Numerical Simulation Of Tsunami Research Articles

Experimental and numerical investigation of tsunami behavior around two upright sea dikes with different heights

ABSTRACT The 2011 Tohoku Tsunami caused severe damage to many coastal defenses along the Japanese coastline, including areas where two adjacent upright sea dikes of different heights met. There are many places along the coastline where structures of different heights and shapes meet due to the various design codes. In this study, the authors aim to examine the tsunami flow around such dikes by conducting three-dimensional hydraulic experiments in a tsunami wave basin and numerical simulations using the fluid dynamics model OpenFOAM. Twelve experimental cases were tested by changing the waveforms, and also by keeping the height of one side of the dike model constant while adjusting the dimensions of the other side. The results show that the difference in height between the structures significantly influences the volume of overtopping over the relatively lower dike and the inundation depth and velocity behind the dikes. Furthermore, different characteristics of inundation patterns are observed between the inundation depth and velocity. Hence, this study illustrates the necessity to re-assess the effectiveness of such structures against tsunami events.

Local tsunami run-up depending on initial localization of the landslide body at submarine slope

The numerical simulation of tsunami induced by layer-by-layer sliding of submarine slope with various initial location of landslide body is performed. For the landslide body, an elastoplastic model with layered sediments taking into account the porosity and deconsolidation of the landslide mass, resting on a relatively rigid base, is used. The characteristic parameters of the above model correspond to those of the landslide and tsunami event in the Corinth Bay on February 7, 1963 modeled by the authors (Papadopoulos et al. 2007). To numerically represent the dynamics of landslide motion numerical code FLAC is used, which in contrast to the finite element method implements an explicit finite-difference scheme for solving three-dimensional problems of continuum mechanics, and allows simulation of the nonlinear behavior of porous-saturated grounds under conditions of plastic flow above the yield stress. Because of plane slope conditions, the nonlinear system of shallow water equations is used for the numerical simulation of tsunami. The results demonstrate that at each time moment, the tsunami runup occurs at novel surface of the coastal slope that leads to complex repositioning of the shoreline point that depends on initial location of the landslide volume. Such an observation is absent in conventional (e.g. rigid block, viscoplastic etc.) models The results of the work demonstrate a rather physical picture of the process under consideration. More importantly modeling results of this work may help in identifying the generating mechanism of historical or future landslide tsunamis.

Uncertainty of probabilistic tsunami hazard assessment of Zihuatanejo (Mexico) due to the representation of tsunami variability

ABSTRACT This study conducts a probabilistic tsunami hazard assessment (PTHA) and compares two approaches to representing earthquake source variability in the PTHA. The target region is the coast of Zihuatanejo in the State of Guerrero, Mexico. First, numerous synthetic fault slip distributions are generated using a stochastic random-phase process. The moment magnitude ranges from 7.8 to 8.6. A numerical tsunami simulation is implemented for each earthquake fault slip. The result of the Monte Carlo simulation indicates the tsunami heights at the nearshore of city areas tend to be higher. Then, the exceedance probabilities of tsunami height are estimated and compared using two different PTHA approaches: the random phase approach and the logic tree approach. The logic tree can generally incorporate many types of uncertainty, but this study focuses on the earthquake source uncertainty for comparison. The comparison result indicates significant differences between the two tsunami hazard models. Additionally, the logic tree approach is used to investigate the possible ranges in tsunami heights for extreme events by assuming that a sizable epistemic uncertainty exists in a given region. The tsunami heights for a 1,000-year event vary significantly when the weighting values for the paths in the logic tree are changed.

Determination of Source Models Appropriate for Tsunami Forecasting: Application to Tsunami Earthquakes in Central Sumatra, Indonesia

