In this paper, we present the results of D-InSAR technique and conventional leveling at selected area in Tianjin city, using 8 ENVISAT SAR images between 17 October 2003 and 17 February 2005.The D-InSAR results show that the subsidence rate reached over 5cm/year (7cm within 16 months) in highly sinking area, and it is consistent with leveling results. D-InSAR is able to provide more details of urban subsidence, and it is supplement to leveling surveys in those areas with sparse leveling benchmarks.

Using the model data for surface mass changes of the atmosphere, ocean, soil moisture and snow depth, the vertical crustal displacements of 25 ficual stations in China were calculated according to the loading theory. From the spectral analysis of the results, we can see that the periods of displacements are 12 months and the semi-periods are 6 months. The results also show that the maximum seasonal displacements can reach 20 mm and even larger. The covariance analyses and significance tests show that the coefficients of 96 percent of the stations are significant at the 0.1 significance level. The results show that one of the reasons of the vertical crustal displacements is the changing surface fluid loads.