Three‐dimensional tsunami propagation simulations using an unstructured mesh finite element model

Oishi, Y.; Piggott, Matthew D.; Maeda, Takuto; Kramer, Stephan C.; Collins, G. S.; Tsushima, Hiroaki; Furumura, Takashi

doi:10.1002/jgrb.50225

Cited by 24 publications

(27 citation statements)

References 39 publications

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“…The NDS simulation also needs to employ an implicit scheme to stably calculate the dispersion while the NLL employs an explicit scheme. If you consider a practical application for tsunami early warning, developing a more efficient method to solve the NDS equations on supercomputers is necessary [e.g., Lynett et al, 2002;Saito and Furumura, 2009;Kirby et al, 2012;Shi et al, 2012;Oishi et al, 2013]. For this purpose, it is a good compromise to use the DSP equations for source estimation and propagation across the ocean, and to use the NLL equations for tsunami and inundation predictions near the coast.…”

Section: Discussion On Tsunami Waveform Modelingmentioning

confidence: 99%

Dispersion and nonlinear effects in the 2011 Tohoku‐Oki earthquake tsunami

et al. 2014

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This study reveals the roles of the wave dispersion and nonlinear effects for the 2011 TohokuOki earthquake tsunami. We conducted tsunami simulations based on the nonlinear dispersive equations with a high-resolution source model. The simulations successfully reproduced the waveforms recorded in the offshore, deep sea, and focal areas. The calculated inundation area coincided well with the actual inundation for the Sendai Plain, which was the widest inundation area during this event. By conducting sets of simulations with different tsunami equations, we obtained the followings insights into the wave dispersion, nonlinear effects, and energy dissipation for this event. Although the wave dispersion was neglected in most studies, the maximum amplitude was significantly overestimated in the deep sea if the dispersion was not included. The waveform observed at the station with the largest tsunami height ($2 m) among the deep-ocean stations also verified the necessity of the dispersion. It is well known that the nonlinear effects play an important role for the propagation of a tsunami into bays and harbors. Additionally, nonlinear effects need to be considered to accurately model later waves, even for offshore stations. In particular, including nonlinear terms rather than the inundation was more important when precisely modeling the waves reflected from the coast.

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Section: Discussion On Tsunami Waveform Modelingmentioning

confidence: 99%

Dispersion and nonlinear effects in the 2011 Tohoku‐Oki earthquake tsunami

et al. 2014

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“…The reason for choosing an isotropic viscosity is that experiments showed no discernible differences in results when using different values of viscosity in the horizontal and vertical when using a single layer of elements. This may not be the case when multiple layers are used to capture dispersion (Oishi et al, 2013). X is the rotational velocity of the Earth and g is the gravitational acceleration with k pointing in the radial, upward direction.…”

Section: Fluiditymentioning

confidence: 99%

“…Wells et al, 2010;Hill et al, 2012;Hiester et al, 2011). In an ocean modelling context, Fluidity has been used to model both modern and ancient earthquake-generated tsunamis (Oishi et al, 2013;Mitchell et al, 2010;Shaw et al, 2008). Here, Fluidity is used to solve the non-hydrostatic incompressible Navier-Stokes equations under the Boussinesq approximation in a rotating reference frame: @u @t…”

Section: Fluiditymentioning

confidence: 99%

“…A combined pressure-free-surface kinematic boundary condition formulation is employed as the top boundary condition (Funke et al, 2011;Oishi et al, 2013). A no-normal flow with a quadratic bottom drag, with dimensionless coefficient C D set to 0.0025, is applied at the bottom, except where the slide motion is prescribed (see Section 2.2).…”

Section: Fluiditymentioning

confidence: 99%

“…Fluidity has previously been used to simulate earthquake-generated tsunami (Shaw et al, 2008;Mitchell et al, 2010;Oishi et al, 2013). Oishi et al (2013) showed that Fluidity could accurately simulate the 2011 Japanese tsunami and, in particular, was able to represent the dispersive effects of the tsunami by using multiple vertical layers. We do not consider the effects of dispersion here due to the size of the Storegga slide.…”

Section: Introductionmentioning

confidence: 99%

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How does multiscale modelling and inclusion of realistic palaeobathymetry affect numerical simulation of the Storegga Slide tsunami?

et al. 2014

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a b s t r a c tThe $8.15 ka Storegga submarine slide was a large ($3000 km 3 ), tsunamigenic slide off the coast of Norway. The resulting tsunami had run-up heights of around 10-20 m on the Norwegian coast, over 12 m in Shetland, 3-6 m on the Scottish mainland coast and reached as far as Greenland. Accurate numerical simulations of Storegga require high spatial resolution near the coasts, particularly near tsunami run-up observations, and also in the slide region. However, as the computational domain must span the whole of the Norwegian-Greenland sea, employing uniformly high spatial resolution is computationally prohibitive. To overcome this problem, we present a multiscale numerical model of the Storegga slide-generated tsunami where spatial resolution varies from 500 m to 50 km across the entire NorwegianGreenland sea domain to optimally resolve the slide region, important coastlines and bathymetric changes. We compare results from our multiscale model to previous results using constant-resolution models and show that accounting for changes in bathymetry since 8.15 ka, neglected in previous numerical studies of the Storegga slide-tsunami, improves the agreement between the model and inferred runup heights in specific locations, especially in the Shetlands, where maximum run-up height increased from 8 m (modern bathymetry) to 13 m (palaeobathymetry). By tracking the Storegga tsunami as far south as the southern North sea, we also found that wave heights were high enough to inundate Doggerland, an island in the southern North Sea prior to sea level rise over the last 8 ka.

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Traveltime delay and initial phase reversal of distant tsunamis coupled with the self‐gravitating elastic Earth

2014

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Systematic tsunami traveltime delays of up to 15 min relative to the numerically simulated long waves from the 2010 Chilean and 2011 Tohoku-Oki earthquakes were widely observed at deep ocean tsunamimeters. Enigmatic small negative phases appearing before the main peak were commonly found only at the trans-oceanic locations. The frequency dependence of the measured tsunami phase velocities shows reverse dispersions at long periods, i.e., the tsunami speed becomes slower at periods beyond 1000 s. This is consistent with the phase velocities of a tsunami mode coupled with a self-gravitating elastic Earth, suggesting that the effects of compression and dilatation of seawater, elastic tsunami loadings on a solid Earth, and the geopotential variations associated with the motion of mass during tsunami propagation are responsible for the traveltime delays and the initial negative phases. Simple 1-D tsunami propagation tests confirm that the reverse dispersion creates a small negative phase that precedes the main peak at large distances. A new method to simulate tsunami waveforms on real ocean bathymetry that takes into account seawater compressibility, the elasticity of the Earth, and geopotential perturbations has been developed by applying a phase correction to the simulated long waves. The simulated waveforms, in which phase corrections are applied for the dispersion effects, accurately reproduce the observed waveforms, including a small initial negative phase that appears at distant locations. The traveltime difference between the observed and simulated waveforms has been decreased to less than 5 min and the waveform difference between them remarkably diminishes.

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Three‐dimensional tsunami propagation simulations using an unstructured mesh finite element model

Cited by 24 publications

References 39 publications

Dispersion and nonlinear effects in the 2011 Tohoku‐Oki earthquake tsunami

Dispersion and nonlinear effects in the 2011 Tohoku‐Oki earthquake tsunami

How does multiscale modelling and inclusion of realistic palaeobathymetry affect numerical simulation of the Storegga Slide tsunami?

Traveltime delay and initial phase reversal of distant tsunamis coupled with the self‐gravitating elastic Earth

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