Land surface deformation in Nanchang, China 2018–2020 revealed by multi-temporal InSAR

Abstract

With the influence of rapid urbanization, land subsidence in Nanchang has caused obvious surface cracks in urban roads. It is necessary to use effective deformation monitoring methods to grasp the current situation and causes of land subsidence in the urban area of Nanchang. Multi-temporal C-band Sentinel-1A images were processed by Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS InSAR) technique, and we obtained the land deformation in Nanchang urban area from 2018 to 2020. Deformation rate results show that most of the land in the study area was stable, and about 94% of the monitoring points had a deformation rate of −5 to 5 ​mm/year. However, small-scale subsidence occurred in the west, north, and south of the study area, with the maximum subsidence rate of −30 ​mm/year. Compared with the leveling data, InSAR-derived results reached the centimeter-level accuracy. Time-series deformation analysis reveals that the main factors causing land subsidence were urban constructions, including building construction, vehicle load, and Nanchang Metro operation. The most severe settlement in the study area was caused by vehicle load, which had significant spatial distribution characteristics. In addition, the acute subsidence that occurred in the construction and early operation stages of the metro gradually stabilized in less than two years.