In the subduction zone off the west coast of central Sumatra, two great earthquakes, the 2007 great Bengkulu earthquake (Mw 8.4) and the 2010 Mentawai tsunami earthquake (Mw 7.8), occurred along the plate interface. Although the moment magnitude of the 2010 earthquake was much smaller than that of the 2007 earthquake, the tsunami heights resulting from the former 2010 earthquake were higher than those resulting from the latter 2007 earthquake, indicating that tsunami heights are difficult to forecast. An advanced method for determining appropriate source models that can explain the tsunami heights along coastal areas is needed for tsunami warning purposes. In this study, fault parameters were estimated from the W-phase inversion, and fault length and width were calculated from suitable scaling relations between those and the magnitude for the 2007 and 2010 earthquakes. Tsunami numerical simulations were conducted using various slip amounts or corresponding rigidities. The best slip amount or corresponding rigidity was selected by comparing the measured and computed tsunami heights. For the 2007 Bengkulu earthquake, the measured tsunami heights are well explained using a rigidity of 3.0 × 1010 Nm−2 (7.59-m slip amount). For the 2010 Mentawai tsunami earthquake, the measured tsunami heights are well explained using a rigidity of 1.5 × 1010 Nm−2 (8.17-m slip amount). From those results, we determined the depth-dependent rigidity relation for Central Sumatra to estimate appropriate source models in our tsunami height forecasting method.

Evidence of giant earthquakes and tsunamis of the seventeenth-century type along the southern Kuril subduction zone, eastern Hokkaido, northern Japan: a review

Abstract Large earthquakes of magnitude 7–8 occur at intervals of about 70–100 years in the southern Kuril Trench off eastern Hokkaido, northern Japan. However, especially large giant earthquakes (M w c. 8.8) have recurred at 300–500 year intervals, and the most recent of these was in the early seventeenth century. Surveys on the Pacific coast of eastern Hokkaido have documented field evidence that includes sharp contacts of peat and mud layers, indicative of coseismic coastal uplift, and large tsunami sand layers. Several proposed fault models of the seventeenth-century giant earthquake have been tested with numerical tsunami simulations. The best of these models incorporates a multi-segment interplate earthquake (M w 8.8) with large slip near the trench axis. The seventeenth-century giant earthquake and the 1611 Keicho Sanriku tsunami appear to have had different sources because varve counts from Lake Harutori suggest that the seventeenth-century giant earthquake occurred at c. 1637. Moreover, a consideration of regional tectonics suggests that convergence of the Kuril forearc sliver controls the current topography of eastern Hokkaido. Further progress in understanding the seismicity of this region will benefit from the combined insights of both geologists and seismologists.

Today in Thailand: multidisciplinary perspectives on the current tsunami disaster risk reduction

Abstract Thailand is one of the many countries in Asia that fell victim to the monstrous 2004 Indian Ocean tsunami. To date, there has been tons of effort to reduce disaster risk in Thailand. Nevertheless, there is still a considerable margin for improvement. This paper aims to review previous efforts and measures that have been taken to reduce Thailand's risk to disasters, and highlight possible areas for improvement. We use the disaster risk management as a thought-framework for our review, where we discuss Thailand's current disaster risk reduction (DRR) measures from a multi-perspective: the tsunami numerical simulation, tsunami warning system, tsunami evacuation sign, manuals and guidelines, evacuation shelters, housing recovery, hotel business and recovery, public awareness and media, and disaster education. In understanding the current state of disaster risk efforts, we will then highlight potential areas for improvement.

Two-dimensional numerical simulations of tsunamis on Puger beach, Jember

On June 3, 1994, an earthquake located 200 km south of the island of Java triggered a devastating tsunami and caused losses of life and materials around beaches in the Jember, Lumajang, and Banyuwangi Regencies. It is highly important to study the process of tsunami occurrences, especially at Puger Beach, Jember. Thus, the main purpose of this study is to understand the mechanism of tsunamis in Puger Beach. Tsunami numerical simulation was performed using the Delft3D model to calculate the propagation of possible future tsunamis. Bathymetric data obtained from GEBCO_08 were utilized in this study. The tsunami model was validated using the survey data of the tsunami on June 3, 1994. Tsunami simulations were successfully performed in this study. From numerical simulations, it was shown that the fault model characteristics utilized in the model directly affected the tsunami height. Just after the initial surface elevation, the wave height decreased and the tsunami propagated at sea. As the wave propagated from offshore to shallower area, the tsunami height increased until reaching the maximum tsunami height in coastal areas such as Puger Beach. Tsunami mechanisms are clarified from both numerical simulations.

