Spatiotemporal Evaluation of Pre-Seismic Deformation Patterns: The Case of Northern Thessaly, Greece

Abstract. In recent years, the use of satellite-based Interferometric Synthetic Aperture Radar (InSAR) has gained increasing attention for exploring potential precursory ground deformation related to earthquakes. Among the emerging resources, the European Ground Motion Service (EGMS) provides a unique opportunity for regional-scale, long-term deformation monitoring through freely accessible datasets. This study investigates the potential of EGMS products to detect pre-seismic deformation patterns preceding the 2021 Mw 6.3 Thessaly earthquake in northern Greece. The analysis utilized the vertical (Up-Down) and horizontal (East-West) components of EGMS Ortho deformation time series, spanning January 2016 to December 2021. After removing seasonal effects, the time series were divided into two phases: a long-term “Before” phase and a short-term “After” phase covering the final year prior to the mainshock. A differential velocity analysis was applied to evaluate changes in the spatial deformation field over time. Results revealed a clear and localized acceleration in both vertical and horizontal components within a 15–20 km radius around the epicentre, occurring specifically in the year leading up to the earthquake. These changes are interpreted as potential indicators of fault zone activation, possibly related to aseismic slip or fluid-driven processes. The findings highlight the value of EGMS products and multi-temporal InSAR techniques in contributing to the ongoing search for reliable earthquake precursor signals, reinforcing their role in seismic hazard research and early warning strategies.