基于SBAS-InSAR技术的围填海区域地面沉降监测

Land Subsidence Monitoring in Reclamation Area based on SBAS-InSAR Technique

以围填海活动为代表的沿海快速城市化过程,是引起地面沉降的重要影响因素之一。研究聚焦沿海围填海活动热点区域广州市南沙区,使用2015年6月~2018年4月共34景Sentinel-1数据,应用SBAS-InSAR技术,揭示了南沙区在研究时段内地面沉降的时空变化格局及演变特征。结果表明:(1)南沙区整体呈现持续沉降的趋势,沉降速率分化严重,平均沉降速率达到3.2 mm/a,圈层分析法显示中心圈层平均沉降速率为2.6 mm/a,最外层平均沉降速率为26.8 mm/a;(2)该区地面沉降在空间上呈现出异质性,主要分布在东部和南部,其中南部万顷沙、龙穴岛地面沉降最为严重,最大年沉降速率达到72.2 mm/a,在2015年6月~9月还出现地面沉降回弹现象,可能是台风天气带来季节性强降水变化影响。(3)基于不同极化方式的Sentinel-1数据进行交叉验证,VV极化、VH极化监测结果平均值分别为2.09 mm和1.01 mm,均方根误差分别为1.12 mm和2.65 mm。结果表明:SBAS-InSAR技术在提取围填海区域的地面沉降信息方面是有效可靠的,能更好地为监测沿海地区的地面沉降情况提供科学依据。

The reclamation activities of rapid urbanization process is a significant factor to cause land subsidence.This study has focused on land subsidence along with the coastal reclamation activity over Nansha district in Guangzhou city.A total of 34 Synthetic Aperture Radar(SAR)images acquired by Sentinel1 between June 6,2015 and April 2018 are used to monitor the surface deformation and find the spatial and temporal variations of land subsidence by employing a small baseline subset Interferometric Synthetic Aperture Radar(SBAS-InSAR)technique.The results show that:(1)the Nansha district shows a trend of continuous subsidence of the whole.,but the land subsidence rate is highly polarization.The average settlement rate is 3.2 mm/a,while the center layer and the outermost layer are 2.6 mm/a and 26.8 mm/a,respectively;(2)The land subsidence shows spatial heterogeneity.The mainly distributed in the east and south,which Wanqingsha area and Longxue-Island in the south have the most serious land subsidence,with the maximum annual subsidence rate exceeding 60 mm/a(up to-68.9 mm/a).And the land subsidence rebound phenomenon also is found from June to September,2015.(3)Cross-validation was conducted with different Sentinel-1 polarization modes.The average values of VV polarization and VH polarization monitoring results were 2.09 mm and 1.01 mm,respectively,and the root-mean-square errors are 1.12 mm and 2.65 mm,respectively.The results show that SBAS-InSAR technology is effective and reliable in extracting land subsidence information in the reclamation area and provides scientific basis for better monitoring land subsidence in coastal areas.