1640年北海道駒ヶ岳噴火による津波堆積物の分布と津波規模の推定

1640年北海道駒ヶ岳噴火による津波堆積物の分布と津波規模の推定

Study on boundary layer development and bottom shear stress beneath a tsunami

ABSTRACTThis paper presents a detailed investigation on unsteady effects in bottom boundary layer beneath a tsunami. In numerical simulation of tsunami, bottom shear stress has commonly been evaluated by using steady flow friction laws such as Manning equation, simply assuming that long-period wave motion satisfies quasi-steady flow conditions. However, the present study found that the behavior of tsunami-induced bottom boundary layer has an unsteady characteristics and acts similar to that induced by wind-generated waves even under long-period wave motion. As a result, bottom shear stress under tsunami is much larger than the estimation using steady friction coefficient due to a steep velocity gradient in the bottom boundary layer. Surprisingly, the steady flow friction law is not valid in almost the entire computational domain, from the source area to shallow region. This result highly coincides with the field measurement data obtained by Lacy group during the 2010 Chilean Tsunami at the Monterey Bay mouth in U.S. A correction coefficient is proposed to take into account unsteady effects in the conventional estimation method using a steady friction factor; this approach is validated by comparing with numerical simulation results using k-ω turbulence model.

Influence of Elevation Data Resolution on Tsunami Loss Estimation and Insurance Rate-Making

Tsunamis triggered by large offshore earthquakes are devastating, and buildings located near the coast experience damage and loss due to such extreme events. In evaluating regional tsunami impact via numerical tsunami simulations, it is important to pay close attention to local geographical features represented by a digital elevation model (DEM), because tsunami loss estimation is sensitive to its quality and resolution. This study investigates the influence of elevation data resolution on tsunami loss estimation at different scales by comparing tsunami risk results using DEMs of four resolutions (i.e. 10-m, 50-m, 150-m, and 450-m). Using stochastic tsunami modelling, a case study is carried out by focusing on the Tohoku region in Japan to investigate the influence of DEM resolution on tsunami loss estimation considering the effect of location attributes (i.e. coastal topography, distance from the coast, and land elevation) for two building portfolios on plain coast and ria coast. The results indicate the significance of DEM resolution for local tsunami loss estimations at different locations. The local tsunami risk is closely related to the building location, and the increase of distance from the coast and/or land elevation dramatically reduces the local tsunami risk. The investigations extend discussions regarding the calculations of pure insurance premium rate for tsunami loss coverage depending upon structural attributes and location attributes.

Archiving Disaster Remains: The Case of ”Sasanao Factory” in Yuriage Village, Natori City, Miyagi Prefecture

In the areas affected by the 2011 Great East Japan tsunami, some damaged buildings were proposed to be preserved as “Disaster Remain” to share this experience and educating future generations. However, many these potential buildings were eventually demolished. This study aims to provide an alternative and eventually a consensus among communities that faced conflicts over the preservation or destruction of such disaster buildings. The methodology consists of 3D building modelling, tsunami numerical simulation and recording tsunami evacuation behaviour with interview survey. In sum, this practical study of “Sasanao Factory” demonstrates that the archiving of disaster remain can offer a compromise between those who wish to preserve disaster ruins, here the owner of the building, and those who want or need their destruction, here local government.

Source Models of the 2012 Haida Gwaii (Canada) and 2015 Illapel (Chile) Earthquakes and Numerical Simulations of Related Tsunamis

