Land Subsidence in Beijing’s Sub-Administrative Center and Its Relationship with Urban Expansion Inferred from Sentinel-1/2 Observations

摘要

Beijing’s Sub-Administrative Center (BSAC) is located in the South-eastern Beijing Plain,which exhibits severe subsidence. The rapid urban expansion in recent years has aggravatedland subsidence and threatens the safe operation of Beijing. First, this study applied the persistentscatterer-interferometric synthetic aperture radar (PS-InSAR) to extract BSAC subsidencetime series data. Second, combined with the index-based built-up index (IBI),expansion intensity index (EII), and expansion gradient index (EGI), the spatiotemporal characteristicsof urban expansion were retrieved from optical data. Finally, we examined theurban expansion effects on land subsidence at the regional and single-building scales. Theresults showed that the maximum subsidence velocity in the BSAC reached 121mm/yearfrom 2015 to 2018, and the urban construction land area increased by 22%. At the regionalscale, there existed a positive correlation between land subsidence and EGI or EII. This indicatedthat urban expansion had a certain impact on land subsidence. Therefore, we furtherexplored the relationship between construction and land subsidence at the single-buildingscale. The engineering construction effects on land subsidence were divided into three periods,namely, rapid settlement, rebound, and stable periods. Although construction had asignificant influence on land subsidence, it did not cause subsidence mutation.