Kinematic and structural analysis of the East Anatolian Fault System using InSAR and gravity: Insights from the 2023 earthquakes

On February 6, 2023, a catastrophic sequence of earthquakes struck southeastern Türkiye and northern Syria along the East Anatolian Fault System (EAFS), culminating in one of the most destructive seismic episodes in recent decades. This study examined the kinematic behavior, structural segmentation, and tectonic dynamics of the EAFS and its northern splay, the Sürgü-Çardak Fault (SCF). To achieve this, we adopted an integrated geodetic-geophysical approach that integrates small baseline subset interferometric synthetic aperture radar (SBAS-InSAR)–derived surface displacement measurements with gravity-based geophysical interpretations. A time-series analysis of Sentinel-1A acquisitions spanning 2018–2023 was conducted to assess deformation processes along the fault system. The SBAS-InSAR processing enabled us to monitor surface displacement associated with fault activity in regions lacking continuous global navigational satellite system coverage along the extent of the fault. In parallel, gravity data were analyzed to delineate subsurface structural boundaries by characterizing lateral gradients. Fourteen line-of-sight displacement profiles, ten across the EAFS and four across the SCF, revealed pronounced spatial heterogeneity in deformation patterns, which may indicate the coexistence of a partially locked and aseismically creeping fault segment. The mainshock may have nucleated within fault zones that were relatively locked and affected by elevated stress accumulation, where deformation patterns are likely to differ from those observed in other parts of the fault system. The integration of surface displacement inferred from InSAR with structural heterogeneities derived from gravity gradients supports a revised segmentation framework for the EAFS, comprising five distinct structural segments. This integrative geophysical approach advances our understanding of fault system architecture and rupture dynamics, with direct implications for probabilistic seismic hazard assessment. The findings underscore the critical importance of implementing continuous SAR-based monitoring strategies in tectonically active regions to enhance resilience and inform long-term risk mitigation efforts.