Land Subsidence Monitoring By Ascending And Descending InSAR And Analysis Of Temporal And Spatial Characteristics In Beijing

The Beijing Plain area has a sag of more than 1,000 meters thick loose sediment,which is easy to cause land subsidence in this area.Since 1935,the Beijing area has been affected by land subsidence.In order to prevent the occurrence of land subsidence,the Beijing Municipal government adopted a series of measures such as groundwater control on surface deformation,which effectively controlled the groundwater exploitation in Beijing area.The implementation of the Middle Route Project of the South to North Water Diversion in China at the end of2014 has solved the problem of water resource shortage in Beijing to some extent,alleviated the water consumption of groundwater,and gradually became the main source of water supply in Beijing.In order to better study the evolution process of long-term land subsidence in the Beijing area,we use ENVISAT ASAR and Sentinel-1 data from 2003 to 2020 to monitor and analyze Beijing’s land subsidence using temporal In SAR technology.We combine multi temporal SAR satellite data to interpret the spatiotemporal evolution characteristics of Beijing’s land subsidence before and after the opening of the Middle Route of the South to North Water Transfer.The research provides data support for long-term land subsidence monitoring and water resource management in the region.The main content and conclusions of this study are as follows:(1)The study utilized a fully functional SAR data processing software developed by Swiss company GAMMA Remote Sensing AG,using 224 images of the ascending and descending Sentinel-1 covering the Beijing area.Based on small baseline set technology and robust least squares fitting method,the fusion results of the ground deformation of the ascending and descending in Beijing from 2015 to 2020 were obtained.At the same time,GNSS monitoring data was used to verify the accuracy of the fusion results.The results show that the GNSS monitoring deformation is in good agreement with the ascending and descending fusion deformation,the absolute error between them is less than 10mm/yr,and the correlation is 0.95.(2)We used ENVISAT ASAR data covering the research area from 2003 to 2010 and Sentinel-1 data from 2015 to 2020 to calculate surface deformation in Beijing.And we obtained the annual average rate and cumulative deformation results of ground subsidence from 2003 to 2010 and 2015 to 2020,respectively.We used quadratic polynomials to fit the surface deformation results of the two time periods and obtained the spatiotemporal evolution law of Beijing’s ground subsidence before and after the opening of the Middle Route of the South to North Water Diversion Project.This study not only provides important deformation information for the Beijing area.In addition,the research results have important reference significance for stability analysis,large-scale engineering construction,and urban planning in Beijing.(3)The paper analyzes the causes of surface deformation in Beijing by combining land use types,groundwater,and rainfall data.The results indicate that compared with other land use types,construction land is more prone to land subsidence;During concentrated rainfall,there is a significant rebound deformation phenomenon along the radar line of sight;In addition,as the groundwater level rises,the rate of land subsidence shows a slowing trend.Analyzing the correlation between construction land,rainfall,groundwater level,and land subsidence,it was found that the impact of land use type and precipitation on land subsidence is relatively small,and changes in groundwater level are the main factors causing land subsidence in Beijing.