Land subsidence in the modern Yellow River Delta based on InSAR time series analysis

To study the complex environmental characteristics of the modern Yellow River Delta (YRD), the interferometric synthetic aperture radar (InSAR) time series analysis technique based on 39 ERS1/2 SAR images was applied to obtain the spatial distribution and temporal changes of ground displacement of the YRD in the period of 1992-2000. The results show that land subsidence in the modern YRD is widespread and unevenly distributed with large differences. The average subsidence rate is -5.1 mm/year, while the highest subsidence rate of -33.2 mm/year occurs in the subsidence funnel formed in an oil field. The results of the InSAR are reliable, when compared with those measured by leveling surveys. In combination with various thematic maps, i.e., the river channels and shoreline changes, the distribution of the soft soil thickness, the development of residential areas and oil fields over the corresponding time period, and the effects of the factors controlling the land subsidence processes were determined in representative regions. Our results reveal that the factors leading to the land subsidence of modern YRD include oil extraction, sediment consolidation and compaction, surface load increases, and groundwater extraction. Our analyses also show that sediment consolidation and compaction, and oil extraction play a key role in contributing to the land subsidence in the modern YRD.