scholarly journals TSUNAMI PHASE SPEED REDUCTION DUE TO WATER COMPRESSIBILTY

2018 ◽  
pp. 9
Author(s):  
Ali Abdolali ◽  
James T. Kirby
Keyword(s):  
Arrival Time ◽  
Phase Speed ◽  
Propagation Speed ◽  
Frequency Dispersion ◽  
Wave Theory ◽  
Polar Coordinates ◽  
Ocean Bottom ◽  
Tsunami Propagation ◽  
Boussinesq Model ◽  
Tsunami Waves

Most existing tsunami propagation models consider the ocean to be an incompressible, homogenous medium. Recently, it has been shown that a number of physical features can slow the propagation speed of tsunami waves, including wave frequency dispersion, ocean bottom elasticity, water compressibility and thermal or salinity stratification. These physical effects are secondary to the leading order, shallow water or long wave behavior, but still play a quantifiable role in tsunami arrival time, especially at far distant locations. In this work, we have performed analytical and numerical investigations and have shown that consideration of those effects can actually improve the prediction of arrival time at distant stations, compared to incompressible forms of wave equations. We derive a modified Mild Slope Equation for Weakly Compressible fluid following the method proposed by Sammarco et al. (2013) and Abdolali et al. (2015) using linearized wave theory, and then describe comparable extensions to the Boussinesq model of Kirby et al. (2013). Both models account for water compressibility and compression of static water column to simulate tsunami waves. The mild slope model is formulated in plane Cartesian coordinates and is thus limited to medium propagation distances, while the Boussinesq model is formulated in spherical polar coordinates and is suitable for ocean scale simulations.

Seismically Derived Ground Tilts Related to the 2010 Chilean Tsunami

2021 ◽  
Author(s):  
Jui-Chun Freya Chen ◽  
Wu-Cheng Chi ◽  
Chu-Fang Yang
Keyword(s):  
Deep Ocean ◽  
Propagation Model ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Tsunami Propagation ◽  
Ground Tilt ◽  
Tsunami Waves ◽  
The Pacific ◽  
Seismic Networks ◽  
Back Azimuth

Abstract Developing new ways to observe tsunami contributes to tsunami research. Tidal and deep-ocean gauges are typically used for coastal and offshore observations. Recently, tsunami-induced ground tilts offer a new possibility. The ground tilt signal accompanied by 2010 Mw 8.8 Chilean earthquake were observed at a tiltmeter network in Japan. However, tiltmeter stations are usually not as widely installed as broadband seismometers in other countries. Here, we studied broadband seismic records from Japan’s F-net and found ground tilt signals consistent with previously published tiltmeter dataset for this particular tsunamic event. Similar waveforms can also be found in broadband seismic networks in other countries, such as Taiwan, as well as an ocean-bottom seismometer. We documented a consistent time sequence of evolving back-azimuth directions of the tsunami waves at different stages of tsunami propagation through beamforming-frequency–wavenumber analysis and particle-motion analysis; the outcomes are consistent with the tsunami propagation model provided by the Pacific Tsunami Warning Center. These results shown that dense broadband seismic networks can provide a useful complementary dataset, in addition to tiltmeter arrays and other networks, to study or even monitor tsunami propagation using arrayed methods.

Characteristics of Leading Tsunami Waves Generated in Three Recent Tsunami Events

2014 ◽  
Vol 08 (03) ◽  
pp. 1440001 ◽  
Author(s):  
Chao An ◽  
Philip L.-F. Liu
Keyword(s):  
Water Depth ◽  
Wave Amplitude ◽  
Propagation Speed ◽  
Frequency Dispersion ◽  
Wave Period ◽  
Wave Crest ◽  
Haida Gwaii ◽  
Tsunami Waves ◽  
Wave Nonlinearity ◽  
Chile Tsunami

