Numerical Simulation Of Tsunami Research Articles

Analysis of Tsunami Characteristics of Korea Southern Coast Using a Hypothetical Scenario

Large-scale earthquakes are occurring globally, especially in the South Asian crust, which is experiencing a state of tension in the aftermath of the 2011 East Japan Earthquake. Uncertainty and fear regarding the possibility of further seismic activity in the near future have been on the rise in the region. The National Disaster Management Research Institute has previously studied and analyzed the overflow characteristics of a tsunami and the rate of flood forecasting through tsunami numerical simulations of the East Sea of South Korea. However, there is currently a significant lack of research on the Southern Coast tsunamis compared to the East Coast. On the Southern Coast, the tidal difference is between 1~4 m, and the impact of the tides is hard to ignore. Therefore, it is necessary to analyze the impact of the tide propagation characteristics on the tsunami. Occurrence regions that may cradle tsunamis that affect the southern coast region are the Ryukyu Island and Nankai Trough, which are active seafloor fault zones. The Southern Coast has not experienced direct damage from tsunamis before, but since the possibility is always present, further research is required to prepare precautionary measures in the face of a potential event. Therefore, this study numerically simulated a hypothetical tsunami scenario that could impact the southern coast of South Korea. In addition, the tidal wave propagation characteristics that emerge at the shore due to tide and tsunami interactions will be analyzed. This study will be used to prepare for tsunamis that might occur on the southern coast through tsunami hazard and risk analysis.

Cascading events during the 1650 tsunamigenic eruption of Kolumbo volcano

Volcanic eruptions can trigger tsunamis, which may cause significant damage to coastal communities and infrastructure. Tsunami generation during volcanic eruptions is complex and often due to a combination of processes. The 1650 eruption of the Kolumbo submarine volcano triggered a tsunami causing major destruction on surrounding islands in the Aegean Sea. However, the source mechanisms behind the tsunami have been disputed due to difficulties in sampling and imaging submarine volcanoes. Here we show, based on three-dimensional seismic data, that ~1.2 km³ of Kolumbo’s northwestern flank moved 500–1000 m downslope along a basal detachment surface. This movement is consistent with depressurization of the magma feeding system, causing a catastrophic explosion. Numerical tsunami simulations indicate that only the combination of flank movement followed by an explosive eruption can explain historical eyewitness accounts. This cascading sequence of natural hazards suggests that assessing submarine flank movements is critical for early warning of volcanogenic tsunamis.

Numerical simulation of tsunami in the system of sevastopol bays

Within the framework of numerical simulation, a study was made of the penetration of tsunami waves into the system of Sevastopol bays. The non-linear SWASH hydrodynamic model was used to simulate the tsunami propagation. To determine the boundary conditions on the liquid boundary of the computational domain, using the Black Sea tsunami model, the level fluctuations near Sevastopol in the region of depths of 90 m were calculated during the passage of tsunami waves from three potential tsunami foci caused by underwater earthquakes of magnitude 7. It was found that in because of tsunami penetration into the bays of Sevastopol from the nearest focus, the rise in sea level in the tops of the bays could reach 1–2 m. The maximum amplitudes of level fluctuations were received in Pesochnaya and Karantinnaya bays, where they reached 2 m. In the Sevastopol Bay, the level rises were about 0.5–1 m. The most intense fluctuations were observed in the first 3–3.5 hours of the tsunami action. It is shown that the coastal zone of Sevastopol is protected from waves coming from distant foci by Cape Сhersones. Numerical experiments have shown that the protective piers at the entrance to the Sevastopol Bay do not have a significant effect on the sea level fluctuations caused by the tsunami inside the bay.

Tsunami evacuation sites in the northern Sumatra (Indonesia) determined based on the updated tsunami numerical simulations

In many parts of tsunami prone areas, providing tsunami evacuation structures is often regarded as costly and difficult to manage, whereas several existing building and hills can be introduced as tsunami evacuation sites. This research intends to introduce practical and scientific methods in assessing the feasibility of hills and buildings for vertical tsunami evacuation facilities. Here, the aim is to combine tsunami numerical simulations and field assessment to determine suitable hills and buildings as vertical tsunami evacuation facilities in Calang and Banda Aceh (Indonesia) that were severely destroyed by the 2004 Indian Ocean tsunami. The numerical simulations were based on the latest condition of land cover of the study area, which has changed significantly in the last 20 years. Using the newly updated land cover, the tsunami model reveals that the tsunami estimated maximum height is 13 m in Calang. The existing buildings and hills, with an altitude higher than tsunami heights, which can be reached within 30 min (15 min less than the minimum tsunami arrival times) from the centres of the villages, are proposed as tsunami evacuation sites. In Banda Aceh and Calang, 10 public buildings, 13 mosques, and 4 hills are proposed as alternative escape sites.

