Abstract
Abstract. The 1958 Lituya Bay landslide-generated mega-tsunami is simulated using the Landslide-HySEA model, a recently developed finite-volume Savage–Hutter shallow water coupled numerical model. Two factors are crucial if the main objective of the numerical simulation is to reproduce the maximal run-up with an accurate simulation of the inundated area and a precise recreation of the known trimline of the 1958 mega-tsunami of Lituya Bay: first, the accurate reconstruction of the initial slide and then the choice of a suitable coupled landslide–fluid model able to reproduce how the energy released by the landslide is transmitted to the water and then propagated. Given the numerical model, the choice of parameters appears to be a point of major importance, which leads us to perform a sensitivity analysis. Based on public domain topo-bathymetric data, and on information extracted from the work of Miller (1960), an approximation of Gilbert Inlet topo-bathymetry was set up and used for the numerical simulation of the mega-event. Once optimal model parameters were set, comparisons with observational data were performed in order to validate the numerical results. In the present work, we demonstrate that a shallow water type of model is able to accurately reproduce such an extreme event as the Lituya Bay mega-tsunami. The resulting numerical simulation is one of the first successful attempts (if not the first) at numerically reproducing, in detail, the main features of this event in a realistic 3-D basin geometry, where no smoothing or other stabilizing factors in the bathymetric data are applied.
Highlights
Tsunamis are most often generated by bottom displacements due to earthquakes
At 06:16 UTC on 10 July 1958, a magnitude Mw 8.3 earthquake occurred along the Fairweather Fault (Alaska, USA). This quake triggered a landslide of approximately 30.6 Mm3 in Gilbert Inlet (Miller, 1960) that in turn produced the largest tsunami run-up ever recorded (Fritz et al, 2009)
The EDANYA group has implemented a finite-volume numerical model, the Landslide-HySEA model (Castro et al, 2005, 2006, 2008, 2012; Gallardo et al, 2007; Macías et al, 2012, 2015; de la Asunción et al, 2013), for the simulation of submarine landslides based on the two-layer Savage–Hutter model introduced in Fernández-Nieto et al (2008) that takes into account the movement of the fluid inside which the avalanche develops
Summary
Tsunamis are most often generated by bottom displacements due to earthquakes. landslides, either submarine or subaerial, can trigger devastating tsunami waves. The case of subaerial-landslide-generated tsunamis is where modeling and numerical implementation becomes most critical, owing to these events producing more complex flow configurations, larger vertical velocities and accelerations, cavitation phenomena, dissipation, dispersion, and complex coupled interaction between landslide and water flow. In the case of tsunamigenic aerial landslides in fjords, bays, or any long and narrow water body, confinement and reflection (a process that makes propagation and interaction more complex) are relatively more important considerations than dispersion, which becomes less important This is true for the leading wave (Løvholt et al, 2015) that, is mainly responsible for coastal impact. As far as we know, the present work represents the first successful attempt to realistically simulate and reproduce the 1958 Lituya Bay mega-tsunami in a realistic three-dimensional geometry with no smoothing in the geometry or initial conditions
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