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Hindcasted wind and wave data, available on a coarse resolution global grid (Copernicus ERA5 dataset), are downscaled by means of the numerical model SWAN (simulating waves in the nearshore) to produce time series of wave conditions at a high resolution along the Italian coasts in the central Tyrrhenian Sea. In order to achieve the proper spatial resolution along the coast, the finite element version of the model is used. Wave data time series at the ERA5 grid are used to specify boundary conditions for the wave model at the offshore sides of the computational domain. The wind field is fed to the model to account for local wave generation. The modeled sea states are compared against the multiple wave records available in the area, in order to calibrate and validate the model. The model results are in quite good agreement with direct measurements, both in terms of wave climate and wave extremes. The results show that using the present modeling chain, it is possible to build a reliable nearshore wave parameters database with high space resolution. Such a database, once prepared for coastal areas, possibly at the national level, can be of high value for many engineering activities related to coastal area management, and can be useful to provide fundamental information for the development of operational coastal services.

Submarine landslides can pose serious tsunami hazard to coastal communities. However, performing a comprehensive landslide tsunami hazard assessment for a given area is in general difficult in view of the large uncertainty associated with tsunamigenic source parameters, which are often only approximately defined, based on estimates of the landslide geometry, slide material properties, and resulting kinematics. Therefore, a Probabilistic Tsunami Hazard Analysis (PTHA) should be performed by considering a large number of cases, which is computationally demanding. Here, we present an efficient model based on solving the linear Mild-Slope Equation with a time-dependent source term representing the seafloor motion. This approach allows carrying out many computations, for a large number of landslide scenarios, in a Monte Carlo (MC) approach framework, at a reduced computational cost compared to other available methods, while still providing physically accurate simulations of most landslide tsunami generation and propagation processes. To further speed-up the MC simulations, a database of elementary solutions is first developed, for many landslide sources of unit amplitude motion over a small seafloor area within the possible landslide footprint. For each unit source, the resulting tsunami elevations are computed and saved at many locations of interest. In the MC simulations, a large number of landslide scenarios are defined by randomly selecting slide parameters within their statistical distributions and each is then simulated for their specific bottom motion using a linear combination of the pre-computed unit sources. Hence, each resulting tsunami is quickly computed at the locations of interest by linear superposition. The paper presents the model validation against two tests cases and describes its novel methodology to perform multiple landslide tsunami scenarios.

Perforated multichamber caisson breakwaters are widely used for deep water harbour protection from waves, causing a partial dissipation of wave energy, hence reducing wave reflection. The innovative patented geometry presented in this paper, the ARPEC, is an Anti Reflection PErmeable Caisson breakwater that allows a significant wave energy dissipation and a hydraulic connection between the sea side and the port side by means of a labyrinthine pattern of offset openings in all external and internal walls. The hydraulic response of this innovative structure is evaluated by means of both 2D physical and numerical models. It is shown that, when compared with traditional impermeable perforated caissons, the marginal increase of wave transmission ( C T = H T / H I in the approximate range of 0.1–0.2, varying with wave period) is compensated by a slight reduction of wave reflection ( C R = H R / H I in the approximate range of 0.3–0.6, varying with wave period) and by an enhanced water circulation in the sheltered basin, which is beneficial for flushing of microtidal harbours.

Tsunamigenic earthquakes trigger pressure waves in the ocean, given the weak compressibility of the sea water. For particular conditions, a resonant behavior of the water layer can occur, which influences the energy transfer from the sea-bed motion to the ocean. In this paper, the resonance conditions are explained and analyzed, focusing on the hydro-acoustic waves in the proximity of the earthquake area. A preliminary estimation of the generation parameters (sea-bed rising time, velocity) is given, by means of parametric numerical simulations for simplified conditions. The results confirm the importance of measuring, modeling, and interpreting such waves for tsunami early detection and warning.

The paper investigates on the hydro-acoustic waves propagation caused by the underwater earthquake, occurred on 6 February 2012, between the Negros and Cebu islands, in the Philippines. Hydro-acoustic waves are pressure waves that propagate at the sound celerity in water. These waves can be triggered by the sudden vertical sea-bed movement, due to underwater earthquakes. The results of three dimensional numerical simulations, which solve the wave equation in a weakly compressible sea water domain are presented. The hydro-acoustic signal is compared to an underwater acoustic signal recorded during the event by a scuba diver, who was about 12 km far from the earthquake epicenter.

