Different-scale Surface Deformation Monitoring In Zhangjiakou With InSAR Technology

Zhangjiakou is an important part of the Beijing-Tianjin-Hebei synergy development national strategy.This region has unique geographical conditions and diverse mineral resources.The Zhangjiakou area is also located at the intersection of the Zhangjiakou-Bohai fault zone and the Shanxi seismic belt,where the geological structure background is complex and earthquakes occur frequently.The research of high-precision and multi-scale surface deformation monitoring in Zhangjiakou area has important practical and scientific significance.Interferometric Synthetic Aperture Radar(InSAR)technology has become a new measurement method due to its advantages of all-time,all-weather and wide coverage.The monitoring accuracy of conventional differential InSAR(D-InSAR)is easily affected by factors such as system noise,spatiotemporal decorrelation,and atmospheric delay.In order to overcome these errors,various multi-temporal InSAR methods have been developed in recent years,these methods are widely used in surface deformation and geological disaster monitoring.The application of InSAR technology in Zhangjiakou area is insufficient,therefore,this paper uses a variety of InSAR technologies to monitor large-scale and high-precision surface deformations in the area.The characteristics of surface deformation at different scales,such as urban land subsidence,tectonic fault activities,and underground mining collapse,are analyzed.The research results provide data reference for geological disaster monitoring and ecological environment construction in Zhangjiakou area.The main researches contents and achievements are as follows:(1)Analyzes the basic principle of InSAR technology,sorts out a variety of multi-temporal InSAR technologies proposed in the past 20 years,and summarizes the technical characteristics and application scenarios of each method.The error factors of InSAR are studied and the common methods of weakening and removing are given.(2)The geological tectonic background and the natural geographical environment of Zhangjiakou-Bohai fault zone are investigated.InSAR technology is used to monitor and study the surface deformation of different scales in Beijing and Zhangjiakou areas.Among them,the Beijing area focused on the study of the spatiotemporal evolution characteristics of the subsidence area in the eastern Beijing Basin and the ground fissures caused by the uneven settlement of the Beijing Capital International Airport.The results showed that the maximum annual deformation rate in the eastern subsidence area of Beijing basin was more than-120 mm/year,and the differential deformation rate at both ends of the runway reaches 38 mm/year;the Zhangjiakou area focuses on studying the activity characteristics of multiple tectonic faults and the surface stability of the mountainous area around Chongli county.The results show that the characteristics of fault activities in Zhangjiakou area are not obvious.The surface stability of the area where the Winter Olympic Games venues are located is good,and the local areas have potential geological hazards risk due to mountain damage.(3)Taking the Yuxian mining area in Zhangjiakou as the research object,the distribution of ground subsidence funnel in the whole mining area is obtained using D-InSAR technology,and the deformation time series of the subsidence funnel is obtained using the small baseline subset(SBAS)technology,combined with the profile extracted across the deformation region,study the spatial and temporal evolution of mining surface deformations with small spatial scales and large deformation levels;Considering that the one-dimensional deformation of line of sight(LOS)cannot reflect the real surface deformation,a two-dimensional deformation time series estimation model integrating multiple orbital SAR data is derived.We obtained the 2D deformation time series in vertical and east-west direction of the Maizipo subsidence area using the ascending and descending Sentinel-1A/B images successfully;The uniform elastic half-space rectangular inversion model is used to invert the deformation mechanism of Maizipo subsidence area.The research results reveal the real coal mining deformation rule,and also provide data reference for ecological environment management and coal mine safety production in the subsidence area.