Instability Risk of Submarine Hydrate-Bearing Slopes Under Thermal Disturbances

Thermal disturbance can destabilize submarine hydrate-bearing sediments by reducing hydrate stability, promoting dissociation, weakening hydrate-derived cementation, and increasing excess pore pressure. This study develops a probabilistic framework coupling a one-dimensional thermal–hydrate evolution model with an infinite slope stability formulation. Hydrate system degradation is represented by a hydrate degradation risk index (RIhyd), whereas mechanical stability is evaluated using the minimum factor of safety (FSmin). The reference simulation places hydrate mainly at 140–200 m below the seafloor, with a peak initial saturation of approximately 0.45. Over 10 ka, the hydrate occurrence zone contracts by approximately 66.7%. The minimum factor of safety, FSmin, decreases from approximately 6.2, crosses the warning threshold of 1.30, and first reaches the critical threshold of 1.00 at approximately 4.6 ka after substantial hydrate system degradation. Monte Carlo simulations (=800) yield a terminal median FSmin of approximately 2.8 and a 5th–95th percentile range of 1.1–11.4; the corresponding median RIhyd is approximately 31. The terminal probabilities of warning and critical states are approximately 0.16 and 0.08, respectively. Sensitivity analysis identifies slope angle and total temperature rise as the principal controls on FSmin, while total temperature rise dominates the coupled risk response. The framework provides an uncertainty-aware screening tool for comparing hydrate degradation and slope stability responses.