In this paper, the time series of ocean water surface elevation, recorded by Deep-ocean Assessment and Recording of Tsunamis (DART) sensors in the Pacific Ocean, during three recent tsunami events — 2010 Chile tsunami, 2011 Tohoku tsunami, and 2012 Haida Gwaii tsunami — are analyzed. The characteristics of leading tsunami waves are examined in terms of their propagation speed, wave period and wave amplitude so as to determine the importance of wave nonlinearity and frequency dispersion. Using the estimated arrival time of leading waves at each DART station and the distance from each station to the epicenter of the corresponding earthquake, the averaged propagation speed of leading waves for each event is calculated. It is found that the wave propagation speed for 2010 Chile tsunami is roughly 190 m/s, and is slightly slower than that of 2011 Tohoku and 2012 Haida Gwaii tsunamis, 210 m/s for both events. Two time scales associated with the leading waves are introduced: the duration of leading wave crest and the leading wave period obtained from a wavelet analysis. The results show that the leading wave crest duration is roughly 15–20 min and the wave period is roughly 25–30 min at most of DART stations for all the three events. The wave nonlinearity and frequency dispersion parameters, being defined as the wave amplitude to water depth ratio and the square of water depth to wavelength ratio, respectively, are calculated for the leading waves. The parameter for wave nonlinearity is found to be smaller than 4.0 × 10-4, while the parameter for frequency dispersion is smaller than 0.02 at all stations for all the three events. Finally, the cumulative effects of nonlinearity and frequency dispersion for the leading waves are investigated. It is found that the distances between the epicenter and all DART stations in each event are much smaller than those required for the nonlinearity and/or frequency dispersive effects to become significant.

scholarly journals New High-Resolution Modeling of the 2018 Palu Tsunami, Based on Supershear Earthquake Mechanisms and Mapped Coastal Landslides, Supports a Dual Source

2021 ◽  
Vol 8 ◽  
Author(s):  
Lauren Schambach ◽  
Stephan T. Grilli ◽  
David R. Tappin
Keyword(s):  
Partial Information ◽  
Tide Gauge ◽  
Frequency Dispersion ◽  
Tsunami Modeling ◽  
Marine Geology ◽  
Boussinesq Model ◽  
Tsunami Waves ◽  
Dual Source ◽  
Earthquake Models ◽  
Coastal Landslides

The Mw 7.5 earthquake that struck Central Sulawesi, Indonesia, on September 28, 2018, was rapidly followed by coastal landslides and destructive tsunami waves within Palu Bay. Here, we present new tsunami modeling that supports a dual source mechanism from the supershear strike-slip earthquake and coastal landslides. Up until now the tsunami mechanism: earthquake, coastal landslides, or a combination of both, has remained controversial, because published research has been inconclusive; with some studies explaining most observations from the earthquake and others the landslides. Major challenges are the numerous different earthquake source models used in tsunami modeling, and that landslide mechanisms have been hypothetical. Here, we simulate tsunami generation using three published earthquake models, alone and in combination with seven coastal landslides identified in earlier work and confirmed by field and bathymetric evidence which, from video evidence, produced significant waves. To generate and propagate the tsunamis, we use a combination of two wave models, the 3D non-hydrostatic model NHWAVE and the 2D Boussinesq model FUNWAVE-TVD. Both models are nonlinear and address the physics of wave frequency dispersion critical in modeling tsunamis from landslides, which here, in NHWAVE are modeled as granular material. Our combined, earthquake and coastal landslide, simulations recreate all observed tsunami runups, except those in the southeast of Palu Bay where they were most elevated (10.5 m), as well as observations made in video recordings and at the Pantoloan Port tide gauge located within Palu Bay. With regard to the timing of tsunami impact on the coast, results from the dual landslide/earthquake sources, particularly those using the supershear earthquake models are in good agreement with reconstructed time series at most locations. Our new work shows that an additional tsunami mechanism is also necessary to explain the elevated tsunami observations in the southeast of Palu Bay. Using partial information from bathymetric surveys in this area we show that an additional, submarine landslide here, when simulated with the other coastal slides, and the supershear earthquake mechanism better explains the observations. This supports the need for future marine geology work in this area.

scholarly journals Numerical simulation of the tsunamis generated by the Sciara del Fuoco landslides (Stromboli Island, Italy)

