Refference : The 25th Symposium on Geoscience;Tehran
Publishing Year : 1385

Abstract :

Based on the measurements carried out by the National Cartographic Center of Iran it reveals that an area located in the 20 Km of the north west of Mashhad is subject to the land subsidence due to the excess groundwater withdrawal. GPS and precise leveling measurements show a very high deformation rate in the area. However, these methods are able to map the displacement in a few sparse locations. Therefore, for the first time in Iran in order to map the extent of the land subsidence in a very high spatial resolution, Remote Sensing group of the Geological Survey of ban (GSI) used the Interferometric SAR technique (InSAR) to represent the subsidence pattern. Furthermore, time series analysis of a significant number of interferograms was applied in order to study the temporal characteristics of the deformation over the whole area. The average rate derived from the Interferometric time series analysis is 10 to 15 cm per year. The interferometry results were then compared to the GPS and precise leveling. The comparisons showed a great agreement between these three methods. The results obtained by time series analysis shows the increasing subsiding of the aquifer system level during the time. Moreover, according to the time-varying behavior of the subsidence the seasonal changes are very negligible compared to the long-term deformation. Hence it can be concluded that the underground water resources in that area are not recharged during the winter.

Subject List : Remot Sensing Application