model can provide a scientific basis for the more effective strong earthquake risk assessment of the fault zone.
Methods First, the vertical deformation rate field of the Shandong area is obtained by using the time series data of 44 global navigation satellite system reference stations from 2011 to 2018. Then, the vertical movement profile characteristics of the area near the fault zone are obtained, and the vertical differential movement on both sides of the fault zone is analyzed. Finally, the velocity gradient field is calculated, and the difference in the deformation rate of the area is obtained.
Results The results show that the relative subsidence of both sides of the fault in the Yishu fault zone is obviously different, and the overall subsidence is in the state of east rising and west falling, with the level of 2.0 mm/a. The subsidence rate on the east and west sides of the northern section of the fault zone is significantly higher than that of the southern section, which is about 4.0 mm/a. The Changyi section of the fault zone has a large vertical deformation rate gradient.
Conclusions At present, the northern section of the Yishu fault zone has similar characteristics to seismic gaps: minor earthquakes and the crustal movements in this zone are all weak. And it is prone to stress accumulation. It is necessary to focus on its seismic risk.
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