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
A. Fornaciai ◽  
M. Favalli ◽  
L. Nannipieri
Keyword(s):  
Wave Propagation ◽  
Tyrrhenian Sea ◽  
Submarine Landslides ◽  
Tsunami Propagation ◽  
Boussinesq Model ◽  
Tsunami Waves ◽  
Aeolian Arc ◽  
Hydrostatic Model ◽  
Southern Tyrrhenian Sea ◽  
Sciara Del Fuoco

AbstractStromboli volcano (Aeolian Arc, Italy) experiences many mass failures along the Sciara del Fuoco (SdF) scar, which frequently trigger tsunamis of various sizes. In this work, we simulate tsunami waves generated by landslides occurring in the SdF through numerical simulations carried out in two steps: (i) the tsunami triggering, wave propagation and the effects on Stromboli are simulated using the 3D non-hydrostatic model NHWAVE; (ii) generated train waves are then input into the 2D Boussinesq model FUNWAVE-TVD to simulate wave propagation in the Southern Tyrrhenian Sea (STS). We simulated the following scenarios: (i) the tsunami runup, inland inundation and wave propagation at Stromboli triggered by submarine landslides with volumes of 6, 10, 15 and 20 × 106 m3 and subaerial landslides with volumes of 4, 6, 10 and 30 × 106 m3; (ii) tsunami propagation in the STS triggered by submarine landslides with volumes of 10 and 15 × 106 m3 and by subaerial landslides with volumes of 6 and 30 × 106 m3. We estimate that the damages of the last relevant tsunami at Stromboli, which occurred in 2002, could have been generated either by a subaqueous failure of about 15–20 × 106 m3 along the SdF or/and a subaerial failure of about 4–6 × 106 m3. The coasts most affected by this phenomenon are not necessarily located near the failure, because the bathymetry and topography can dramatically increase the waves heights locally. Tsunami waves are able to reach the first Stromboli populated beaches in just over 1 minute and the harbour in less than 7 minutes. After about 30 minutes the whole Aeolian Arc would be impacted by maximum tsunami waves. After 1 hour and 20 minutes, waves would encompass the whole STS arriving at Capri.

scholarly journals Eddy Phase Speeds in a Two-Layer Model of Quasigeostrophic Baroclinic Turbulence with Applications to Ocean Observations

2016 ◽  
Vol 46 (6) ◽  
pp. 1963-1985 ◽  
Author(s):  
Lei Wang ◽  
Malte Jansen ◽  
Ryan Abernathey
Keyword(s):  
Practical Importance ◽  
Phase Speed ◽  
Wave Theory ◽  
Inverse Cascade ◽  
Barotropic Mode ◽  
Eddy Fluxes ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Ocean Observations ◽  
Shed Light

AbstractThe phase speed spectrum of ocean mesoscale eddies is fundamental to understanding turbulent baroclinic flows. Since eddy phase propagation has been shown to modulate eddy fluxes, an understanding of eddy phase speeds is also of practical importance for the development of improved eddy parameterizations for coarse resolution ocean models. However, it is not totally clear whether and how linear Rossby wave theory can be used to explain the phase speed spectra in various weakly turbulent flow regimes. Using linear analysis, theoretical constraints are identified that control the eddy phase speed in a two-layer quasigeostrophic (QG) model. These constraints are then verified in a series of nonlinear two-layer QG simulations, spanning a range of parameters with potential relevance to the ocean. In the two-layer QG model, the strength of the inverse cascade exerts an important control on the eddy phase speed. If the inverse cascade is weak, the phase speed spectrum is reasonably well approximated by the phase speed of the linearly most unstable mode. A significant inverse cascade instead leads to barotropization, which in turn leads to mean phase speeds closer to those of barotropic-mode Rossby waves. The two-layer QG results are qualitatively consistent with the observed eddy phase speed spectra in the Antarctic Circumpolar Current and may also shed light on the interpretation of phase speed spectra observed in other regions.

scholarly journals Trapped Planetary (Rossby) Waves Observed in the Indian Ocean by Satellite Borne Altimeters

