Ground Subsidence Monitoring And Mechanism Analysis In Haikou Area Based On SBAS-InSAR Technology

Haikou is located in the northern part of Hainan Island.It is a key area for the construction of the Hainan Free Trade Zone.Ground subsidence is caused by natural factors and human behaviors,and it is a kind of geological disaster in which altitude is decreasing continuously.As the amount of groundwater mining increases year by year,the groundwater level continues to decline,the natural state of aquifers are destroyed,and ground subsidence disasters occur frequently,increasing the threat of seawater intrusion,back-irrigation and land salinization.Therefore,monitoring the settlement rate in Haikou area can ensure the stability and safety of the engineering buildings in the settlement area,which is of great significance to the sustainable development of the social economy and regional environment.Interferometric Synthetic Aperture Radar(InSAR)is the effective method of ground subsidence monitoring.Based on SBAS-InSAR technology,we used the Sentinel-1A satellite IW model data from 2015 to 2017 to acquire the average subsidence rate during that period.The leveling and PS-InSAR results are used to verify the accuracy and explore the mechanism of ground subsidence,Gain the following understanding and results:The spatial distribution law and settlement rate of land subsidence in Haikou area are studied systematically: the land subsidence area in Haikou is funnel-shaped and concentrated in the urban area of Haikou City,while in the suburb of Haikou City,the land subsidence amplitude is small and distributed in spot shape.In most areas,the average settlement rate is concentrated between-31.41~23mm/a.due to the influence of rock and soil thickness and lithology change,there is a certain degree of migration between the center of ground settlement funnel and the center of groundwater depression funnel.The study on the characteristics and time series of the surface deformation in Haikou area shows that there are not only periods of slow subsidence but also periods of slight uplift.From the point of view of shape variable level and duration,the main characteristics of surface deformation in the study area are subsidence,and the overall distribution of land subsidence is uneven.There are obvious differences in annual land subsidence rate.There are many obvious settlement centers,and the influence range of settlement leakage bucket and the settlement gradient of settlement center are increasing year by year.The mechanism of land subsidence in Haikou area is mainly as follows:(1)Fault activity and soil lithology are the internal factors leading to land subsidence;(2)Overexploitation of groundwater is the main factor inducing land subsidence;(3)A large number of development and construction and engineering disturbance are the human power to intensify land subsidence.