Climate change has increased the frequency of widespread landslide events over large areas, thereby highlighting the growing need for reliable regional-scale slope hazard assessments. Scoops 3D (Reid et al., 2015), developed by the U.S. Geological Survey, is a widely used open-source software for slope stability analysis based on a three-dimensional Limit Equilibrium Method (LEM) employing spherical slip surfaces. However, this assumption can limit analytical accuracy when applied to complex terrains, particularly in regional-scale analyses where diverse failure mechanisms may coexist. To overcome this limitation, this study introduces ellipsoidal slip surfaces, which provide greater geometric flexibility and enable a more realistic representation of complex failure shapes. In addition, Particle Swarm Optimization (PSO) is employed to efficiently identify critical slip surfaces within the expanded parameter space. Numerical experiments using real terrain data demonstrate that the use of ellipsoidal slip surfaces leads to improved accuracy, while PSO effectively mitigates the associated increase in computational cost and maintains a low error in the factor of safety (FOS).

Regional-scale,slope stability analysis