A Post-rockfall Event Analysis Based on 3D Point Cloud Investigation

This study investigates a rockfall event that occurred on May 18, 2025, in the northern sector of Mount Pellegrino (Palermo), within the Addaura district, a zone characterized by high susceptibility to slope instability due to complex struc-tural and geomorphological conditions. Traditional rockfall hazard assessments are commonly based on direct geomechanical surveys; however, these approaches are often constrained by limited accessibility and safety risks, especially in post-event scenarios. To address these limitations, this research adopts an indirect methodology based on high-resolution data acquired through Terrestrial Laser Scanning (TLS), which enables accurate three-dimensional reconstruction of the rock slope. By comparing pre-event 3D models (Google Earth) with post-event TLS point clouds, the detachment niche was successfully identified, and the vol-ume of the fallen block was estimated at approximately 67 m3. Additionally, the application of Discontinuity Set Extractor (DSE) algorithms allowed the identi-fication of four main joint systems governing rock mass stability. The analysis also detected 32 potentially unstable blocks on the slope, most of which have volumes below 20 m3. However, the studied event ranks among the largest, high-lighting the potential for high-magnitude failures. Overall, the results demonstrate the effectiveness of point cloud-based approaches and emphasize the importance of continuous monitoring and advanced modeling for improving rockfall hazard assessment.