The Marsili Seamount (Tyrrhenian Sea, Italy) is the largest submarine volcano in the Mediterranean Sea, located in the middle of the Marsili Basin, facing the Calabrian and Sicilian coasts on its eastern side, and the coasts of Sardinia on the opposite side. It has erupted in historical times, and its summit crest is affected by widespread hydrothermal activity. This study looks at mass failures taking place at different depths on the flanks of the volcano and estimates their associated tsunamigenic potential. Mass failure, tsunami generation, and propagation have been simulated by means of numerical models developed by the Tsunami Research Team of the University of Bologna. In all, we consider five cases. Of these, three scenarios, one regarding a very small detachment and two medium-sized ones (between 2 and 3 km³ failure volume), have been suggested as possible failure occurrences in the published literature on a morphological basis and involve the north-eastern and north-western sectors of the volcano. The two additional cases, one medium-sized and one extreme, intended as a possible worst-case scenario (volume 17.6 km³), affecting the eastern flank. Results indicate that small-volume failures are not able to produce significant tsunamis; medium-size failures can produce tsunamis which dangerously affect the coasts if their detachment occurs in shallow water, i.e., involves the volcano crest; and extreme volume failures have the potential to create disastrous tsunamis. In all the simulations, tsunami waves appear to reach the Aeolian Islands in around 10 min and the coasts of Calabria and Sicily in 20 min. This study highlights that there is a potential for dangerous tsunamis generation from collapses of the Marsili volcano and as a consequence a need to intensify research on its status and stability conditions. More broadly, this investigation should also be extended to the other volcanic seamounts of the Tyrrhenian Sea, since their eruptive style, evolution, and tsunamigenic potential are still poorly known.

The 1783 Scilla landslide–tsunami (Calabria, southern Italy) is a well-studied event that caused more than 1500 fatalities on the beaches close to the town. This paper complements a previous work that was based on numerical simulations and was focused on the very local effects of the tsunami in Scilla. In this study we extend the computational domain to cover a wider portion of western Calabria and northeastern Sicily, including the western side of the Straits of Messina. This investigation focuses on Capo Peloro area (the easternmost cape of Sicily), where the highest tsunami effects outside Scilla were reported. Important tsunami observations, such as the wave height reaching 6 m at Torre degli Inglesi and flooding that reached over 600 m inland, have been successfully modeled but only by means of a high-resolution (10 m) topo-bathymetric grid, since coarser grids were inadequate for the purpose. Interestingly, the inundation of the small lake of Pantano Piccolo could not be reproduced by using today's coastal morphology, since a coastal dune now acts as a barrier against tsunamis. Historical analysis suggests that this dune was not in place at the time of the tsunami occurred and that a ground depression extending from the lake to the northern coast is a remnant of an ancient channel that was used as a pathway in Roman times. The removal of such an obstacle and the remodeling of the coeval morphology allows the simulations to reproduce the tsunami penetration up to the lake, thus supporting the hypothesis that the 1783 tsunami entered the lake following the Roman channel track. A further result of this study is that the computed regional tsunami propagation pattern provides a useful hint for assessing tsunami hazards in the Straits of Messina area, which is one of the most exposed areas to tsunami threats in Italy and in the Mediterranean Sea overall.

The adoption of Nature-Based Solutions (NBSs) represents a novel means to mitigate natural hazards. In the framework of the OPERANDUM project, this study introduces a methodology to assess the efficiency of the NBSs and a series of Open-Air Laboratories (OALs) regarded as a proof-of-concept for the wider uptake of NBSs. The OALs are located in Finland, Greece, UK, Italy, and Ireland. The methodology is based on a wide modeling activity, incorporated in the context of future climate scenarios. Herein, we present a series of models’ chains able to estimate the efficiency of the NBSs. While the presented models are mainly well-established, their coupling represents a first fundamental step in the study of the long-term efficacy and impact of the NBSs. In the selected sites, NBSs are utilized to cope with distinct natural hazards: floods, droughts, landslides, salt intrusion, and nutrient and sediment loading. The study of the efficacy of NBSs to mitigate these hazards belongs to a series of works devoted to the implementation of NBSs for environmental purposes. Our findings prove that land management plays a crucial role in the process. Specifically, the selected NBSs include intensive forestry; the conversion of urban areas to grassland; dunes; marine seagrass; water retention ponds; live cribwalls; and high-density plantations of woody vegetation and deep-rooted herbaceous vegetation. The management of natural resources should eventually consider the effect of NBSs on urban and rural areas, as their employment is becoming widespread.

Ischia Island has been repeatedly affected by mass collapses, which are mainly caused by the steepness of the main peak (Mt Epomeo) and by phenomena related to its volcanic activity. The most relevant cases of mass failure studied in the literature and postulated to be tsunamigenic cover a wide spectrum of sizes, from sector collapse to small-volume mass transports. Tsunamis generated by landslides in Ischia may affect the coast of the Campania mainland, including the Gulf of Naples. The focus of this work is an evaluation of the pattern of the maximum tsunami energy. To this purpose, we perform a series of numerical simulations by moving the same landslide source in different hypothetical positions around the island. The landslide dynamics are computed through the code UBO-BLOCK, and the tsunami propagation by employing the code UBO-TSUFD, both developed in-house. The final goal is to characterize the coastal areas of the Campania mainland most exposed to tsunami attack from Ischia sources. It is found that the position of the landslide deeply influences the distribution of the tsunami elevation in the coastal stretch north of the Procida Mt, while, remarkably, it is irrelevant inside the Gulf of Naples where the bathymetric effect prevails.

In this study, we present a new 2D numerical model, UBO-Inter, able to simulate the motion of a body sliding down a generic surface. Such a body is represented as a mechanical system of a finite number of point masses, where the points can be viewed as the projections on the sliding surface of the centers of mass of the elements which the system is discretized into. The masses are strictly adherent to the surface and interact with the neighbor masses through internal forces. The entire system can be seen as a 2D irregular grid where the masses occupy the nodes of the grid, and each grid side connects a pair of interacting masses. The external forces acting on the masses are gravity, which is the driving force, the reaction force of the sliding surface, the basal friction and the drag exerted by the environmental fluid (typically water, for a slide moving partially or totally underwater). The system is governed by a set of differential equations that are solved through a fourth-order Runge–Kutta scheme. After providing the formulation of the problem and a simple example admitting an exact solution that serves to illustrate the internal forces, we validate the model on the 1783 Scilla (Calabria region, Italy) landslide, that is a well-known catastrophic event that caused a lethal tsunami killing more than 1500 people. This case has been already widely studied and thus can be used as a benchmark for landslide models. The outputs of the model UBO-Inter in terms of time-histories of point-mass velocities, run-out and final deposit, are found to be in agreement with observations and with results published in literature and obtained through different numerical techniques.

In this study, we introduce a system of differential equations describing the motion of a single point mass or of two interacting point masses on a surface, that is solved by a fourth-order explicit Runge–Kutta (RK4) scheme. The forces acting on the masses are gravity, the reaction force of the surface, friction, and, in case of two masses, their mutual interaction force. This latter is introduced by imposing that the geometrical distance between the coupled masses is constant. The solution is computed under the assumption that the point masses strictly slide on the surface, without leaping or rolling. To avoid complications stemming from numerical errors related to real topographies that are only known over discrete grids, we restrict our attention to simulations on analytical continuous surfaces. This study sets the basis for a generalization to more complex systems of masses, such as chains or matrices of blocks that are often used to model complex processes such as landslides and rockfalls. The results shown in this paper provide a background for a companion paper in which the system of equations is generalized, and different geometries are presented.