| Ground subsidence is a slow and cumulative geological disaster.Coastal cities are susceptible to surface deformation due to both seawater erosion and man-made surface disturbance,which endangers local production and life safety.Therefore,it is essential to real-time monitor the surface subsidence in coastal cities.Although the traditional surface settlement monitoring method is highly accurate,the observation period is long and laborintensive.The In SAR technology developed in recent years has the advantages of wide monitoring range,high monitoring accuracy,and all-weather all-day,overcoming the shortcomings of traditional monitoring methods,and is widely used to monitor small deformations and geological hazards over a long period of time and on a large scale.This paper focus on the reliability of PS-In SAR and SBAS-In SAR techniques in monitoring surface deformation in coastal cities and their potential ground settlement influences.The main research contents are as follows:(1)Using Sentinel-1A elevated orbit imagery with 35 views covering Caofeidian area,the surface deformation of the study area was monitored by PS-In SAR and SBAS-In SAR techniques,combined with high-precision DEM data,and selected optimal parameters through several experiments.The deformation rate and distribution of Caofeidian area for the period from February 2019 to December 2021 were obtained,and the results get by the two methods were compared and validated to explore the reliability of In SAR technology for surface monitoring in coastal areas.The results show that the subsidence area in Caofeidian District is large,and the subsidence is mainly concentrated in Binhai Town,Wenfeng Steel Yard and Tangshan Bay Eco-city,and forms a continuous trend.By analyzing the time-series deformation characteristics of Caofeidian industrial zone,the result found that the surface disturbance of the industrial zone has some influence on its subsidence.(2)For the surface deformation problem of Pudong New Area,the SBAS-In SAR technique,which fuses highly coherent PS points,is used to invert the deformation information of Pudong New Area based on Sentinel-1A data.The results show that the maximum settlement rate of the surface in the study area is-32.105 mm/a during the monitoring period.Analyzing the characteristics of surface deformation in time and space in Pudong New Area,it is show that most of the areas in the study area are stable,local subsidence is serious,a large area of subsidence is monitored in the central area,and uneven subsidence exists in the reclamation area,and there is a trend of more and more serious subsidence from west to east.In order to further elucidate the settlement mechanism in the reclaimed area of Pudong New Area,a detailed analysis of the surface deformation of the reclaimed area is focused on the temporal variation.Finally,the results obtained from this paper are compared with the PS-In SAR method,the results found that the two techniques have approximately the same performance in monitoring deformation,which demonstrates the reliability and rationality of the method used in this paper.(3)Using the multi-scale geographically weighted regression model to analyze the potential influencers in Pudong New Area.The results show that the rate of ground deformation in Pudong New Area has the strongest correlation with the density of buildings,the distance from the river has a negative influence on ground settlement,and the altitude has a positive influence on the population density.It was also found that the intensity and scale of action of different influencing factors differed in different areas,the building density and total settlement much higher than the scale of action of other variables,while distance from the river had the second highest scale of action.Therefore,the spatial differences and scale effects of different influencing factors can be taken into account when formulating ground subsidence hazard prevention and control policies,thus making the decision more targeted. |
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