This paper presents a new methodology to reproduce the interaction between waves and floating objects over mildly variable bathymetry. The elliptic mild slope equation solves the fluid velocity potential over a domain, which does not include the near field around each object. The waves scattered by the floating bodies are considered by means of boundary conditions at the edges of the near field areas. The coefficients of these boundary conditions are obtained nesting the solution of a near field three dimensional solver with the elliptic model solution. Comparison with a 3D numerical model, which solves the potential flow field over the whole domain, is used to validate the proposed approach. An example of application to reproduce the wave field around an array of wave energy converters is presented.

Submarine landslides can pose serious tsunami hazard to coastal communities, occurring frequently near the coast itself. The properties of the tsunami and the consequent inundation depend on many factors, such as the geometry, the rheology and the kinematic of the landslide and the local bathymetry. However, when evaluating the risk related to landslide tsunamis, it is very difficult to accurately predict all of the above mentioned parameters. It is therefore useful to carry out many simulations of tsunami generation and propagation, with reference to different landslide scenarios, in order to deal with such uncertainties (see for example the probabilistic approach by Grilli et al. 2009). Accurate computations of landslide tsunami generation, propagation, and inundation, however, is computationally expensive, thus limiting the possible maximum number of scenarios. To partially overcome this difficulty, in the present research, a numerical model is proposed that can efficiently compute a large number of tsunami simulations triggered by different landslides. The main goal is to provide a numerical tool that can be used in a Monte Carlo approach framework. Following the study by Ward (2001), we propose a methodology taking advantage of the linear superposition of elementary tsunami solutions.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/uYOvdsutmBw

An innovative caisson breakwater geometry (patent pending) named "ARPEC" (Anti Reflective PErmeable Caisson) includes openings at all external and internal walls and at lateral (cross) ones, yet in a staggered pattern, to provide a labyrinthian hydraulic communication between the open sea and the internal waters. The complex sinuous water-flow within the consecutive permeable chambers thus favors wave energy dissipation as well as port water flushing and quality, with very low reflection and transmission coefficients. 2D lab model tests demonstrate the system effectiveness.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/PaUsinYO-Zo

This paper collects the results of several new 2D physical model tests on wave interaction with rubble mound breakwaters. The wave forces on the crown wall are analyzed in detail, showing their dependence on the tested geometric and hydraulic configurations. The database for this analysis is obtained from three models of different rubble mound breakwaters reproduced at the new smallmedium scale wave flume of the Department of Engineering of Roma Tre University, for a total of 184 random wave tests. The paper aims at improving the prediction of wave forces on the crown wall, proposing new empirical formulae and enhancing the model tests database of wave forces and overtopping discharges.

In this paper, we test a method for forecasting in real-time the properties of offshore propagating tsunami waves generated by landslides, with the aim of supporting tsunami early warning systems. The method uses an inversion procedure, that takes input data measurements of water surface elevation at a point close to the tsunamigenic source. The measurements are used to correct the results of pre-computed numerical simulations, reproducing the wave field induced by different landslide scenarios. The accuracy of the method is evaluated using the results of laboratory experiments, aimed at studying tsunamis generated by landslides sliding along the flank of a circular shoreline island. The paper investigates what the optimal position is of where to measure the tsunamis, what the effects are, the accuracy of the results, and of uncertainties on the landslide scenarios. Finally, the method is successfully tested using partial input time series, simulating the behaviour of the system in real-time during the tsunami event when forecasts are updated, as the measurements become available.

A numerical model based on the mild slope equation, suitable to reproduce the propagation of small amplitude tsunamis in the far field, is extended to reproduce the generation and the propagation of waves generated by landslides. The wave generation is modeled through a forcing term included in the field equation, which reproduces the effects of the movement of a submerged landslide on the fluid. The measurements of three dimensional laboratory experiments, which simulate tsunamis generated by landslide sliding along the flank of a conical island, are compared with the theoretical calculation results. The present approach is also compared with the similar method of Tinti et al. (2006) used for the generation of these waves in depth integrated model, and the different behavior when using frequency-dispersive and non-dispersive equations is highlighted.

