A study of land subsidence in west of Tehran using Sentinel-1 data and permanent scatterer interferometric technique

In recent years, subsidence is considered one of the major environmental challenges in semiarid and arid regions of Iran. The main reason of land subsidence in Iran is injudicious groundwater extraction for agricultural and industrial activities. This study focuses on monitoring the displacement level of the ground in the west of Tehran which is highly affected by subsidence of Shahriar and Tehran plains. To support this study, Sentinel-1 images in both ascending (28) and descending (35) paths were used. The maximum subsidence rates of 16 cm/year and 15 cm/year were estimated in the southwest of Tehran and Shahriar Plain, respectively. Three subsidence centers were discovered in Shahriar Plain which is located in an urban area. The maximum LOS velocity was calculated about 5 cm/year in Fath Highway. The maximum rate of subsidence was estimated approximately 20-70 mm/year in the vicinity of Qods City. In Shahriar Plain, accuracy of InSAR results was assessed using cross-comparison analysis of the ascending and descending paths. However, in the southwest of Tehran, the vertical velocity obtained from Sentinel-1 data is validated using the GPS observations. The validations confirmed the accuracy of the PSInSAR algorithm and the InSAR results.