Seismological observations provide essential input parameters for numerical tsunami simulations. Here, we present source mechanism parameters, finite-fault source rupture models and numerical tsunami simulation results for the destructive October 28, 2012 Haida Gwaii-Canada (Mw 7.7) and September 16, 2015 Illapel-Chile (Mw 8.3) earthquakes and resulting tsunamis. These two earthquakes were controlled by active tectonic features along the subduction zones that had developed in response to the convergent movements of lithospheric plates. The faulting geometry (strike, dip, and rake angles), focal depth, fault dimensions, average and maximum slip values on the fault planes and seismic moments of the earthquakes are estimated by analyzing teleseismic long-period P- and SH-waves and broadband P-waveforms and using waveform inversion and hybrid back-projection methods. The obtained slip models of the earthquakes reveal heterogeneous slip distributions on fault planes with long source durations (~ 80 s and 150 s) and low stress drop values (10–15 bars). Numerical simulations of tsunami wave propagation are further performed using the uniform and non-uniform slip models and nonlinear long-wave equations in spherical coordinates. The shape and arrival times of leading tsunami waves are adequately constrained particularly with the heterogeneous slip distribution models. The general characteristics of synthetic tsunami waveforms (e.g., amplitude, shape, arrival time) calculated using the non-uniform slip model, are more consistent with the observed tsunami records than those of a uniform slip model. It is further seen that simulation results using preliminary and fast slip models for both earthquakes give only approximate early tsunami estimates; tsunami wave heights and arrival times to the coasts are mostly not well simulated. The results indicate that tsunami simulations based on finite-fault source slip models likely contribute to the determination of tsunamigenic coastal regions by revealing locations, arrival times, amplitudes, and directions of tsunami waves within a close approximation to observed records off-shore and far from the source region. They provide sufficient information to facilitate tsunami warning and mitigation challenges after the destructive earthquakes. We further suggest that joint inversions of GPS, tsunami, teleseismic and strong ground motion records and higher resolution bathymetry data are needed in order to obtain better correlations between observed and synthetic tsunami data, especially for the later arriving waves.

Numerical Simulation of Tsunami in the Black Sea Caused by the Earthquake on September 12, 1927

Numerical Simulation of Tsunami in the Black Sea Caused by the Earthquake on September 12, 1927

Chislennoe modelirovanie tsunami v Chernom more, vyzvannogo zemletryaseniem 12 sentyabrya 1927 g.

Chislennoe modelirovanie tsunami v Chernom more, vyzvannogo zemletryaseniem 12 sentyabrya 1927 g.

New Building Damage Assessment Method Based on Numerical Tsunami Simulation and Analytical Force Estimation: Case study of the 2011 Tohoku tsunami

New Building Damage Assessment Method Based on Numerical Tsunami Simulation and Analytical Force Estimation: Case study of the 2011 Tohoku tsunami

Assessment of the tsunami hazard on Moroccan coasts using numerical modeling

Caused by earthquakes in the marine environment, tsunamis are often of particular violence. Pests, their damage far exceeds those caused by earthquakes earthquakes. In Morocco, seismic sensors in the national network often detect earthquakes in the marine environment. However, specialists minimize their threat given the peculiarity of the Moroccan ocean zone. The latter is characterized by the importance of the length of the faults and the depth of the seismic focus.This work can be considered as a first approach to the study and understanding tsunamis. Although Morocco has known since historical times, earthquakes and tsunamis along its coasts.This preliminary study is mainly intended to show the contribution of the numerical simulation of tsunamis, with a concrete application of the 1755 Tsunami of Lisbon based on the four source zones involving the five potentially tsunamigenic faults that are generally mentioned in the literature for this major event.

Tsunami Source Inversion Using Tide Gauge and DART Tsunami Waveforms of the 2017 Mw8.2 Mexico Earthquake

On September 8, 2017 (UTC), a normal-fault earthquake occurred 87 km off the southeast coast of Mexico. This earthquake generated a tsunami that was recorded at coastal tide gauge and offshore buoy stations. First, we conducted a numerical tsunami simulation using a single-fault model to understand the tsunami characteristics near the rupture area, focusing on the nearby tide gauge stations. Second, the tsunami source of this event was estimated from inversion of tsunami waveforms recorded at six coastal stations and three buoys located in the deep ocean. Using the aftershock distribution within 1 day following the main shock, the fault plane orientation had a northeast dip direction (strike = 320^{circ }, dip = 77^{circ }, and rake =-92^{circ }). The results of the tsunami waveform inversion revealed that the fault area was 240 km × 90 km in size with most of the largest slip occurring on the middle and deepest segments of the fault. The maximum slip was 6.03 m from a 30 × 30 km2 segment that was 64.82 km deep at the center of the fault area. The estimated slip distribution showed that the main asperity was at the center of the fault area. The second asperity with an average slip of 5.5 m was found on the northwest-most segments. The estimated slip distribution yielded a seismic moment of 2.9 times 10^{21} Nm (Mw = 8.24), which was calculated assuming an average rigidity of 7times 10^{10} N/m2.

