Numerical Simulation Of Tsunami Propagation Research Articles

Sensitivity of slip distribution on tsunami trace heights and geological evidences: a case study of the 2011 Tohoku-Oki earthquake

We examined whether it is possible to estimate the tsunami source model of the 2011 Tohoku-Oki earthquake from a comparison of numerical simulations of tsunami propagation and sediment transport, the measured trace heights, and the sediment thickness of tsunami deposits. Twelve models with different subfault numbers were prepared based on a reference model inferred from tsunami waveform inversion. The reference model with 55 subfaults considering rupture propagation and the model with instantaneous slip successfully reproduced both the tsunami trace heights and sediment thickness distribution of tsunami deposits in the Idagawa Lowland and Sendai Plain. Other models with the same moment magnitude but fewer subfaults could not reproduce the observed trace heights, and the reproducibility of sediment thickness distribution strongly depended on the slip distribution. Models with increased slip amounts and moment magnitude could reproduce the trace heights; however, the simulated sediment thickness was underestimated for the Idagawa Lowland while overestimated for the Sendai Plain. Our results indicate that the combination of trace heights, sediment thickness of tsunami deposits, and numerical simulations of tsunami propagation and sediment transport can be used to estimate historical earthquakes and tsunamis. Efforts should be made to increase the number of subfaults for the study of historical events, although the obtained solutions may not be unique because of fewer trace heights or tsunami deposit data.

Coastal landslides in Palu Bay during 2018 Sulawesi earthquake and tsunami

In this paper, we investigate the sources for Palu Bay tsunamis, which occurred in September 2018 after a Mw 7.5 earthquake struck on a strike-slip fault. Previous land-based field studies have identified numerous coastal landslides as possible sources for tsunami generation. Here, we present new post-earthquake bathymetry survey data in the bay. We compare the new very detailed nearshore bathymetry with the pre-earthquake data so as to quantify the magnitudes and configurations of coastal landslides and the characteristics of landslide-generated waves. We perform numerical simulations of tsunami propagation, isolating the coastal landslides as the only sources. The results show that, although the landslide-generated waves characteristically have shorter periods than the observed tsunami waves, the combination of the waves is able to produce long waves comparable with those observed, due to the ringing effects of the trapped waves inside the bay. Therefore, we conclude that landslide-generated waves played a significant role in the tsunamis in Palu Bay. Nevertheless, it is likely that the tsunamis were caused by a combination of tectonic and landslide sources.

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

PurposeThis 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/approachHigh-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.FindingsThe 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/valueThe 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.

Numerical Simulation of Tsunami Propagation and Assessment of Its Impact on Dayawan Bay Nuclear Power Plant

Tsunami propagation over the entire Dayawan Bay was simulated using a 2D shallow water model to provide hydrodynamic boundary conditions for a 3D flow model, by which tsunami propagation inside the inlet of water-intake basin of the Dayawan Nuclear Power Plant (DNPP) was simulated. The 2D model covers the whole bay plus a little extension of the waters around the bay mouth. The sea side open boundary of the 2D model is generated from a superposition of an assumed tsunami process on a tide with exceedance probability of 10%. The event of encounter of a 10-min highest waters of the assumed tsunami process with such level of tide is estimated to be approximately a return period of 1490 years. Tsunami run-up in front of the revetment of the pump room was simulated using the 3D flow models. The rubble-mound breakwater was treated as porous medium in the simulation. Computational results of flow velocity indicate that tsunami propagation inside the basin is effectively prevented by the east breakwater. Computational results of waters in front of the revetment of the pump room indicate that the possible maximum water level is lower than the present elevation of the revetment, therefore the pump room has low risk of inundation.

