Wave and run-up (tsunami) reconstruction from ancient submarine-landslide in the Gulf of Naples, Italy (Abstract/Poster in atti di convegno)

  • Wave and run-up (tsunami) reconstruction from ancient submarine-landslide in the Gulf of Naples, Italy (Abstract/Poster in atti di convegno) (literal)
  • 2008-01-01T00:00:00+01:00 (literal)
Alternative label
  • Vincenzo Di Fiore; Gemma Aiello; Antimo Angelino (2008)
    Wave and run-up (tsunami) reconstruction from ancient submarine-landslide in the Gulf of Naples, Italy
    in Convegno Nazionale GNGTS 2008, Roma
  • Vincenzo Di Fiore; Gemma Aiello; Antimo Angelino (literal)
  • Articolo in Atti di Convegno Nazionale (literal)
  • Nessuna (literal)
  • Abstract e poster a convegno nazionale (literal)
  • ISI Web of Science (WOS) (literal)
  • Abstract (literal)
  • CNR-IAMC Sede di Napoli (literal)
  • Wave and run-up (tsunami) reconstruction from ancient submarine-landslide in the Gulf of Naples, Italy (literal)
  • The aim of this paper is the study of the wave and run-up generation caused by ancient submarine landslides located in the canyon of the Naples Bay. Theoretical models for describing the generation and propagation of the water waves induced by submarine landslides have been recently proposed by Lynett and Liu (2002). The continental slope off the Naples Bay represents an excellent natural laboratory to study geological events and processes related to the development of submarine slides and their tsunamigenic potential. The geological setting of the Naples Bay has been studied in detail in the frame of research programmes of marine geological cartography of the Naples Bay (Aiello et al., 2001; Bruno et al., 2003; D'Argenio et al., 2004; Aiello et al., 2004; 2005; Ruggieri et al., 2007). Landslide generated tsunamis in the Ischia island has been recently evaluated by Zaniboni et al. (2007) in the frame of the INGV-DPC project V3 on volcanic hazard and risk assessment associated to the Ischia volcanic complex, north-west of the Gulf. The authors focussed, on the study of tsunamis generated by possible landslides from Ischia slopes. The catastrophic collapse that formed the large scar in the southern flank of the Ischia island (The Ischia Debris Avalanche; Chiocci and de Alteriis, 2006) can be considered as the upper limit for tsunamigenic failures in the Ischia island, but the repetition of such an event is very improbable. A new catalogue of Italian tsunamis (ITC) has been recently purposed by the INGV (Tinti et al., 2001; 2003) in the frame of the studies of European and Italian tsunamis. The ITC contains 67 events, covering the period from the tsunamigenic Plinian eruption of Vesuvius (79 A.C.) until today. The Gulf of Naples continental slope and outer shelf are deeply incised by two submarine canyons of kilometric extension, namely the Dohrn and Magnaghi canyons, representing the drainage system of this active volcanic area during the Late Quaternary. Detailed mapping of morphological features in the outer shelf and slope contributed to the knowledge of erosional and depositional processes related to the continental slope settngs and allowed on the geological interpretation of marine DEM of Dohrn and Magnaghi canyons recorded in the frame of CARG Project of marine geological mapping of the Naples Bay (Aiello et al., 2001; D'Argenio et al., 2004; Ruggieri et al., 2007). The north-western branch of the Dohrn canyon is affected by instability, with an incipient slump causing a broad depression, 200-300 m across, away from the canyon edge and semi-circular scours on the canyon walls with lateral coalescence and presentes a large area of instability, located westward of the north-western slope of the Banco di Fuori morpho-structural high. Significant slide scars in this submarine sector have been evidenced also by bathymetric profiles across the slope (Ruggieri et al., 2007). No slumped masses are preserved in the main thalweg, suggesting a probable activity of low-density turbidity currents during the Late Quaternary activity of the canyon. Large isolated blocks, showing average dimensions of 300x400m are present on the canyon floor and in its upper part the canyon floor is scoured by a minor meandering channel. These rounded morphologies are interpreted as relic structures, probably due to a selective erosion acting along the canyon's valley. On the contrary, the Magnaghi canyon is incised in the Late Quaternary volcanic deposits of the Ischia and Procida islands. A bathymetric profile has been constructed in correspondence to the scars involving the Dohrn western branch in order to give quantitative constraints to the numerical modelling. A detachment area, large about 415 m occurs at water depths ranging between - 250 m and - 370 m. Debris accumulation occurs at water depths ranging from - 380 m and - 450 m, where the junction with the foot of the thalweg appears, at water depths of about - 430 m. In this paper, we present a mathematical model described in Lynett et al. (2002), in which the generation and propagation of tsunamis is reconstructed from ancient submarine landslides. In such a model there is the assumption of weak frequency dispersion, i.e. the ratio of water depth or wavelength is small or less than 1. In general, for dispersive properties the depth-integrated equations are valid only for wavelengths greater than two water depths, whereas, the depth-averaged model is valid for lengths greater than five water depths (e.g. Nwogu, 1993). After integral resolution of the two-dimensional governing equation, we applied the finite difference algorithm to resolve the general model equation (Lynett et al., 2002). In their paper Lynett et al. (2002) developed the algorithm for the general two-horizontal dimension problem similar to Wei and Kirby (1995) and Wei et al. (1995). In this study we consider an impulsive bottom movement in a constant water depth. The bottom movement consists of a length l0=620 m, which pushed vertically upward. This change in depth for this experiment is about 0.1 and therefore nonlinear effects should play a small role near the source region. The landslide is located near the Dohrn Canyon head and we hypothesize that the landslide is quickly occurred too. To analyze the model we Introduce the characteristic water depth h0 as the vertical length scale, the characteristic length of the submarine slide region l0 as the horizontal length-scale and the characteristic wave amplitude a0 as the scale of wave motion. The amplitude wave run-up expressed in terms of depth seafloor percentages, ranges from 0 to 2,5 %. In absolute terms the wave height amplitude corresponds to 5-6 m. (literal)
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