Monitoring And Mechanism Research Of Land Subsidence In Fenwei Basin Using Time Series InSAR Technology

Land subsidence is a long-term and slow geological disaster caused by human activities(such as groundwater exploitation,mining,urban construction)or natural factors(such as earthquake,precipitation).By 2020,land subsidence has occurred in more than 50 counties and cities in the Fenwei Basin,forming more than 180 ground fissures.Long-term continuous monitoring is the most efficient means of ground subsidence disaster prevention and cure.However,there are few studies of long-term and large-scale surface deformation monitoring in Fenwei Basin,and the causes of surface deformation need further study.Therefore,the demand for monitoring the long-term temporal and spatial distribution of land subsidence in the Fenwei Basin and analyzing the formation mechanism of land subsidence in the main deformation areas of the basin is increasing.Compared with traditional measurement methods such as leveling,trigonometric leveling and global navigation and positioning system(GNSS),time-series InSAR technology has the characteristics of all-day,all-weather,large coverage scope,low monitoring cost,high spatial and temporal resolution,and can monitor surface deformation with centimeter level or even millimeter level accuracy.In this paper,the time-series InSAR method is used to obtain the land subsidence results of the Fenwei Basin from 2007 to 2021.The accuracy of the InSAR results is verified by the GNSS precision time series products of the land state network.Combined with fault data,precipitation data,groundwater data,mining data,nighttime lighting data and other data,key driving factors of the main subsidence areas in the basin is studied.The research contents and results of this paper are as follows:(1)The GACOS-assisted SBAS(Small Baseline Subset)InSAR was used to process 568ALOS-PALSAR images and 921 Sentinel-1A images,and surface deformation monitoring results of Fenwei Basin from 2007 to 2021 were obtained.The results show that the Fenwei Basin is relatively stable,and land subsidence mainly occurs in Datong Basin,Taiyuan Basin,Linfen-Yuncheng Basin and Weihe Basin.Subsidence of Datong Basin is still intensifying,land subsidence in Taiyuan Basin,Linfen-Yuncheng Basin and Weihe Basin shows a decreasing trend.The accuracy of InSAR results is verified by the terrestrial network GNSS precision time series products.The average error is 3.69 mm/yr,and the maximum error is less than 5 mm/yr.The correlation of the InSAR stitching results of adjacent tracks in the overlapping area is greater than 0.85,and the root mean square error is better than 10 mm/yr.(2)Combined with the deformation time series and numerous external data,the key driving factors of each sub-basin is revealed.The mining activities continue to be carried out in the western mountainous area of Datong Basin,forming obvious subsidence funnels.The surface subsidence caused by underground mining in the mining area generally shows an ’S’ change trend.Land subsidence of Taiyuan basin is controlled by Jiaocheng fault and Taigu fault.The land subsidence in Jiaocheng-Qingxu subsidence area is mainly due to the exploitation of groundwater by industrial water.Subsidence of Taiyuan city in the north of the basin is mainly due to the exploitation of groundwater by domestic and industrial water.Taigu-Qixian subsidence area is a major agricultural production area,and land subsidence is greatly affected by precipitation.Multiple mining subsidence funnels are formed by mining in Xiaoyi-Jiexiu subsidence area.Luoyun mountain fault,Mingtiao mountain fault and Zhongtiao mountain fault control the spatial distribution of subsidence area in Linfen-Yuncheng basin as a whole.Overexploitation of groundwater is the primary reason of land subsidence in this area.The response of surface deformation to the change of groundwater head has a certain lag period.Urban expansion also has a certain impact on land subsidence in the basin.