Numerical simulation of tsunami propagation with Finite Difference Method and Runge Kutta 4th Order Method (study case : south coast of Java island)

Tsunamis are disasters that cause so much damage. In the history of the tsunami, Indonesia has been hit by tsunami several times, based on data from the National Disaster Management Agency (BNBP), as of 1629 - 2007, Indonesia was recorded 184 times affected by large and small tsunami disasters. Based on these data, it is very important for Indonesia to increase security against the tsunami disaster. Also, the tsunami in Indonesia occurred due to earthquakes, volcanic eruptions, and landslides in the sea. This study discussed about to the tsunami with a location located in the southern of Java, precisely in the area of Central Java, considering that in 2017 there was friction between the Indies and Eurasian plates which caused an earthquake measuring 6.9 magnitude, but did not cause a tsunami. In this study, a tsunami wave propagation simulation was carried out with the aim of knowing how long it would take the waves to the shoreline and how high the waves would be when they were on the shoreline. The model used is a tsunami model created by Imamura by solving differential equations using finite difference and Runge-Kutta 4th order. Based on the simulation results with the initial determination of a 5 m tsunami wave centered at a distance of 25 km from the shoreline, Tsunami waves with a height of 8.7 m will arrive at the shoreline at 140 seconds. With wave height is 8.7 m at the shoreline, the water will enter the land or can also be called the tsunami disaster. At that time, residents are expected to have been evacuated from the coastal area. In addition, based on numerical simulations that have been carried out, information is obtained that the computation time of the method is faster than the computation time of the Runge-Kutta method with differences in altitude results that are quite small and can be tolerated. This shows that the Finite Difference method can be applied to tsunami disaster mitigation software because it has a fairly fast computing time compared to the Runge-Kutta 4th order method.

Tsunami Waveforms and Runup of Undular Bores in Coastal Waters

AbstractThis paper carries out the numerical simulation of tsunami propagation based on the fully nonlinear and highly dispersive Boussinesq model. The numerical results indicate that the waveforms of a tsunami are quite different on steeply and mildly sloping beaches, which cannot be predicted by the analytical solution of the nonlinear shallow water equations. Long wave trains form on the steeply sloping beaches while undular bores emerge on the mildly sloping beaches. The simulation of hypothesized tsunamis in the China Seas provide different wave patterns in the near shore regions, including long wave trains, undular bores, and solitons. In order to study the propagation and run-up of undular bores, a series of undular bores is proposed by sinusoidal and attenuation functions. The properties of the run-up and energy budget of these undular bores are investigated.

Application of Probabilistic Tsunami Hazard Analysis for the Nuclear Power Plant Site

The tsunami hazard analysis is performed for testing the application of probabilistic tsunami hazard analysis to nuclear power plant sites in the Korean Peninsula. Tsunami hazard analysis is based on the seismic hazard analysis. Probabilistic method is adopted for considering the uncertainties caused by insufficient information of tsunamigenic fault sources. Logic tree approach is used. Uljin nuclear power plant (NPP) site is selected for this study. The tsunamigenic fault sources in the western part of Japan (East Sea) are used for this study because those are well known fault sources in the East Sea and had several records of tsunami hazards. We have performed numerical simulations of tsunami propagation for those fault sources in the previous study. Therefore we use the wave parameters obtained from the previous study. We follow the method of probabilistic tsunami hazard analysis (PTHA) suggested by the atomic energy society of Japan (AESJ). Annual exceedance probabilities for wave height level are calculated for the site by using the information about the recurrence interval, the magnitude range, the wave parameters, the truncation of lognormal distribution of wave height, and the deviation based on the difference between simulation and record. Effects of each parameters on tsunami hazard are tested by the sensitivity analysis, which shows that the recurrence interval and the deviation dominantly affects the annual exceedance probability and the wave heigh level, respectively.

