A Study of land Subsidence in West of Tehran Using Sentinel-1 Images and Permanent Scatterers Interferometry

During the past decades, Tehran has suffered from subsidence crisis. Prolonged droughts and excessive exploitation of groundwater for agricultural and industrial purposes have reduced the level of aquifers and reduced the density of the subsurface soil layers. This study focuses on monitoring the displacement of the ground in west of Tehran which is affected by subsidence of Shahriyar and Tehran plains. A time series of 30 Sentinel-1 images were processed by radar interferometry technic based on the persistent scatterers in two years. Average annual displacement map was prepared for the region of study. The result of study indicates 15 centimeters of displacement in southern part of the study area where it ends to Shahriyar and Tehran plains. However, displacement is not limited to plain and non-urban areas. It has also scattered through industrial and urban areas. In industrial and residential areas, cumulative displacement of 9 to 13 centimeter was recorded in two years especially in Fath Highway which experiences more than 4 centimeters of displacement each year. Relative evaluation of results was made based on the data gathered from underpass 35. Considering the small difference in the estimates obtained from orbits 28 and 35, these areas had little Horizontal displacement. Displacement vector was high in vertical movement. Vertical displacement was computed for ascending and descending orbits in the second study region and verified by data from a GPS station.