InSAR Surface Subsidence Observation In Beijing For The Past 30 Years And Evolutionary Trend Analysis

Land subsidence is the most common engineering geological hazard in major cities worldwide.Beijing,as the capital of China,is deeply affected by land subsidence,and it is becoming a negative impact on the sustainable economic development of the plain areas.Ground subsidence in Beijing occurred in the 1960 s,and in recent years,China’s rapid economic development,population explosion promoting accelerated urban construction and dramatic increase in groundwater resource consumption have become driving factors for the aggravation of ground subsidence in local areas of Beijing.However,the research on ground subsidence mechanisms and evolutionary patterns in Beijing has remained imperfect over the years,and past studies have only covered a limited period of time,and there has never been a complete history of subsidence to help understand the spatial and temporal evolutionary patterns of ground subsidence since the rapid development of Beijing.To address the shortcomings of existing studies in this regard,this paper acquired 22ERS-1/2 images from March 28,1993 to October 18,1999,49 Envisat ASAR images from June 18,2003 to September 29,2010,34 Radarsar2 images from January 28,2012 to May 12,2015,100 Sentinel-1A images from May 20,2017-November 19,2021 for joint monitoring of long time series ground subsidence in the Beijing area,and the SBAS-InSAR technique was used to obtain the time series deformation information in different time periods,and to fill the time interval between different SAR data sets,a stochastic statistical function was established based on the InSAR measurement data model.Then,the response characteristics of geological faults,groundwater dynamic changes,land use changes and other factors with ground subsidence in Beijing were analyzed by combining relevant hydrogeological data in Beijing.Finally,the spatial and temporal evolution of ground subsidence in Beijing and the subsidence mechanism are revealed.The main research contents and results of this paper are as follows:(1)Based on multi-source SAR data and SBAS-InSAR technique,land subsidence fields were detected in Beijing city area during different time periods from 1993-2021.The results show that from 1993 to 1999,local land subsidence was monitored in the eastern,southeastern,and northeastern parts of the main urban area,with a maximum settlement rate of-34.56 mm/yr,located in Chaoyang district.from 2003 to 2010,more severe land subsidence was monitored in Chaoyang district,western Shunyi district,and eastern Tongzhou district,and the three settlement zones began to merge,with a maximum settlement rate of-93.73 In 2015-2021,the maximum subsidence rate in Chaoyang District has reached-137.45 mm/yr,while that in Tongzhou District has decreased to-52.64 mm/yr.Overall,the subsidence centers in Beijing show a trend toward the east and northeast,with the subsidence in Chaoyang District gradually increasing and that in Tongzhou District gradually increasing.The subsidence phenomenon gradually increases in Chaoyang District,and the subsidence phenomenon in Tongzhou District is alleviated.(2)To further explore the evolution of ground subsidence in Beijing over a long time series,a stochastic statistical model was used to fit a multi-source data set to form continuous ground subsidence results for Beijing from 1993 to 2021.The analysis of the long time series subsidence results for typical subsidence targets shows that although Tongzhou district of Beijing has been in a state of subsidence since 1993,the subsidence rate shows a trend of gradual decrease,indicating that the subsidence phenomenon in Tongzhou district has been alleviated.Chaoyang District,on the other hand,has been in a state of accelerated subsidence,which is correlated with the population boom and industrial development in Chaoyang District.(3)In order to study the influencing factors related to ground subsidence in Beijing,correlation analysis was conducted with the data of Beijing city faults,groundwater level data and land use change data from 1993 to 2020 and ground subsidence.The results show that the spatial distribution of land subsidence in Beijing is consistent with the direction of geological faults,and there are differences in settlement,and the tectonic characteristics of settlement areas are jointly controlled by several geological fracture zones.With the continuous supply of water from the South-North Water Diversion Project,the groundwater level gradually rebounded,the underground loose layer absorbed water and expanded,and the ground subsidence phenomenon in general was alleviated,and the local area showed an uplifting trend.Finally,combined with the analysis of land use data,it is found that the area of land subsidence is positively correlated with the area of construction land and negatively correlated with the area of agricultural land,and it is believed that urban construction is also one of the causes of land subsidence.