Tsunami hazard evaluation for Kuwait and Arabian Gulf due to Makran Subduction Zone and Subaerial landslides

Given the recent historical disastrous tsunamis and the knowledge that the Arabian Gulf (AG) is tectonically active, this study aimed to evaluate tsunami hazards in Kuwait from both submarine earthquakes and subaerial landslides. Despite the low or unknown tsunami risks that impose potential threats to the coastal area’s infrastructures and population of Kuwait, such an investigation is important to sustain the economy and safety of life. This study focused on tsunamis generated by submarine earthquakes with earthquake magnitudes (M w ) of 8.3–9.0 along the Makran Subduction Zone (MSZ) and subaerial landslides with volumes of 0.75–2.0 km3 from six sources along the Iranian coast inside the AG and one source at the Gulf entrance in Oman. The level of tsunami hazards associated with these tsunamigenic sources was evaluated using numerical modeling. Tsunami model was applied to conduct a numerical tsunami simulation and predict tsunami propagation. For landslide sources, a two-layer model was proposed to solve nonlinear longwave equations within two interfacing layers with appropriate kinematic and dynamic boundary conditions. Threat level maps along the coasts of the AG and Kuwait were developed to illustrate the impacts of potential tsunamis triggered by submarine earthquakes of different scales and subaerial landslides at different sources. GEBCO 30 arc-second grid data and others were used as bathymetry and topography data for numerical modeling. Earthquakes of M w 8.3 and M w 8.6 along the MSZ had low and considerable impacts, respectively, at the Gulf entrance, but negligible impacts on Kuwait. An earthquake of M w 9.0 had a remarkable impact for the entire Gulf region and generated a maximum tsunami amplitude of up to 0.5 m along the Kuwaiti coastline 12 h after the earthquake. In the case of landslides inside the AG, the majority impact occurred locally near the sources. The landslide source opposite to Kuwait Bay generated the maximum tsunami amplitudes reaching 0.3 m inside Kuwait Bay and 1.8 m along the southern coasts of Kuwait.

Method to Determine Appropriate Source Models of Large Earthquakes Including Tsunami Earthquakes for Tsunami Early Warning in Central America

Large earthquakes, such as the Mw 7.7 1992 Nicaragua earthquake, have occurred off the Pacific coasts of El Salvador and Nicaragua in Central America and have generated distractive tsunamis along these coasts. It is necessary to determine appropriate fault models before large tsunamis hit the coast. In this study, first, fault parameters were estimated from the W-phase inversion, and then an appropriate fault model was determined from the fault parameters and scaling relationships with a depth dependent rigidity. The method was tested for four large earthquakes, the 1992 Nicaragua tsunami earthquake (Mw7.7), the 2001 El Salvador earthquake (Mw7.7), the 2004 El Astillero earthquake (Mw7.0), and the 2012 El Salvador–Nicaragua earthquake (Mw7.3), which occurred off El Salvador and Nicaragua in Central America. The tsunami numerical simulations were carried out from the determined fault models. We found that the observed tsunami heights, run-up heights, and inundation areas were reasonably well explained by the computed ones. Therefore, our method for tsunami early warning purpose should work to estimate a fault model which reproduces tsunami heights near the coast of El Salvador and Nicaragua due to large earthquakes in the subduction zone.

Preliminary Study on Long-Term Flooding After the Tsunami

After the Nankai earthquake in 1946, the resultant flooding lasted for a long time, because seawater remained on land after the tsunami in Kochi city. Large-scale flooding occurred in Ishinomaki city immediately after the Great East Japan Earthquake in 2011. Long-term flooding may hamper disaster responses such as rescue and recovery activities. This paper studied the risks of long-term flooding after the Nankai earthquake in Tokushima city based on a paleographical survey and numerical analysis. The paleographical survey identified statements such as “seawater sometimes flowed onto the land at the full tide,” suggesting occurrences of long-term flooding after previous Nankai earthquakes. The numerical analysis separately calculated values inside and outside the levee. The tsunami waveforms outside the analysis area obtained by tsunami numerical simulation was used as the boundary condition of the inland flow modeling, that is water was introduced inside the levee when the tsunami water level exceeded the upper end of the levee. The two layers of ground surface and the drain were defined to calculate the flow, including water exchange between the two layers, and the water was drained forcefully outside the levee using a drainage pump. The possibility of long-term flooding in the analysis area is suggested when a large-scale earthquake occurs in the Nankai trough.