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This paper presents new tests on a perforated vertical wall caisson. The tests aim at evaluating the reduction of the reflection coefficient caused by different perforations. The reflection coefficient is estimated using the novel nonlinear methods proposed by Lykke Andersen et al. (2017) and Eldrup and Lykke Andersen (2019). The structure under investigation is, at prototype scale, 21.50 m high, 35.55 m long and 13.90 m wide, divided into 3 rows of 8 cells. The caisson has a recurved ‘nose’ and air vents on the parapet wall. An identical plain wall caisson without absorbing chambers is also tested for comparison. Two-dimensional laboratory tests have been carried out at Department of Engineering of Roma Tre University with both irregular and regular waves, reproducing mild wave conditions and design wave conditions. Two water levels have been used, reproducing the mean water level and a set-up condition of +0.5 m. Four structural layouts are tested in order to study various perforation types. Furthermore, the effect of the wave obliquity and of the short crestedness on the reflection coefficient is discussed using some 3D laboratory data obtained back in the 1995 but not published before.

This paper presents a numerical model based on the mild-slope equation (MSE for short) suitable to reproduce the propagation of small amplitude tsunamis in the off-shore field. The model solves the governing equations in the frequency domain and allows the reproduction of the frequency dispersion for broad banded spectrum sea states. The model application to reproduce laboratory experiments and real life tsunamis in the south Tyrrhenian sea (Mediterranean Sea) are described, showing its applicability to relative large geographical areas. The proposed method is suitable to support a real time tsunami early warning system.

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.

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.

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.

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.

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.

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.

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.