The costal landslide from analogue experiments: perspectives and limitation

Understanding the triggering mechanism of coastal landslides (triggered and/or developed at air-water interface) and their evolution is fundamental to evaluate their hazard and, predicting the energy, the associated tsunami risk. The aim of this work is to verify the suitability of analogue modelling to understand the triggering mechanism and the evolution of landslide along the costal line. As a starting case study the Sciara del Fuoco (SdF), northwest flank of the volcanic island of Stromboli (Italy), was chosen. The analogue modelling technique has been proven to represent an useful tool to understand many geological processes, as it allows studying the progressive deformation, providing also useful indications about the role of distinct factors controlling the final deformation pattern. The models simulated at a first approximation the geological geometries observed at Stromboli, a composite volcano forming the northernmost island of the Aeolian Archipelago (Tyrrhenian Sea). The activity of Stromboli volcano is characterized by a persistent mild explosive activity at the summit craters sporadically interrupted by episodes of lava effusion and violent paroxysmal explosions as in 2002-2003 and in 2007. During the 2002 effusion a large landslide occurred on the SdF. The landslide caused a tsunami, which produced severe damages along the island shores. A series of analogue models was performed to investigate the influence of two different types of triggering mechanism and the behaviour of landslides both in air and air-water interface: 1) surface bulging due to the intrusion of a dike; 2) accumulation of material due to an uppermost landslide or due to opening of a new vent. The models, constructed in a Plexiglas tank, were scaled to the natural prototype following the geometrical, rheological, kinematical and dynamical similarities (e.g. Hubbert, 1937; Ramberg, 1981). The modelling material (Fontainbleau sand and rice) was sieved on a slope, inclination of which varing between 35° and 25°, depending on whether the simulated environment is subaerial or submarine, according to the inclination Average Sciara del Fuoco (Boldini et al. 2005; Chiocci et al., 2008). During models construction several difficulties came out as the difficulties to chose the suitable material for analogue models in the presence of water. Indeed the presence of water causes in the analogue materials a very fast capillary rising. In this work we propose some technical devices to minimize this limitations, such as impermeable barriers. References Boldini D., Wang F. W., Sassa K., Tommasi P., 2005. Mechanism of landslide causing the December 2002 tsunami at Stromboli volcano. Landslide: Risk Analysis and Sustainable Disaster Management, 173-180, Springer, New York. Chiocci F. L., Romagnoli C., Tommasi P., Bosman A., 2008. The Stromboli tsunamigenic submarine slide: Characteristic and possible failure mechanism. Journal of Geophysical research vol. 113, B 10102. Hubbert M.K., 1937. Theory of scale models as applied to the study of geologic structures. Geol. Soc. Am. Bull. 48, 1459-1520. Ramberg H., 1981. Gravity, deformation and the Earth’s crust in theory, experiments and geologic application, 2nd Edition. Academic, London, pp 1-452.