Abstract: Vertical deformation gradient can effectively reflect the rate of vertical change in the unit distance, and vertical deformation velocity gradient can reflect the strength of the earth's crust tectonic activities. In this paper, we use long period leveling data combined with GPS data to calculate vertical deformation gradients. Leveling and GPS are two different means of monitoring, but the result is approximately the same in vertical deformation gradient. The calculation results show that the relevance of the spatial distribution of vertical deformation velocity gradient and tectonic distribution is obvious. The most significant gradient anomalies in the North—South Seismic Belt appear on the Xianshuihe fault, Longmenshan fault and Xiaojiang—Zemuhe fault, the second gradient anomalies in the northeastern Tibet plateau appear on the Zhuanglanghe fault and Lenglongling fault, and the 2016 Menyuan M6.4 earthquake occurred in this abnormal area. From the high gradient distribution of vertical deformation, there is also possibility of earthquake around Tianzhu and Jingtai. The tectonic activities of North—South Seismic Belt has become stronger especially in the intersection area of the three major fault zone.

Key words: Vertical deformation, Velocity gradient, The North—South Seismic Belt, Earthquake activity