Characteristics of Surface Deformation in Lanzhou with Sentinel-1A TOPS

While surface deformations and their impact on buildings have been observed in the city of Lanzhou, it is difficult to find studies of surface deformation and the influential factors in the recent decades. This study was designed to detect the spatial position of these surface deformations and to understand the mechanism behind them. Sentinel-1A TOPS model image data acquired in descending orbits between March 2015 and May 2019 were processed by using Small Baseline Subsets Interferometry (SBAS)-Interferometric Synthetic Aperture Radar (InSAR) technology, and then compared with geology, tectonical aspects of the study area and land cover types in Lanzhou. The results reveal that the land surface deformation is uneven in this city, and seven surface deformation regions were detected in the following areas: the north freight yard, Jiuzhou, Country garden, Donggang, Yanjiaping, Zhongxinping and Liuquan town. The land surface deformation rate in Lanzhou ranges from -82.13 mm/year to 19.31 mm/year. Time-series land surface deformation analysis showed that deformation increased over time in major deformation regions. Surface deformation expansion was significant after June 2017and it continued to expand. The surface deformation of Lanzhou is affected by natural factors (geology and geological faults) and human activities (land cover types/land cover changes). Local geological conditions control the location of the surface deformation process. These findings provide compelling data and theoretical support for disaster prevention and reduction in Lanzhou.