Multi-temporal InSAR analysis for assessment of earthquake precursory deformation

Ground deformation is a key parameter in interpreting precursory stress and strain patterns and provides valuable information for seismic studies. Interferometric Synthetic Aperture Radar (InSAR) is a robust technique capable of measuring such deformations with high precision. In this study, we applied Persistent Scatterer InSAR (PS-InSAR) and Small Baseline Subset InSAR (SBAS-InSAR) techniques to analyze surface deformation patterns prior to the M_W7.8 Türkiye earthquakes. A total of 40 Sentinel-1 SAR images in ascending mode (path-014) were used, covering the period from January 2022 to May 2023 with a 12-day repeat cycle, both before and after the February 6, 2023, seismic events. The area near the M_W7.8 earthquake epicenter exhibited deformation rates ranging from −42.9 mm/yr to +44.3 mm/yr based on PS-InSAR, while SBAS-InSAR indicated deformation in the range of −58.5 mm/yr to +47.7 mm/yr for the same location. The line-of-sight (LOS) deformation from the PS-SBAS merged analysis ranged from −43.4 mm/yr to +36.0 mm/yr. The integration of PS-InSAR and SBAS-InSAR provided greater reliability than single-method techniques. Several parameters were analyzed, including the PS-SBAS merged time series, wavelet power spectrum analysis of deformation values near the epicenter, and the first principal component (PC1) of wavelet coefficients, to identify precursory deformation before the earthquake. The PS-SBAS merged time series showed progressive phase decorrelation during the months preceding the event, indicating pre-seismic ground deformation. The wavelet power spectrum of the LOS deformation showed consistently high power from October 2022 to May 2023, suggesting abnormal pre-seismic activity. Furthermore, the monthly rate of change of wavelet PC1 revealed a declining trend prior to the earthquake, followed by an increase afterward. These observations point toward the potential for small-area precursory deformation monitoring using multi-temporal InSAR techniques.