Evolution of land subsidence over Beijing, China revealed by MT-InSAR technology.

Regional land subsidence is an integrated systematic issue related to multidisciplinary andbeing of global focus, and has been being a serious threat to the urban infrastructure,high-speed railway and the utilization of underground space, and restricting the sustainabledevelopment of society. The study of the regional subsidence evolution in Beijing Plain is ofgreat significance: it is necessary to reveal the regional land subsidence evolution law underthe background of Integration of Beijing-Tianjin-Hebei and the South-to-NorthWater Diversion. Furthermore, it can help to realize the scientific regulation ofregional subsidence and ensure the sustainable development of regional economy andsociety, which has a special significance and application prospect. Therefore theMT-InSAR method is used to obtain the regional ground subsidence time seriesinformation of the study area in three periods: Jun. 2003 ∼ Aug. 2010, Oct. 2010 ∼ Nov.2015, and May. 2015 ∼ Jun. 2018. Then equations are established based on thetime-overlapping information to complete the fusion of multi-platform time series, theinconsistence between different reference points is solved, simultaneously. Theresults show that, the maximum subsidence values in Beijing Plain are 690.6 mm,649.2 mm and 411.7 mm during the three periods, with maximum deformationrates of 100.6 mm/a, 130.0 mm/a and 142.3 mm/a, respectively. For the spatialdistribution and the evolution of the land subsidence field, the weighted spatialkernel density analysis, profile analysis, trend-surface analysis and profile-gradientanalysis are used to analyze the spatial-temporal evolution characteristics of theland subsidence field. In this case, land subsidence in Beijing Plain are thoroughlyanalyzed overall distribution characteristics and evolution process. Nine subsidencecenters are identified and the subsidence centers are connecting to form a mainsubsidence area in the northern part of Beijing Plain. The spatial clustering degree ofthe subsidence in the Beijing Plain indicates an overall heterogeneity in spatial.Moreover, the northern subsidence areas spread along the Nankou-Sunhe fault, and iscut into several subsidence centers by active faults, indicating that the regionalgeological structure has obvious control effect on the spatial distribution of landsubsidence areas. The evolution of the subsidence field: the northern subsidence areasspread along the northwest-southeast direction, and then expands to both the east andwest sides. Then through the distribution of subsidence areas and groundwaterfunnel, the InSAR based time series and the monitoring well based groundwater levelchanges, the correlations in spatial and responses between land subsidence field andgroundwater flow field are analyzed. The results show that the subsidence centerin the northern Beijing Plain is consistent with the groundwater drop funnel inspatial, with a similar downward trend over the whole observation time. Through theanalysis of well based results located in different areas, the long term groundwaterexploitation in the northern subsidence area has led to the continuous decline ofthe water level, resulting in the inelastic and permanent compaction; while for themonitoring wells located outside the subsidence area, the subsidence time seriesshow obvious elastic deformation characteristics as the groundwater level changes. [ABSTRACT FROM AUTHOR]