Monitoring land subsidence with the combination of persistent scatterer interferometry techniques and distributed fiber optic sensing techniques: a case study in Suzhou, China

Land subsidence is a global geo-hazard caused by various natural and human factors, and it directly threatens the safety of the environment and infrastructures. Investigating the mechanism of land subsidence is becoming more and more important. In this paper, we use the persistent scatterer interferometry (PSI) technique combining the distributed fiber optic sensing (DFOS) technique to detect the spatial–temporal distributions of land subsidence and investigate the stratum deformation characteristics in Shengze, Suzhou. By analyzing Sentinel-1A date between 2017 and 2019 with the PSI technique and the deformation date derived by the DFOS technique, we conclude that the land surface deformations are mostly affected by the transitional exploitation of groundwater. The average line-of-sight (LOS) deformation rate is mostly concentrated in − 3 to 2.2 mm/yr, and a maximum subsidence rate of up to − 16.9 mm/yr is observed in four industrial areas. Meanwhile, the DFOS-derived results reveal that the compression strata are mostly concentrated in 41.2–137.9 m depth, which is closely associated with the pore water pressure in the second confined aquifer. And it also reveals that the groundwater over-exploitation may be the significant triggering factor of the subsidence in the study area. The InSAR-derived results are also evaluated by the deformation time series obtained by the DFOS technique. The combination of those two new sensing and monitoring technologies enables us to highlight the large deformation area and reveal the mechanism of its subsidence, which is conducive to urban development, disaster risk management, and rational exploitation and management of groundwater in Suzhou, China.