Developing fragility functions for the areas affected by the 2009 Samoa earthquake and tsunami

Abstract. Fragility functions in terms of flow depth, flow velocity and hydrodynamic force are developed to evaluate structural vulnerability in the areas affected by the 2009 Samoa earthquake and tsunami. First, numerical simulations of tsunami propagation and inundation are conducted to reproduce the features of tsunami inundation. To validate the results, flow depths measured in field surveys and waveforms measured by Deep-ocean Assessment and Reporting of Tsunamis (DART) gauges are utilized. Next, building damage is investigated by visually interpreting changes between pre- and post-tsunami high-resolution satellite images. Finally, the data related to tsunami features and building damage are integrated using Geographic Information System (GIS), and tsunami fragility functions are developed based on the statistical analyses. From the developed fragility functions, we quantitatively understood the vulnerability of a coastal region in American Samoa characterized by steep terrains and ria coasts.

Time–Space Decoupled Explicit Method for Fast Numerical Simulation of Tsunami Propagation

This study presents a novel explicit numerical scheme for simulating tsunami propagation using the exact solution of the wave equations. The objective of this study is to develop a fast and stable numerical scheme by decoupling the wave equation in both the time and space domains. First, the finite difference scheme of the shallow-water equations for tsunami simulation are briefly introduced. The time–space decoupled explicit method based on the exact solution of the wave equation is given for the simulation of tsunami propagation without including frequency dispersive effects. Then, to consider wave dispersion, the second-order accurate numerical scheme to solve the shallow-water equations, which mimics the physical frequency dispersion with numerical dispersion, is derived. Lastly, the computation efficiency and the accuracy of the two types of numerical schemes are investigated by the 2004 Indonesia tsunami and the solution of the Boussinesq equation for a tsunami with Gaussian hump over both uniform and varying water depths. The simulation results indicate that the proposed numerical scheme can achieve a fast and stable tsunami propagation simulation while maintaining computation accuracy.

W041003 防災ITSによる津波情報の提供に向けた試み([W04100]機械材料・材料加工部門企画,減災・サステナブル工学の今後の展望)

This study developed a driving simulator with a tsunami inundation scenario to perform a series of experiments on evacuation by automobile drivers. To achieve the objective, the authors performed numerical simulation of tsunami propagation, and the results were visualized from the view of a driver using 3D computer graphics (CG). The CG was installed to a driving simulator, which consists of three LCDs, steering wheel, and brake and accelerator pedals. 10 examinees were employed for the driving simulator experiment, and a future plan for the experiments is proposed based on the experimental results.

A tsunami simulation of Hakata Bay using the viscous shallow-water equations

The tsunami generated by the Great East Japan Earthquake caused serious damage to the coastal areas of the Tohoku district. Numerical simulations are used to predict damage caused by tsunamis. Shallow-water equations are generally used in numerical simulations of tsunami propagation from the open sea to the coast. This research focuses on viscous shallow-water equations and attempts to generate a computational method using finite element techniques based on the previous investigations of Kanayama and Ohtsuka (Coast Eng Jpn 21:157–171, 1978). First, the viscous shallow-water equation system is derived from the Navier–Stokes equations, based on the assumption of hydrostatic pressure in the direction of gravity. Next a numerical scheme is shown. Finally, tsunami simulations of Hakata Bay and Tohoku-Oki are shown using the approach.

Estimation of Tsunami-Inundated Areas in Asahi City, Chiba Prefecture, after the 2011 Tohoku-Oki Earthquake

The 2011 off the Pacific coast of Tohoku-oki earthquake triggered an extremely large tsunami. The authors conducted a field survey in Asahi City, Chiba Prefecture, after the occurrence of the earthquake. Although located farther away from the source region of the earthquake, there was still significant damage in this area. Tsunami-inundated areas in Asahi City were identified from the map developed by disaster relief volunteers and the satellite images captured after the event. Polygons to demonstrate the tsunami-inundated areas were developed in the geographic information system. The authors compared the identified affected areas with the existing tsunami hazard map of Asahi City. The relationship between the tsunami-inundated areas and the locations of seawalls and tide-prevention forests was evaluated. In addition, a numerical simulation of tsunami propagation was performed and the ratio of totally collapsed buildings to the total number of buildings, that is, damage ratio, in terms of the estimated inundation depths was evaluated.

