Research On Deformation Of High-filling Airport Facilities In Western Sichuan Using Time-series In Sar Techniques And Datasets

Western Sichuan is on the eastern edge of Qinghai-Tibet Plateau.It spans the first and second terrain steps in China.The mountain ranges have deep gorges and high peaks.The terrain is complex.China has built roads and railways on the first and second steps(such as the Qinghai-Tibet Highway and the Qinghai-Tibet Railway).However,for the vast geographical area,the existing transportation network does not meet the needs of economic development and national strategies.The development of these areas was adversely affected by limited transportation means.With reference to the development of the highway and railroad networks,the airport is a relatively convenient and economically variable option making the airport a“must-have”development in the region.Compared to the central and eastern regions of China,the developed airport in western Sichuan has the following characteristics.First,the rugged terrain causes the high filling and removing of earth materials for the runway.Second,the airport is in the earthquake-prone zone affected by constant quakes with high intensity.Third,the construction period of the airport is short.Thus,most foundations have the characteristics of the large deformation due to the low strength,high compressibility,large settlement,and slow drainage consolidation.The deformation after the completion is widespread.Therefore,it is important to identify and monitor the existing or potential deformation of the airports,as well as the deformation caused by earthquakes.Jiuzhai-Huanglong Airport is one representative of the high-filling airports in western Sichuan.During the construction,the amount of excavation reached3.09×10~7m~3.The filling amount exceeded 2.76×10~7m~3.The maximum filling depth reached 104m.The airport is in the northwest plateau triangle fault block.There are three fault zones including the Minjiang,Xueshan,and Huya faults.Major earthquakes occur frequently.The Wenchuan earthquake with the surface wave magnitude(Ms)of8.0 occurred on 12 May 2008.The epicenter was 206km away from the airport.The Jiuzhaigou earthquake happened on 8 August 2017.Its Ms was 7.0.The epicenter was only 48km away from the airport.Interferometric Synthetic Aperture Radar(InSAR)technique can accurately measure the three-dimensional spatial position.It can also provide spatially the sub-centimeter-accurate level of the surface deformation when multi-temporal observations are available.In this study,the differential interferometric synthetic aperture radar(DInSAR)and time-series small baseline subset(SBAS)InSAR methods coupled with,the JAXA ALOS/PALSAR and ESA/Sentinel-1 multi-temporal datasets were used to assess the deformation trend and long-term characteristics of Jiuzhai-Huanglong Airport and to evaluate the earthquake impact on the airport.One pair of SAR images before an earthquake,one pair of SAR images before and after the quake,and one pair of SAR images after the quake were used to investigate the surface deformation caused by each quake,respectively.The earthquake was very likely causing the negative displacement and six conspicuous areas with noticeable surface displacement along the line-of-sight(LOS)direction.To verify the observed deformation using the DInSAR technique,we then used the SBAS InSAR technique coupled with multiyear SAR images to monitor the long-term deformation characteristics of Jiuzhai-Huanglong Airport.As the comparison,the DInSAR and SBAS InSAR techniques were similarly applied to the surface deformation analyses of another high-filling and two other non-high-filling reference airports.The three airports experienced significant settlement after each strong earthquake.However,the deformation characteristics occurring at the Jiuzhai-Huanglong airport were not found at the non-high-filling airports.The earthquakes were mainly responsible for the negative displacement.The uneven displacement was highly correlated with the local geological settings.