Regional identification of groundwater-induced land subsidence using integrated surface and subsurface observations

Groundwater-induced land subsidence is one of the most widespread geohazards associated with excessive groundwater exploitation, characterized by broad spatial extent and significant socio-economic impacts. However, conventional point-based monitoring techniques are unable to characterize the regional distribution of groundwater-induced subsidence. To address this limitation, this study integrates Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR), terrestrial water storage (TWS), and distributed fiber optic sensing (DFOS) to establish a regional-to-stratigraphic framework for identifying groundwater-induced land subsidence and interpreting its subsurface deformation characteristics. First, PS-InSAR was employed to derive the regional surface deformation patterns. Subsequently, the temporal correspondence between InSAR-derived deformation and regional TWS variations was quantified using Pearson correlation analysis to identify areas strongly associated with groundwater-induced subsidence. Finally, borehole DFOS observations were used to identify the dominant compressible strata responsible for subsurface deformation. A case study in Suzhou, China, shows that surface deformation exhibited a strong temporal correspondence with regional TWS during periods of intensive groundwater exploitation, whereas this correspondence weakened following groundwater recovery because of delayed consolidation within low-permeability strata. The borehole observations further indicate that the dominant deformation is concentrated within the Ad2 and Ad3 aquitards adjacent to the Af2 confined aquifer. Overall, the proposed framework links regional surface deformation with depth-dependent subsurface deformation, providing an effective approach for investigating groundwater-induced land subsidence and supporting groundwater management and geohazard assessment.