Land Subsidence Monitoring in Tianjin with PS-InSAR Technique based on Sentinel -1 Data

Land Subsidence is one of the most important geological hazards in many areas. In order to prevent disasters caused by land subsidence efficiently, 24 Sentinel-1A images covering area of Tianjin are choosed from 2015 to 2018. Based on Persistent Scatterers InSAR technique, the results of land subsidence for three years are extracted using the precise orbit data and TanDEM-X DEM and compared with the monitoring results of SBAS (Small Baseline Subset) method. Combined with land use types, hydrogeological and traffic data, the characteristics and formation reasons of several subsidence areas are analyzed. The experimental results show that: (1) In recent three years, the land subsidence in Tianjin urban area is relatively slow, with an average speed of less than 8 mm/a. However, suburban land subsidence is still serious with an average speed between 50 mm/a~70 mm/a. The most serious land subsidence area was Wangqingtuo Town in Wuqing district, the total land subsidence was over 200 mm. And there is a trend of connectivity in these subsidence areas. (2) Land subsidence and the falling of groundwater levels have a very high spatial correlation and the difference between the cumulative shape variables obtained by the two methods of SBAS and PSInSAR is less than 5 mm. The results of this study can provide data support for the government of Tianjin.