Land subsidence and uplift surveying by synthetic aperture radar interferometry in Lianjiang plain

Abstract

In order to investigate the distribution of land subsidence in the Lianjiang Plain, the interferometric point target analysis (IPTA) method has been carried out with RADARSAT-2 data in this work. It was found that large-scale land uplift occurred in Puning City and Shantou City, and the maximum rebound velocity exceeded 100 mm/a in 2019. Then, the Sentinel-1 data collected from June 2015 to November 2019 were used to carry out a long-term sequence inversion of the ground rebound zone and further verify the RADARSAT-2 monitoring results. The results of both kinds of data show the similar distribution characteristics of the two uplift zones. After the preliminary analysis of interferometric synthetic aperture radar (InSAR) results, geological data, and local government reports, the major factor causing land subsidence and uplift was concluded to be the change in groundwater level. The thick Quaternary strata and the compressible/expandable soil layers provide conditions for rapid subsidence and uplift. Also, the south edge of each uplift zone is limited by the WNW-trending Puning-Tianxin fault, where the land deformation is accompanied by ground fissures.