Monitoring of Surface Deformations in Geothermal Areas Using the InSAR Method: A Case Study from Denizli, Türkiye

Abstract. This study examines surface deformations in the Sarayköy geothermal field (Denizli, Türkiye) between 2020 and 2025 using Interferometric Synthetic Aperture Radar (InSAR) techniques. Sentinel-1 ascending and descending datasets were processed with the Small Baseline Subset (SBAS) method, and tropospheric corrections were applied to improve measurement reliability. By decomposing line-of-sight displacements into horizontal and vertical components, both the direction and intensity of ground movements were identified. The results reveal localized vertical subsidence at rates reaching up to −0.7 m/year, indicating significant ground instability in areas of intensive geothermal production. Time-series analyses further highlight seasonal deformation patterns, linked to extraction and reinjection cycles of geothermal fluids. These cycles influence not only the magnitude of subsidence but also the partial recovery of ground levels, underlining the sensitivity of the subsurface system to operational practices. From an applied perspective, such deformation poses risks to critical infrastructure, including pipelines, wells, and energy transmission facilities, as well as to surrounding communities. Continuous InSAR-based monitoring provides a cost-effective and scalable tool for identifying hazardous zones, improving reservoir management, and guiding mitigation strategies. Beyond local safety, these results contribute to broader discussions on sustainable geothermal energy production and national energy policy by demonstrating the need to balance energy generation with environmental and geotechnical stability. Integrating geodetic observations with operational data and geomechanical modeling will further enhance predictive capacity, supporting long-term resilience of Türkiye’s geothermal sector.