On sediment extent and runup of tsunami waves

Tsunami sediments play an important role in tsunami hazard assessments. Recent tsunami events and their associated tsunami deposits have produced a wealth of sediment data. Surveys of recent tsunami events observed that maximum inland tsunami inundation exceeds the maximum inland extent of sand deposition. A driving question of tsunami sedimentology is whether the difference between maximum tsunami inundation and inland extent of sand can be employed as a measure of inundation for past events for which only the extent of the sand is known. Attempts to infer the causative flow characteristics from these sediments often suffer from uncertainties in the data and from restrictive assumptions made in inversion models. The latter demonstrates that the interaction between the tsunami flow and the movable bed is not fully understood. In our contribution, we employ numerical simulations of tsunami propagation and inundation with MOST and a simple model for deposition. In our simulations, we vary the onshore slope, the initial amplitude, which can be interpreted as offshore wave amplitude, and the grain size. While the initial amplitude and onshore slope influence the difference between maximum inundation and sand extent, the grain size has little effect. The link between the onshore slope, initial amplitude and the difference between the maximum tsunami inundation and inland sediment extent can be employed as a first-order quantitative tool to estimate tsunami flow characteristics and maximum inundation from tsunami deposits. We anticipate these results will improve tsunami hazard assessments and narrow the gap between field observations and numerical simulations.

Tsunami run-up associated with co-seismic thrust slip produced by the 2011 Mw 9.0 Off Pacific Coast of Tohoku earthquake, Japan

The 2011 Mw 9.0 Off Pacific Coast of Tohoku (Japan) earthquake generated a violent tsunami and unexpected high tsunami wave that caused great substantial damage and ∼18,940 fatalities along the east–northeast coast of Honshu Island of Japan. Analyses of high-resolution remote sensing imagery data acquired before and after the earthquake, combined with the results of field investigations, reveal that (i) run-up height of the tsunami (i.e., the inland limit of tsunami) was spatially variable, ranging from <3m to ∼35m, and (ii) large run-up heights occurred mainly in the areas between Ishinomaki (∼38.2°N) and Miyako city (∼40.2°N), close to the epicenter of 2011 Mw 9.0 earthquake, and showed a gradual decrease away from this region. Combined with the ground motion direction revealed by GPS and seismic data, the distribution of run-up height is consistent with that of ground displacement (calculated from GPS observations) and that of co-seismic thrusting slip on the source fault plane along the plate boundary (calculated from the seismic inversion). The results of numerical simulation of tsunami propagation show that (i) the distributions of tsunami height along the northeast Honshu coastline are constrained mainly by thrusting slip on the source fault plane; and (ii) the height of tsunami wave in special areas was strongly affected by the sawtooth geometry of the coastline.

Nearshore tsunami amplitudes off Sri Lanka due to probable worst-case seismic scenarios in the Indian Ocean

This paper describes a deterministic assessment of the tsunami hazard to Sri Lanka from all active subduction zones in the Indian Ocean Basin. High resolution numerical simulations of tsunami propagation have been carried out for eight plausible maximum-credible seismic scenarios in Northern Sumatra–Andaman, Southern Sumatra, Arakan and Makran subduction segments. The numerical results have been analyzed to obtain wave arrival times and maximum tsunami amplitudes just off the coastline of Sri Lanka. A sensitivity analysis carried out at the outset indicates that the computed tsunami amplitudes off Sri Lanka are only marginally sensitive to the perturbations in the source parameters. Moreover, the computed values of peak tsunami amplitudes and arrival times corresponding to an event similar to the tsunami in 2004 are in good agreement with the respective field observations. The numerical simulations also suggest that the maximum tsunami amplitudes around the coastline of Sri Lanka corresponding to worst-case scenarios in Southern Sumatra, Arakan and Makran seismic zones are only less than about 20–30% of those due to the same in Northern Sumatra–Andaman segment. This means that an event similar to the 2004 tsunami in the Northern Sumatra–Andaman subduction zone could be considered as the worst-case seismogenic tsunami scenario for any part of the coastline of Sri Lanka. The information presented in this paper would help authorities responsible for evacuation to make a better judgement as to the level of probable maximum tsunami heights in different areas along the coastline of Sri Lanka, and act accordingly, if a large earthquake were to occur in any of the subduction zones in the Indian Ocean Basin.

