Slope stability analysis of a plateau lake under strong earthquake impacts: a case study of Lake Sarez, Tajikistan

Strong earthquakes and complex terrain have produced unstable slopes around Sarez Lake, Tajikistan, threatening the Usoi Dam, downstream ecosystems and residents. Using Sentinel-1 images (September 2022–September 2024), we mapped surface deformation with SBAS-InSAR, classified two-dimensional deformation and integrated GNSS–InSAR data to analyze seismic anomalies. We inverted the focal mechanism using the Okada model, identified deformation zones via K-means and applied random forest–SHAP to assess environmental factors’ relative contributions and responses. The results show that horizontal motion dominates regional deformation, while seismic activity significantly induces slope instability. Three-dimensional deformation reveals slow lakeward movement of the Usoi Dam and slopes on both banks. The Mw 6.85 earthquake involved left-lateral strike-slip motion, with nearly E–W compression and N–S extension characterizing regional tectonic stress. Clustering places the Usoi Dam in a stable zone, with vertical subsidence dominating the left-bank slope and westward horizontal motion dominating the right-bank slope. Environmental statistics reveal marked topographic and geological differences among deformation zones. These findings provide quantitative evidence and remote-sensing support for deformation identification, environmental background analysis and safety risk assessment in alpine landslide-dammed lake regions.