2017 ◽  
Author(s):  
Yair De-Leon ◽  
Nathan Paldor
Keyword(s):  
Indian Ocean ◽  
Rossby Waves ◽  
Low Frequency ◽  
Propagation Speed ◽  
Wave Theory ◽  
Planetary Waves ◽  
Sea Surface ◽  
Trapped Wave ◽  
The Indian Ocean ◽  
Frequency Variations

Abstract. Using 20 years of accurately calibrated, high resolution, observations of Sea Surface Height Anomalies (SSHA) by satellite ‎borne altimeters we show that in the Indian Ocean south of the Australian coast the low frequency variations of SSHA are ‎dominated by westward propagating, trapped, i.e. non-harmonic, planetary waves. Our results demonstrate that the ‎meridional-dependent amplitudes of the SSHA are large only within a few degrees of latitude next to the South-Australian ‎coast while farther in the ocean they are uniformly small. This meridional variation of the SSHA signal is typical of the ‎amplitude structure in the trapped wave theory. The westward propagation speed of the SSHA signals is analyzed by ‎employing three different methods of estimation. Each one of these methods yields speed estimates that can vary widely ‎between adjacent latitudes but the combination of at least two of the three methods yields much smoother variation. The ‎estimates obtained in this manner show that the observed phase speeds at different latitudes exceed the phase speeds of ‎harmonic Rossby (Planetary) waves by 140 % to 200 %. In contrast, the theory of trapped Rossby (Planetary) waves in a ‎domain bounded by a wall on its equatorward side yields phase speeds that approximate more closely the observed phase ‎speeds.‎

A multi-scenario assessment of the seismogenic tsunami hazard for Bangladesh

2019 ◽  
Vol 11 (2) ◽  
pp. 156-168
Author(s):  
Janaka J. Wijetunge
Keyword(s):  
Subduction Zones ◽  
Submarine Canyon ◽  
Tsunami Hazard ◽  
Seismic Zone ◽  
Tsunami Propagation ◽  
Content Type ◽  
Arrival Times ◽  
Tsunami Waves ◽  
Scenario Assessment ◽  
Seismic Scenarios

Purpose This paper aims to describe a multi-scenario assessment of the seismogenic tsunami hazard for Bangladesh from active subduction zones in the Indian Ocean region. Two segments of the Sunda arc, namely, Andaman and Arakan, appear to pose a tsunamigenic seismic threat to Bangladesh. Design/methodology/approach High-resolution numerical simulations of tsunami propagation toward the coast of Bangladesh have been carried out for eight plausible seismic scenarios in Andaman and Arakan subduction zones. The numerical results have been analyzed to obtain the spatial variation of the maximum tsunami amplitudes as well as tsunami arrival times for the entire coastline of Bangladesh. Findings The results suggest that the tsunami heights are amplified on either side of the axis of the submarine canyon which approaches the nearshore sea off Barisal in the seaboard off Sundarban–Barisal–Sandwip. Moreover, the computed tsunami amplitudes are comparatively higher north of the latitude 21.5o in the Teknaf–Chittagong coastline. The calculated arrival times indicate that the tsunami waves reach the western half of the Sundarban–Barisal–Sandwip coastline sooner, while shallow water off the eastern half results in a longer arrival time for that part of the coastline, in the event of an earthquake in the Andaman seismic zone. On the other hand, most parts of the Chittagong–Teknaf coastline would receive tsunami waves almost immediately after an earthquake in the northern segment of the Arakan seismic zone. Originality/value The present assessment includes probabilistic measures of the tsunami hazard by incorporating several probable seismic scenarios corresponding to recurrence intervals ranging from 25 years to over 1,000 years.