High grid resolution and parallelized tsunami simulation with fully nonlinear Boussinesq equations

Numerical simulation of tsunami propagation in large basin across the ocean demands significantly high computational capability in terms of CPU time and memory allocation. Due to this limitation, the use of sequential codes in a single scientific workstation is possible only for small-scale tsunami problem. To overcome this difficulty, a parallel Boussinesq wave model is developed based on the original FUNWAVE sequential model for efficient simulation of long wave propagation, coastal inundation and runup. The numerical resolution is decomposed into small sub-domains using domain decomposition technique for each processor to perform the calculations. The wave information is exchanged between processors via message passing interface (MPI). We show the effectiveness of this parallel code on distributed- and shared-memory computer clusters in simulating two tsunami events: the 2004 Indian Ocean and the 1999 Vanuatu tsunamis. Communication in the overlapping domains and load balancing in the partitioned domains are considered to ensure the efficiency of this method. It is found that the performance of the parallel model for both large- and small-scale tsunami problems is very satisfactory. Finally, the parallel model is applied to a spatial hierarchical grids methodology for a location-specific numerical simulation. Grid sensitivity and improved simulation results for runups along Phang Nga coastline from Takua Thung to Khao Lak are presented.

Field measurements and numerical simulations of the 2004 tsunami impact on the south coast of Sri Lanka

This paper examines the factors that have contributed to the significant spatial variability of the impact of the December 2004 tsunami in the southern province of Sri Lanka. Documented observations of the evidence left behind by the 2004 tsunami together with numerical simulation of tsunami propagation have been utilized for this purpose. The field data examined in the present analysis comprise the maximum water levels, the horizontal inundation distances and the number of housing and other buildings damaged as a result of the 2004 tsunami whilst the numerical results considered include the distribution of the amplitude of the tsunami. The present model results confirm that source directivity controls the distribution of tsunami amplitudes farther offshore whilst large-scale bathymetric features significantly influence the tsunami propagating over the shelf. Our analyses of field data also show the dominant influence of coastal geomorphology and topography on the extent of tsunami inundation.

Numerical simulation of tsunami propagation using the characteristic-based split method

Numerical simulation of tsunami propagation using the characteristic-based split method

A Study for the Sediment Transport due to Tsunami along the Natural Coast

In this study, we investigated the sediment transport due to the 2004 Indian ocean tsunami along the natural coast at Hambantota, Sri-lanka. Bathymetry and topography surveys before and after the tsunami were conducted and the results showed significant erosion by the tsunami, especially around the places where shoreline discontinuations were observed. We conducted a numerical simulation of tsunami propagation as well as the bathymetry change induced by the tsunami. Furthermore, we also estimated the bathymetry change due to the usual sea waves at the coast. Our numerical results suggested that the tsunami has strong bottom shear stress at specific landform such as a river mouth and a cape. We also found that the sediment erosion and accumulation due to the tsunami had been mitigated by usual sea waves after the tsunami.

Characteristic period of Tsunami in Seto Inland Sea

It is very important for tsunami disaster prevention in the coastal area of Shikoku Island to clarify a mechanism of tsunami propagation in the Seto Inland Sea. Especially, a resonance of tsunami is a dominant factor in such a narrow inland sea. In this study, numerical simulation of tsunami propagation is executed to estimate tsunami height and characteristic period in the Seto Inland Sea. According to the numerical analysis, a tsunami height does not decline during about 10 hours and a characteristic period of Harima-nada is about 60 minutes. The tsunami continued to be resonated for more than 20 hours in the Seto Inland Sea.