Operational radar monitoring of crater rim failure at Stromboli volcano (Italy)

This work presents the operational application of the Ground-Based Interferometric Synthetic Aperture Radar (GBInSAR) data to anticipate the collapse of incandescent volcanic material deposited on crater rims, a poorly understood process that can trigger glowing rock avalanches, often referred to as deposit-derived pyroclastic density currents (PDCs). The results show that this method effectively identifies anomalous periods, assesses the level of instability, and provides timely anticipation of any observed failures. During the 2024 eruption at Stromboli, the system detected a progressive increase in instability corresponding to increased eruptive activity, and provided early warnings of major crater rim collapses. These failures are interpreted as being caused by magma thrust, driven by lava densification and conduit pressurisation by ascending low-density magma. Although effective, the method has limitations in estimating collapse volumes, mainly due to its reliance on empirical area-volume relationships and the challenge of distinguishing between single and multiple failure events. Refinements incorporating improved morphometric data and stability models could improve its predictive capability. GBInSAR provides high-resolution deformation data in real time, enabling effective early warning systems. Since 2003, this approach has proven successful at Stromboli and could be adapted to other active volcanic environments, providing a valuable tool for assessing the instability of hazardous volcaniclastic accumulations and contributing to PDC-related risk mitigation.