Fatal debris avalanche on an anthropogenically disturbed, earthquake-perturbed slope during antecedent rainfall

Abstract On 8 December 2024, a fatal debris avalanche occurred on the Güngören hillslope in Artvin, northeastern Türkiye, the second deadly landslide on this anthropogenically modified slope since 3 April 2006. We integrate multi-source remote sensing and field observations to reconstruct pre-failure behavior, explore the roles of predisposing factors and short-term controls, and identify sectors susceptible to future failure. Historical 0.3 m MAXAR imagery, a post-event LiDAR DEM (9 December 2024), UAV-derived orthophoto and DSM, and Sentinel-1 InSAR time series from 2022 to 2024 support detailed geomorphic mapping and kinematic analysis. The hillslope exhibited persistent slow motion prior to failure, with mean annual line-of-sight velocities up to ~ 60 mm/year within and adjacent to the source area. The precipitation records show that the same slope experienced heavier daily totals in the last two years (e.g., ~ 150 mm and ~ 120 mm) without any failures, whereas the 8 December 2024 avalanche followed days with < 80 mm/day. We therefore interpret antecedent rainfall and internal hydrologic state during a moderately wet period as the proximate trigger, acting on a slope that had been progressively weakened over years to decades. Long-term anthropogenic modification from highway and quarry works, together with the earlier 2006 fatal landslide, indicates chronic susceptibility and is considered an important predisposing factor. An M w 4.7 earthquake on 15 November 2024, ~ 45 km from the site, produced low estimated ground motions (median PGA ≈ 0.006 g) and is best interpreted as a secondary predisposing factor that may have promoted crack growth and subtle hydrologic perturbations in an already conditioned slope, rather than as a stand-alone trigger. By combining InSAR, Red Relief Image Map analysis, and field mapping, we delineate three high-susceptibility sectors that warrant targeted monitoring and stabilization. This case illustrates how antecedent rainfall can govern failure timing in a humid, heavily modified setting where modest earthquake shaking and anthropogenic disturbance contribute to progressive slope weakening and residual hazard.