Time Series Investigation of Land Subsidence Using a Weighted Least Squares Adjustment Based on Image Mode Interferometric Data

摘要

This study presents the weighted least squares method based on Interferometric Synthetic Aperture Radarrn(InSAR) images to retrieve spatial-temporal evolution of land subsidence in Mashhad Valley, northeast Iran.rnUsing the analysis of a few interferograms covering the 2003-2005 period, Motagh et al (GJI 2006) presented arnpreliminary analysis of the subsidence in this area. Here we extend this study and use additional SAR data tornretrieve time-dependent deformation in Mashhad Valley We utilize 17 SAR images acquired by the ENVISATrnsatellite in a descending orbit during Jun. 2004-Nov. 2007, make 53 differential interferograms spanningrndifferent long- and short-term intervals, and do a time series analysis to extract deformation signals out ofrndifferential interferograms. Time series analysis suggests that the subsidence occurs within a northwest-southeastrnelongated elliptical shaped bowl along the axis of Mashhad valley. The maximum accumulated subsidencernduring 1260 days reaches about 86 cm, located northeast of Mashhad City. The comparison between InSAR timernseries results with continuous GPS station in the city of Tous, northeast of Mashhad, yields comparable results atrnthe level of 1 cm.