Monitoring of surface deformation and its spatiotemporal characterization in Tongling City of Anhui Province based on time-series InSAR of Sentinel-1 data

YANG Chen; JIN Yuan; DENG Fei; SHI Xuguo

doi:10.11932/karst20250310

Abstract：Tongling City,located in the south-central part of Anhui Province on the southern bank of the middle and lower reaches of the Yangtze River,lies within the hilly region of the riverine plain and experiences a subtropical humid monsoon climate.With a total area of 2,991.87 square kilometers,it is a crucial region within the Wanjiang Economic Belt.Renowned as the "Ancient Copper Capital of China",Tongling is abundant in natural resources,particularly minerals,including copper,sulfur,iron,gold,silver,coal,and limestone.As a significant mining area in China,there are currently 220 licensed mines in Tongling,which are extracting 30 million cubic meters of ore annually,with a total mining and processing output exceeding two billion yuan.The carbonate rock strata in Tongling are highly developed,with a cumulative thickness of over 1,500 m.These strata are primarily concentrated in the Middle-Upper Carboniferous to Lower Permian and Middle-Lower Triassic geological periods.Due to factors such as mining dewatering and groundwater pumping,Tongling has been vulnerable to geological hazards such as karst collapses. The sites with potential geological hazards are typically found in regions exhibiting clear signs of surface deformation.Real-time monitoring of surface deformation allows for comprehensive identification of the sites with potential geological hazards and timely early warnings.The simple monitoring methods,such as pile-embedding and painting to observe known hazard sites,have been employed;however,these techniques cannot capture large-scale subsidence data,making it difficult to detect and monitor unknown hazards.In recent years,Interferometric Synthetic Aperture Radar(InSAR)has been widely used as a large-scale,high-precision deformation monitoring tool.It offers several advantages over traditional methods,including all-weather capability,continuous operation,extensive spatial coverage,and high accuracy.With the development of time-series InSAR techniques like Persistent Scatterers InSAR(PSI)and Small Baseline InSAR(SBAS-InSAR),high-precision surface deformation monitoring using coherent pixels within InSAR data has become increasingly important in identifying and monitoring geological hazards. This study focuses on Tongguan District and Yi'an District in Tongling City,situated in the south-central part of Anhui Province,along the southern bank of the middle and lower reaches of the Yangtze River.The study area boasts extensive soluble rock distributions and rich mineral resources like gold,silver,copper,iron,and sulfur,with a mining history spanning over 3,500 years.Consequently,geological hazards like karst collapses and mining collapses are prevalent.Fig.1 marks 130 locations of historical karst collapse,primarily concentrated near Shizishan in Tongguan District.Fig.1a illustrates the terrain and karst development within the study area,while Fig.1b depicts the landform,characterized by higher terrain in the south and lower,flat terrain in the north(the Yangtze River alluvial plain,with elevations ranging from 6.5 to 20 m)and hilly terrain in the south(with significant topographic relief and elevations generally between 50 and 250 m,peaking at 493 meters at Tongguan Mountain). This study utilizes SBAS-InSAR technology to process Sentinel-1 data covering Tongling City,identifying local deformation zones from 2015 to 2021,including the Xinqiao Mining Area,Laoyaling,Bijia Mountain,and Liuguo Chemical Plant.The maximum deformation rate,observed in the Xinqiao Mining Area,is approximately 118 mm/yr.Analysis of these deformation zones indicates that the combined effects of karst geological conditions and human activities like mining have contributed to the observed deformation characteristics.Notably,deformation in the Laoyaling tailings pond is also influenced by rainfall.Our findings demonstrate that InSAR technology can be effectively employed for large-scale geological hazard identification and monitoring,providing vital information for disaster prevention and control.For areas with significant deformation,it is recommended to install corresponding ground monitoring measures to assess risks in detail.With the launch of China's land exploration satellites and future satellite missions,abundant SAR satellite data will become available for more detailed analysis of deformation characteristics,enabling more precise monitoring and assessment of hazard sites.InSAR technology will play an increasingly critical role in disaster monitoring in this region.