Co-seismic surface deformation and Aftershock analysis of the M 7.3, 17 Dec 2024 earthquake near Port Vila, Efate Island, Vanuatu: Insights from InSAR line of sight, coherence analysis & validation through high resolution satellite imagery

M7.3 earthquake on 17 December 2024 occurred 25 Km offshore of Efate Island, Vanuatu, a seismically active region. This study analyses co-seismic ground deformation using Sentinel-1A SAR data and Differential Interferometric SAR (DInSAR) to measure line-of-sight (LOS) displacement, with special emphasis on coherence loss to identify regions of surface deformation.Ground truthing was performed using ground deformation points and high-resolution Pleiades and WorldView-3 imagery from UNOSAT rapid damage assessment report. Strong correlation between ground deformation and coherence loss confirmed its reliability in capturing surface instability and building damage.The line-of-sight displacement maps from November 2024 to February 2025 demonstrate variation in upliftment (upto + 0.084 meters) and subsidence (down to − 0.067 meters) values. Fluctuations in displacement rates were associated with aftershock activity. The aftershock analysis revealed that more than 50 aftershocks occurred in December 2024 following the mainshock, and the frequency of aftershocks gradually reduced through January and February 2025. The temporal analysis explained the importance of aftershocks in co- and post- seismic ground displacement analysis.These outcomes demonstrate the important role of combined geodetic and seismic analyses for assessing the dynamic seismic hazards experienced by the Vanuatu region and offers critical insights into the landscape adjustments following large earthquake events. Continues monitoring and in-depth aftershock analyses are important for reliable disaster risk reduction and infrastructure resilience planning.