Benefits and limitations of InSAR-based monitoring of ground movements above cavern underground gas storage sites: a Polish case study

Abstract

Ground displacement monitoring is a key aspect of assessing the impacts of underground gas storage (UGS). Conventional approaches are based on geodetic methods that, while providing high accuracy, are limited in spatial coverage and temporal resolution. This study assesses the suitability of synthetic aperture radar interferometry (InSAR) as a complement to standard ground displacement monitoring and identifies a method with sufficient accuracy to assess ground displacement conditions and facility safety. A comparative analysis was conducted using European Ground Motion Service (EGMS) data and independently derived Sentinel-1-based time series generated with the small baseline subset (SBAS) and persistent scatterer InSAR (PSI) methods. The analysis of a cavern UGS facility located in northern Poland spanned a five-year period from 2019 to 2023 and included error analysis and significance testing of differences between the methods. Observed displacement rates across the study area ranged from −4.3 mm/year for the SBAS method to −0.4 mm/year for PSI. Although the absolute values of the estimated velocities differed among the methods, the differences between the modeled deformation rates were statistically insignificant. The results confirm that InSAR can supplement geodetic monitoring and help investigate seasonal ground deformations associated with gas injection and withdrawal cycles as well as environmental processes, capturing patterns that discrete geodetic measurements may miss.