During the earthquake that occurred on February 6, 2012, between the Negros and Cebu islands (Philippines), a scuba diver who was about 12 km from the epicenter zone, in about 10 m water depth, was taking audio and video recordings using a GoPro camera. The recorded audio reveals a specific spectral signature few seconds after the earthquake occurrence that appears to be related to hydroacoustic waves. Numerical reproduction of the phenomenon produced waves exhibit a frequency spectrum similar to that recorded. Several previous researches, based on theoretical and/or numerical approaches, indicate that hydroacoustic waves are tsunami precursors and can significantly improve the Tsunami Early Warning System. Currently, such pressure waves generated by submarine earthquakes are seldom measured. Therefore, the records presented in this paper can enhance the research on the in situ data analysis.

This paper describes new physical model tests aiming at measuring both wave overtopping and wave induced forces on rubble mound breakwater crown walls. The physical model and the equipment used for the measurements are described in detail. For the completed tests, a detailed analysis is reported, by evaluating the properties of the incoming waves at the toe of the breakwater and some statistical parameters to describe the wave induced forces and pressures on the crown wall. Careful analysis is also carried out to evaluate how the distribution of the pressures changes with time. It is found that the upper part of the wall is subjected to the first large quasi-impulsive action of the wave; the lower part of the wall is afterwards flooded and a quasi-hydrostatic pressure develops along the height of the wave wall. As far as the pressures on the base of the crown wall are concerned, they develop after a quite large time lag after the maximum of the horizontal force. First attempts to correlate the maximum horizontal force with some explanatory variables such as the ratio of the crest freeboard and of the significant wave height of the incoming waves indicate a promising correlation, also in agreement with the existing literature on the topic. The overtopping rate are also measured and compared with empirical formulas. The correlation between the wave induced forces and the average overtopping discharge on the breakwater is also investigated.

We present a depth integrated numerical model for the simulation of the generation and the propagation of tsunamis generated by submerged landslides. The model is able to reproduce at low computational costs the full frequency dispersion of the waves and uses an ad hoc treatment for the incorporation of the effects of the moving seafloor to reproduce the generation of the waves. We also compare the present approach with some simplified techniques used in the past for the generation of these waves in depth integrated models, and we highlight the different behavior of frequency-dispersive and non-dispersive model equations. Reference solutions for comparison and discussion are obtained from the application of a three dimensional solver of the Laplace equation. All the numerical models used in this research are based on linearized model equations and boundary conditions and are therefore expected to provide reliable results for problems involving small amplitude waves and small thickness landslides. The model seems to be useful for rapid and accurate estimation of the properties of landslide generated waves, and can be used to support a tsunami early warning system. (C) 2009 Elsevier Ltd. All rights reserved.

A numerical model based on the mild-slope equation is applied to reproduce the propagation of small-amplitude transient waves. The model makes use of the Fourier Transform to convert the time-dependent hyperbolic equation into a set of elliptic equations in the frequency domain. The results of two available experimental studies on tsunamis generated by landslides are used to validate the model, which appears to be able of carefully reproducing the effects of the frequency dispersion. An example application of tsunamis propagating around the Stromboli island is also presented to show the applicability of the present approach to real life scenarios. It is finally discussed how this model could be applied as support to a tsunami early warning system. (C) 2008 Elsevier B.V. All rights reserved.

Detection of low-frequency hydro-acoustic waves as precursor components of destructive tsunamis can enhance the promptness and the accuracy of Tsunami Early Warning Systems (TEWS). We reconstruct the hydro-acoustic wave field generated by the 2012 Haida Gwaii tsunamigenic earthquake using a 2-D horizontal numerical model based on the integration over the depth of the compressible fluid wave equation and considering a mild sloped rigid seabed. Spectral analysis of the wave field obtained at different water depths and distances from the source revealed the frequency range of low-frequency elastic oscillations of sea water. The resulting 2-D numerical model gave us the opportunity to study the hydro-acoustic wave propagation in a large-scale domain with available computers and to support the idea of deep-sea observatory and data interpretation. The model provides satisfactory results, compared with in situ measurements, in the reproduction of the long-gravitational waves. Differences between numerical results and field data are probably due to the lack of exact knowledge of sea bottom motion and to the rigid seabed approximation, indicating the need for further study of poro-elastic bottom effects.

