Numerical modelling of tsunami generation and propagation from submarine slumps: the 1998 Papua New Guinea event

Abstract

SUMMAR YDeep and large submarine slumps may generate tsunamis as disastrous as tsunamis of tectonic origin. Such a landslide is likely to be the origin of the 1998 July 17 tsunami of Papua New Guinea, the deadliest tsunami in the last 50 years. Water waves devastated a 20 km stretch of coastline, wiping out three villages and killing more than 2200 people. A numerical model has been developed to study the efficiency of deep slumps in producing tsunamis and has been applied to the Papua New Guinea event.The landslide is treated as the flow of a homogeneous gravity-driven continuum governed by a rheological law. Water waves are generated by sea-bottom displacements induced by the landslide. The shallow-water approximation is adopted for both the landslide and the associated water waves. The resulting differential equations are solved by a finite difference method based on shock-capturing. The shallow-water hypothesis is tested by comparison with a model solving Navier-Stokes equations for a mixture of water and sediments. Sensitivity tests carried out for a 2-D simplified geometry show that the water surface profile depends strongly on the constitutive law of the landslide.The 1998 event is simulated numerically by the shallow-water model, testing different friction laws. The observed inundation height distribution is well reproduced by the model for a volume of 4 km 3 , with its top located at a water depth of 550 m, and sliding with a Coulomb-type friction law over a distance of 5 km.

Owen Ridge deep-water submarine landslides: implications for tsunami hazard along the Oman coast

“…Since the slide thickness (140 m at the initiation) is much smaller than the slide length in the case study, the Bingham model can be simplified by considering a single layer whose motion is initiated and driven by viscosity when the shear stress exceeds a given yield stress (Norem et al, 1991;McEwen and Malin, 1989). The resulting equations of mass and momentum conservation, written in a coordinate system linked to the topography, read (see Heinrich et al, 2001) where κ =1−ρ w /ρ s , τ xz (z=0) and τ xy (z=0) are the shear stresses at the bed surface, u = (u,v) is the depth-averaged velocity vector parallel to the bed, h is the slide thickness perpendicular to the slope, ρ w and ρ s are the water and sediments densities with a ratio ρ w /ρ s =2, θ(x,y) is the local steepest slope angle, θ x and θ y are the slope angles along xand y-axes, respectively. Values of α that deviate from unity provide information about the deviation of the slope normal profile of (u, v) from uniformity.…”

“…Equations governing the landslide and the tsunami propagation are similar and non-dispersive. They are thus solved using the same Godunov-type scheme, extended to second order by using the concept of Vanleer (Alcrudo and Garcia-Navarro, 1993; Mangeney et al, 2000), which is based on a shock-capturing method originally derived from gas dynamics models (Heinrich et al, 2001). This model is particularly adapted to deal with nonlinear waves.…”

“…We use the AVALANCHE code that has been described in details and successfully tested for the 1998 Papua New Guinea event (Heinrich et al, 2001) and the 1979 Nice event (Labbé et al, 2012). The model is based on the shallow water assumption, with slide thickness much smaller than its length and width.…”

The 1998 Papua New Guinea Earthquake and its Fault Plane Estimated from Relocated Aftershocks

“…MATSUYAMA et al (1999), in a numerical simulation employing the newly obtained bathymetric data, concluded that only a low-angle reverse fault model accompanied by a large underwater landslide could explain the 1998 PNG tsunami. HEINRICH et al (2000HEINRICH et al ( , 2001 showed that a submarine landslide could closely simulate the PNG tsunami. GEIST (2000GEIST ( , 2001, OKAL and SYNOLAKIS (2001) have discussed whether earthquakes or landslides cause tsunami.…”

Application of Analytical Modeling to the Far-field Investigation of Tsunami and Oceanic Rayleigh Waves from the 1998 Papua New Guinea Earthquake

“…HEINRICH et al (2001) have carried out a finitedifference landslide and tsunami simulation in the near-field zone based on a shallowwater approximation. In their model, water waves were generated by sea-bottom displacements induced by a landslide.…”