Modeling and numerical simulation of volcanic mass movements and associated tsunamis at Stromboli (Aeolian archipelago, Tyrrhenian sea, Italy)

Tomaso Esposti Ongaro ^1* Matteo Cerminara ¹ Mattia De' Michieli Vitturi ¹ Alessandro Tadini ¹ Matteo Trolese ¹ Alessandro Fornaciai ¹ Luca Nannipieri ¹ Benedetta Calusi ^1,2 Jorge Macías ³ Manuel J Castro ³ Cipriano Escalante ³ Sergio Ortega Acosta ³ José Manuel González-Vida ³ Juan Francisco Rodriguez Galvez ^1,3

• ¹ National Institute of Geophysics and Volcanology (INGV), Pisa, Tuscany, Italy
• ² University of Florence, Florence, Tuscany, Italy
• ³ University of Malaga, Málaga, Andalusia, Spain

Mass movements at Stromboli volcano (Aeolian islands, Italy) have the capability of generating tsunamis, potentially affecting not only the island shores, but the whole Aeolian archipelago and the Southern Tyrrhenian sea. Such mass movements can be associated with subaerial and subaqueous slope instabilities accumulated on the Sciara del Fuoco, and with pyroclastic avalanches generated by the explosive activity. In this work, we present a wide set of volcanic mass movement scenarios and the subsequent tsunami generation, propagation and inundation on the Stromboli shores. Scenarios are produced by using a multilayer, depth-averaged nonhydrostatic numerical model able to simulate the dynamics of granular avalanches, their interaction with the sea, and the generation and propagation of the water waves. Five volumes ranging from 5 × 10^6 to 30 × 10^6 m^3 , and 10 vertical elevations from +322 m above to -584 m under the sea level are analyzed, to encompass the range hypothesized for the 2002 event at Stromboli. Densities of 1667, 2000 and 2500 kg/m^3 are explored. A total of 150 scenarios is here analyzed. Maps of the maximum wave height, arrival times, and water depth are stored for each scenario. Data include also waveforms at 11 sampling points, two of them corresponding to the two sensor-equipped buoys installed offshore. The most voluminous scenario predicts the largest maximum wave height of several tens of metres close to the Sciara del Fuoco, producing large inundation on the Stromboli shores. The shape of the proximal waves does not change with the volume of the granular mass, but is affected by its initial position. For a given volume, subaerial mass movements have the highest tsunamigenic potential, with the first crest being the highest one, and the responsible for most of the inundation. Moving to subaqueous positions, waveforms are characterized by a first, relatively small crest, followed by a trough and a higher second crest, responsible for the inundation. The effect of the density contrast on the wave elevation appear to be a second-order one. Simulation results are assembled in a publicly accessible database and made available for future hazard and risk assessment studies.