Tsunamigenic fast movements of the seabed generate pressure waves in weakly compressible seawater, namely hydro-acoustic waves, which travel at the sound celerity in water (about 1500 m s−1). These waves travel much faster than the counterpart long free-surface gravity waves and contain significant information on the source. Measurement of hydro-acoustic waves can therefore anticipate the tsunami arrival and significantly improve the capability of tsunami early warning systems. In this paper a novel numerical model for reproduction of hydro-acoustic waves is applied to analyze the generation and propagation in real bathymetry of these pressure perturbations for two historical catastrophic earthquake scenarios in Mediterranean Sea. The model is based on the solution of a depth-integrated equation, and therefore results are computationally efficient in reconstructing the hydro-acoustic waves propagation scenarios.

The paper presents a numerical model to reproduce the tsunami generation and propagation, which can be applied in real-time to be used as a forecasting tool. Free surface elevation measurements in a point close to the tsunami generation area, allows the real-time prediction of tsunami in the far field. This is possible due to an inversion technique. The measurements and modeling of hydro-acoustic waves could shorten the time for spreading the alarm and reduce the number of false alerts. In the paper new investigation about hydro-acoustic waves are also presented in order to outline their possible use to support Tsunami Early Warning System.

We present a depth-integrated equation for the mechanics of propagation of low-frequency hydroacoustic waves due to a sudden bottom displacement associated with earthquakes. The model equation can be used for numerical prediction in large-scale domains, overcoming the computational difficulties of three-dimensional models and so creating a solid base for tsunami early warning systems.

Tsunami are long water waves generated by sudden disturbances of the sea floor or sea water surface, which is usually caused by earthquakes, landslides or volcanic eruptions. Once triggered the tsunami can propagate over long distances, carrying destruction even on far coasts, hours after the impulsive generating event. The tragic consequences of the tsunami occurred the 26th December 2004 in the Indian Ocean, involved the scientific community to develop models able to reproduce the tsunami generation and their evolution, with the aim of building Tsunami Early Warning Systems. A single model is not able to treat adequately the generation, propagation and inundation phase of tsunami scenarios, because it can not be at the same time accurate and computational efficient. The tsunami generation most of the times requires the solution of the full three dimensional equations of the hydrodynamics (Grilli et al., 2002; Liu et al., 2005), in order to accurately reproduce the complex sea floor motion and therefore the consequent wave field. A mathematical problem which solves the three dimensional equations is especially needed when tsunami are generated by landslides or small submarine earthquakes. An other important feature which has to be taken into account when modelling the tsunami generation, are the nonlinear terms, which allow the reproduction of waves with a wave height of the same order of the water depth. The nonlinear equations have to be solved when the generating seismic event occurs close to the coast in shallow water, which represents the most dangerous threat for people and structures. When the tsunami propagates far from the generating source it can reach high celerity, of the order of thousands of m/s. Tsunamis in deep water are long waves (wave length of the order of hundreds kilometres) with wave height of the order of one meter; therefore, if compared to the water depth (thousands of metres), can be considered small amplitude water waves. The tsunami propagation phase can therefore be accurately modelled using linear equations. When the wave propagation is to be studied over large geographical areas it appears natural to apply simplified equations in order to reduce the computational costs. These are the depth-integrated equations which reduce the full three-dimensional problem to a two-dimensional one, making the resulting model applicable over oceanic length scales. The most widely equations used are the long wave equations, named also Nonlinear Shallow Water Equations (NSWE). One weak point of the NSWE is that they are not able to reproduce properly the celerity at which each component of the wave field propagates.

Pressure waves generated by fast seabed movement in weakly compressible sea water, namely hydro-acoustic waves travel at the sound celerity in water (about 1500 m/s). These waves are precursors of the counterpart long free-surface gravity waves and contain significant information on the tsunamigenic source. Measurement of hydro-acoustic waves can therefore anticipate the tsunami arrival and significantly enhance the promptness and accuracy of tsunami early warning systems. In this paper derivation of a novel depth-integrated numerical model for reproduction of hydroacoustic waves is presented and the application of this computationally ecient model on two devastating historical tsunamis of Mediterranean Sea in real bathymetry analyzed to reveal the eect of variable bathymetry. On the basis of the model results, some hints for deep sea observatory are given.