Rockfall hazard threatening archaeological sites in seismically active volcanic areas: the example of Baia Castle (Campi Flegrei)

The Baia Castle cliff, situated in the western sector of the Gulf of Naples (within the Campi Flegrei caldera, southern Italy), is subject to ongoing geomorphological processes and cliff retreat, which threaten both the archaeological heritage and coastal infrastructure. Additionally, the periodic uplift and subsidence activity, known as bradyseism, of the caldera is often accompanied by seismic events, which, as a secondary effect, can trigger rockfalls.

This study presents a comprehensive assessment of rock mass instability at the Baia Castle cliff through high-resolution UAV-based photogrammetry, semi-automatic point cloud analysis, and traditional field surveys. The combination of remote and in-situ methods, integrated with laboratory geomechanical analysis, enabled performing a detailed geostructural characterisation and kinematic analysis of the potential failure mechanisms affecting the tuffaceous cliff. Additionally, successive drone-derived DEMs before and after the June 2025 rockfalls that occurred in the area were compared to quantify the mobilised volumes and the cliff retreat. Furthermore, the failure events of 2025 were compared with the geostructural results preceding the rockfall and with the seismic site response analysis, to investigate any potential predisposing factors that localised the rockfall detachment.