Bulgarian tsunami on 7 May 2007: numerical investigation of the hypothesis of a submarine-landslide origin

2018 ◽  
Vol 477 (1) ◽  
pp. 303-313 ◽  
Author(s):  
Oleg I. Gusev ◽  
Gayaz S. Khakimzyanov ◽  
Leonid B. Chubarov
Keyword(s):  
Black Sea ◽  
Water Resistance ◽  
Tsunami Wave ◽  
Deformable Body ◽  
Frequency Dispersion ◽  
Submarine Landslide ◽  
Generation Process ◽  
Tsunami Waves ◽  
Dispersion Effects ◽  
Dispersive Model

AbstractWe investigate the ability of a submarine landslide to generate the tsunami waves observed on the Bulgarian coast of Black Sea on 7 May 2007. In our simulations, a landslide is presented as a quasi-deformable body moving along a curvilinear slope under action of the forces of gravity, buoyancy, water resistance and bottom friction. We employ the fully non-linear weakly dispersive model for tsunami wave simulations. The computations show that the initial landslide position on the real slope is extremely important for its dynamics and the wave generation process. We constructed some model landslides which generated similar waves to those observed. Moreover, these landslides stopped in the same region. Finally, we evaluated the significance of the frequency dispersion effects in the simulations.

scholarly journals Dispersive mudslide-induced tsunamis

1998 ◽  
Vol 5 (3) ◽  
pp. 127-136 ◽  
Author(s):  
A. Rubino ◽  
S. Pierini ◽  
J. O. Backhaus
Keyword(s):  
Solitary Waves ◽  
Intermediate Phase ◽  
Water Model ◽  
Tsunami Propagation ◽  
Tsunami Waves ◽  
Open Sea ◽  
Petviashvili Equation ◽  
Wave Forms ◽  
Generation Region ◽  
Run Up

Abstract. A nonlinear nested model for mudslide-induced tsunamis is proposed in which three phases of the life of the wave, i.e. the generation, far-field propagation and costal run-up are described by means of different mathematical models, that are coupled through appropriate matching procedures. The generation and run-up dynamics are simulated through a nonlinear shallow-water model with movable lateral boundaries: in the generation region two active layers are present, the lower one describing the slide descending on a sloping topography. For the intermediate phase, representing wave propagation far from the generation region, the hydrostatic assumption is not assumed as appropriate in general and, therefore, a nonlinear model allowing for weak phase dispersion, namely a Kadomtsev-Petviashvili equation, is used. This choice is made in order to assess the relevance of dispersive features such as solitary waves and dispersive tails. It is shown that in some realistic circumstances dispersive mudslide-induced tsunami waves can be produced over relatively short, distances. In such cases the use of a hydrostatic model throughout the whole tsunami history turns out to give erroneous results. In particular, when solitary waves are generated during the tsunami propagation in the open sea, the resulting run-up process yields peculiar wave forms leading to amplified coastal inundations with respect to a mere hydrostatic context.

scholarly journals Characteristics of Global Oceanic Rossby Wave and Mesoscale Eddies Propagation from Multiple Datasets Analysis

2016 ◽  
Author(s):  
Yunfan Zhang ◽  
Fenglin Tian ◽  
Ge Chen
Keyword(s):  
Rossby Wave ◽  
Phase Speed ◽  
Mesoscale Eddies ◽  
Propagation Speed ◽  
Ocean Current ◽  
Propagation Characteristics ◽  
The North ◽  
Multiple Datasets ◽  
Salinity Data ◽  
The Relationship

Abstract. In this paper we present a research of propagation characteristics of global Rossby wave and mesoscale eddies, and we preliminarily discussing the relationship between them from multiple datasets analysis. By filtering the MSLA-H data and by means of optimized SSH method we have extracted signals of the Rossby wave, and estimated the propagation speed (zonal phase speed) of the Rossby wave and eddies. Validation for the identification of the Rossby wave also has been completed with the Argo temperature and salinity data. The prime focus covers: propagation speed comparison between the Rossby wave and the eddies, propagation characteristics in different regions. Overlaying the signals of the Rossby wave with the signatures of the eddies indicates that the Rossby wave and the eddies propagates together (westward only) in the mid-latitude, but differences appear with increasing of latitude, especially in some areas affected by ocean current, for instance, the West Wind Drift(WWD) and the North Atlantic Drift(NAD). Actually we have found that the currents led the eddies, and the Rossby wave might play an accelerative or moderative role in the eddies propagation, as a result of the velocities of the eddies and the currents were matched well, but comparison between the Rossby wave and the eddies revealed disparity. The findings are useful for understanding the relationship between the Rossby wave and mesoscale eddies.

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