Monitoring Land Subsidence of Mashhad Valley of IRAN Using Leveling, GPS Survey and InSAR Techniques

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Monitoring Land Subsidence of Mashhad Valley of IRAN Using Leveling, GPS Survey and InSAR Techniques

Original Article, D85
Amrouni Hosseini M. and Bayat H.
Journal. Civil Eng. Urban. 4(6): 562-567. 2014

ABSTRACT: In Northwest of Mashhad, one of the cities of Iran, land subsidence phenomenon is taking place highly due to the Irregular withdrawal of groundwater. Maximum transfer rate induced land subsidence is estimated about 23 cm per year by help of continuous GPS observations and precise levelling data provided by the National Cartographic Centre of Iran (NCC). GPS stations give precise continuous measurements but at a few sparse points of the deformed area. Therefore, they are not able to map the extent and pattern of the ground surface deformation caused by subsidence. Nowadays, the ability of In SAR in displacement of ground level continuous coverage with high spatial resolution has been proved with less than one centimetre accuracy. In this research, areas and the pattern of land subsidence was measured using the mentioned technique. 10 ENVISAT ASAR Radar images have been used to calculate 17 incremental interferograms and were determined by time series In SAR analysis of ground level in each radar data acquisition date. Present results revealed long and short term land subsidence changes in mentioned period. To detect land subsidence rates, the Average velocity map of movement were prepared with help of In SAR time series analysis results. Areas with different rates displacement was marked in this map. Based on this map, the maximum land subsidence rate was estimated about 24 cm. Comparing time series analysis results of In SAR and GPS measurements and precise levelling showed the high compliance of these data. Then an optimal GPS monitoring network was designed with image of the average speed of displacement to determine the horizontal displacement.
Keywords: Land Subsidence, Mashhad valley, Levelling, GPS Survey, InSAR Techniques.

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