Risk Analysis Management of Volcanic Slopes in São Miguel Island, Azores

Abstract The Azores Archipelago is affected by several geohazards and natural disasters, including earthquakes, volcanic eruptions, and extreme meteorological events. This makes this region quite susceptible to landslides. To ensure the safety of natural slopes, it is vital to systematically assess and manage risk to propose measures to reduce the geotechnical risk of slope instability. Volcanic formations are unique in that they typically exhibit sizeable natural variability of lithological formations and heterogeneities, with significant variations in geometry. Therefore, the existing standard characterisation systems do not consider the heterogeneous nature and unique characteristics of volcanic formations. The instability of a slope was selected for the analysis in Porto Formoso. The hill is located on the north coast of the island of S. Miguel, in the Azores archipelago. From a geological point of view, the slope consists of a volcanic rocky mass of a trachytic nature, which is covered superiorly by an incoherent deposit of a pomitic nature. A 3D numerical model using the Material Point Method (MPM) was developed and applied to the site, including seismic action considering the Portuguese regulations. A slope risk analysis was analyzed, considering the MPM numerical results. Finally, conclusions are drawn.