Subsidence Monitoring Of Sichuan Mountain Area Based On Time Series InSAR Technology

Sichuan Province was located in the “Seismic Belt of Sichuan Province,and earthquake disasters occur frequently here.The “Wenchuan Earthquake” in 2008 and the“Jiuzhaigou Earthquake” in 2017 were few of the recent noteworthy earthquakes occurring at this place.Meanwhile,the frequent occurrence of earthquakes and various faults have also induced the geological disasters such as landslides,collapses and mudslides,which pose a great threat to the safety of human beings.In the Aba Prefecture that encompasses numerous mountain ranges,and different geological and natural environments,geological disasters such as landslides have higher occurrence and great destructive power,and they have complex formation mechanisms with many induced factors.This makes the Aba Prefecture as one of the regions with great protection in China.In the process of landslide hazard monitoring,traditional measurement techniques have short observation and periods and can only be monitored for points.Comparatively,InSAR technology has characteristics of high resolution,wide coverage,high precision and all-wether.It is not affected by the weather and improves safety while completing regional deformation monitoring,which makes InSAR widely used in monitoring of landslide.Based on this factor,this paper selects Mao Xian and Jiuzhaigou as the research area.The main research content was the monitoring and detection of the landslide displacement based on the Time-Series InSAR(TS-InSAR)method,which provides a reliable data and theoretical support finding of the hidden danger areas and engineering prevention.The experimental plan and results were as follows:(1)Based on the Small Baseline Subset(SBAS)technology,the 21-field ALOS-1satellite data covering the Mao Xian County and surrounding areas was processed.The average rate of displacement and cumulative deformation in this study area was investigated from 2006 to 2011.In addition,the average displacement rate result was compared with historical remote sensing image data.The result showed that the area of sinking in the county of Mao Xian is consistent with the collapse range of the house affected by the landslide disaster in the remote sensing image.At the same time,theresults of time-series analysis of bridge collapse and road blocking points indicated that,the deformation rate around Wenchuan Earthquake is greater than other time,and the cumulative displacement among 7 months can reach 100 mm.(2)The post-earthquake displacement monitoring of Jiuzhaigou was carried out using 25 Sentinel-1A data in the period August 2017 to July 2018.Meanwhile,the TS-InSAR processing results were obtained and were in good agreement on comparing with the GPS results,and the error of each point is less than 7mm.This ensured the accuracy of the InSAR results.Additionally,based on the TS-InSAR results,the time series analysis of the study area was carried out.The distuibution of the time series deformation of the area was analyzed,and the study area was divided into four areas with different sinking conditions.Simultaneously,an area of about 1km2 with maximum msinking rate of 120mm/yr was found.From the result of time series deformation,it is analyzed as the hidden danger point of landslide hazard,which provided a prior basis for the high-lever investigation of landslide disaster.