Marcello Di Risio

Forecasting Landslide Generated Tsunamis: a Review

When earthquakes occur, suddenly bottom deformations will induce water response that is almost instantaneous. Then, bottom displacements affect wide areas and generate transient waves (tsunamis) usually characterized by a relatively small heightwith respect to their length, i.e. by a small steepness. Indeed, just after the earthquake, the water free surface mimics the final bottom deformations, that can be of the order of some meters, and small amplitude long waves start to propagate resulting in a potential transoceanic devastation (Synolakis et al., 2002). When either subaerial or submerged landslides occur, thedisplacementswill takeplace onboth larger temporal-, and smaller spatial-scale. The deformations are of the order of hundreds of meters and the generated waves are quite different from those induced by submarine earthquakes. Hence, landslide tsunamis tend to be a local phenomenon, although extreme. Since two centuries ago, submarine failures were related to “sea waves without earthquake” when great waves were observed without any account of earthquakes (e.g. Mallet & Mallet, 1858; Milne, 1898; Montessus de Ballore, 1907). In an illuminating reasoning Mallet & Mallet (1858) argued that “great underwater slippage takes place [...] the effect upon the surface of the sea is at the same moment to originate a positive and a negative wave. [...] The magnitude of the wave raised is dependent upon that of the mass of solid material that has suddenly changed its place, upon the depth of water in which the slippage has occurred, upon the rapidity of the transposition, and in minor degree upon the form and material of the portion of the bank that has slipped.” One of the more meaningful event occurred at Lituya Bay (Alaska, July 9, 1958), when a subaerial landslide triggered by an earthquake entered the water at the Gilbert Inlet and generated an impulse wave (Miller, 1960). The induced run-up was the highest known: the water rose up to 524m at the slope in front of the landslide, then thewaves propagated into the Bay and eventually radiated offshore through the Bay inlet with minimum effects outside the Bay itself. Another example, related to submarine failures, is the well documented tsunami generated by an underwater slump triggered by a magnitude 7 earthquake on July 17, 1998 close to the Sissano Lagoon, Sandaun Province, Papua NewGuinea (see Synolakis et al., 2002). The tsunami struck about 30 km wide area, i.e. rather small, by inducing a maximum run-up of about 15 m and killing over 2100 people. Landslide generated impulse waves can occur not only at the sea boundaries, but also in enclosed basins (i.e. reservoirs and lakes). The event that took place at the Vajont Valley (Italy) on October 9, 1963 is perhaps the more sorrowful one. A subaerial landslide of about 6

Algorithms for Automatic, Real-Time Tsunami Detection in Sea Level Measurements

Automatic, real-time tsunami detection in sea-level measurements is a main component of a tsunami early warning system (TEWS). Although a great effort has been recently undertaken by the scientific and engineering community in developing new technologies (e.g. satellite altimetry, detectors of low-frequency elastic oscillations associated to a tsunami) capable of increasing the awareness of potential tsunamis in the minimum amount of time, at present direct detection in sea level measurements is still the main mean to confirm their actual generation and propagation. Clearly, the device used to collect these measurements has to be chosen between those equippedwith sensors capable of detecting sea-level oscillationswithin the tsunami frequency band. At present, the main devices that can be actually used should belong to the following classes:

Engineering Tools for the Estimation of Dredging-Induced Sediment Resuspension and Coastal Environmental Management

In recent years, increasing attention has been paid to environmental impacts that may re‐ sult from resuspension, sedimentation and increase in concentration of chemicals during dredging activities. Dredging dislodges and resuspends bottom sediments that are not captured by dredge-head movements. Resuspended sediments are advected far from the dredging site as a dredging plume and the increase in the suspended solid concentration (SSC) can strongly differ, in time and space, depending on site and operational condi‐ tions. Well-established international guidelines often include numerical modelling appli‐ cations to support environmental studies related to dredging activities. Despite the attention that has been focused on this issue, there is a lack of verified predictive techni‐ ques of plume dynamics at progressive distances from the different dredging sources, as a function of the employed dredging techniques and work programs, i.e., spatial and temporal variation of resuspension source. This chapter illustrates predictive techniques to estimate the SSC arising from dredges with different mechanisms of sediment release and to assess the spatial and temporal variability of the resulting plume in estuarine and coastal areas. Predictive tools are aimed to support technical choices during planning and operational phases and to better plan the location and frequency of environmental moni‐ toring activities during dredging execution.

Post-Event Site Investigation, Monitoring, Stability Analysis, and Modeling of a Gas Pipeline Explosion

This paper describes the results of site investigations, monitoring, stability analyses, and soil-pipe interaction modeling of a built-up slope located near Pineto (Abruzzo Province, Central Italy), where a gas pipeline exploded on March 6th, 2015, due to heavy rains inducing slope movements. The slope is formed by OC clay, covered with an upper 10- to 14-m-thick clayey-sandy silt colluvial layer. The explosion in the upper portion of the slope caused extensive damage to existing buildings and threatened human lives. Soon after the event, a site investigation and monitoring program was carried out. A detailed topographic survey and hydrological data were analyzed in order to characterize possible critical rainfall events. The stability of the slope was analyzed both in pre- and in post-explosion conditions. The profiles of the DMT horizontal stress index KD helped to identify multiple slip surfaces. Then, the results of the site investigation and stability analyses were used to implement a simplified finite element model aimed to describe the soil-pipeline interaction, taking into account the role of the observed wrinkle in the pipeline. The numerical simulations reveal the crucial role played by the slope movements, and by the wrinkle as well, in inducing the collapse of the pipe.

Met-ocean and heeling analysis during the violent 21/22 october 2014 storm faced by the sailboat ECO40 in the gulf of lion: Comparison between measured and numerical wind data

On 19 October 2014 Matteo Miceli, a known italian oceanic sailor, left the Port of Riva di Traiano (Rome, IT) with the italian sailing boat ECO 40, for the Roma Ocean World Project. This ambitious challenge consists of a non-stop sailing alone around the World in energy and food self-sufficiency. ECO 40 is a Class 40 oceanic vessel (LOA of 12,0 m) that has been equipped with a data acquisition system for measuring both the met-ocean parameters recorded (apparent and real wind speed and wind direction, atmospheric pressure, current velocity, air temperature, sea temperature, etc.) and the kinematic characteristics of the boat itself (i.e., speed and course over ground). Furthermore, the boat has been equipped with three high precision GPS receivers, provided by Leica Geosystem, for measuring the motion of the boat and an inertial platform. Due to these high-precision instruments it is possible to fully measure and characterize the six degrees of freedom of the boat, and accordingly to use her as a sailing wave buoy. Within this paper we present the analysis of the met-ocean data measured by the boat during the storm occurred in the Gulf of Lion on the 21–22 October 2014 that ECO 40 has faced just few days after her departure. Furthermore, by analyzing the GPS signals by means of an innovative application of differential kinematic positioning technique, a detailed analysis of the boat heeling during the Gulf of Lion event has been carried out. The boat heeling measurements have been used to correct the measured wind data that have been compared with the hindcast time series.