Analysis of the Extreme Tsunami Risk to Sanya New Airport in the South China Sea

The Manila trench in the South China Sea (SCS) is identified as being most susceptible to the future major earthquakes. Once a submarine earthquake occurs, the coastal areas and ocean engineering projects around SCS will be affected. Based on the Sanya new airport project, this paper presents an analysis of tsunami impacts to the project region. A series of numerical simulations of tsunami are carried out and compared under different magnitudes of earthquakes. An extreme tsunami induced by a giant earthquake of M9.3 is simulated and analyzed in detail. The tsunami propagation scenarios and surface elevation in the region are presented. The inundation map and flow velocity distribution are analyzed. The impacts of this human project to the coasts are discussed by comparing tsunami wave height with and without the artificial island. According to the numerical results and relevant analysis, the giant tsunami will have great impacts to the artificial island.

Numerical simulation of landslide-generated tsunamis in lakes: A case study of the Xiluodu Reservoir

Numerical simulation of landslide-generated tsunamis in lakes: A case study of the Xiluodu Reservoir

Spatial Extent of Mid‐To Late‐Holocene Sedimentary Record of Tsunamis Along the Southern Kuril Trench, Hokkaido, Japan

AbstractWith their complex cycles and rupture modes, infrequent megathrust earthquakes require a high‐resolution spatiotemporal record of tsunami inundations over thousands of years to provide more accurate long‐term forecasts. The geological record suggests that Mw > 8 earthquakes in the Kuril Trench occurred at intervals of several hundred years. However, uncertainties remain regarding the rupture zone, owing to the limited survey areas and chronological data. Therefore, we investigated the tsunami deposits in a coastal wetland of southeastern Hokkaido, Japan, to characterize the tsunamis that originated from the Kuril Trench over the last 4,000 years. On the Erimo coast, more than seven sand layers exhibited common features of tsunami deposits, such as sheet distributions of several hundred meters, normal grading structures, and sharp basal contacts. According to numerical tsunami simulations, the 17th‐century sand layer could be reproduced using a multiple rupture zone model (Mw ∼ 8.8). We used high‐resolution radiocarbon dating and tephras to correlate the tsunami deposits from the last 4,000 years with those reported from regions ∼100 km away. The tsunami history revealed here shows good agreement with the histories of adjacent regions. However, the paleotsunamis reported to have occurred in regions >200 km away include events that differ from those in this study, suggesting a diversity of Mw > 8 earthquakes in the Kuril Trench. We clarified the history and extents of earthquake‐generated tsunamis along the southwestern end of the Kuril Trench, which were previously unknown. Our results provide a framework for magnitude estimations and long‐term forecasts of earthquakes.

Tsunami Early Warning System Based on Maritime Wireless Communication

Tsunami buoy, linked to satellite, is commonly used as a tsunami early warning system but has been discovered to have several drawbacks such as the need for approximately 5 minutes to issue an early warning for a tsunami after detecting the initial wave as well as its fragility. It was also reported that the twenty-two buoys placed in the Indonesian seas from 2012 to 2018 were damaged and missing. Therefore, this study proposes a new method for tsunami early warning by integrating ship-to-ship maritime wireless communication. It is important to note that vessels or fishing boats with over 30 GT have the ability to travel more than 100 nmi (approximately 180 km) from the shoreline and can be equipped with point-to-multipoint VHF radio communication. Meanwhile, smaller boats on the fishing ground located approximately 2-5 km from the shore can use a WiFi network to communicate like a wireless mesh while the existing terrestrial network can be used for the ship-to-shore communication between boats and land stations. This system is expected to provide significant benefits for a fishing town such as Pangandaran, West Java, Indonesia which is directly facing Java Megathrust in the Indian Ocean. Therefore, a tsunami numerical simulation was conducted in this study using Shallow Water Equation which involved a hypothetical tsunami simulated from the possible fault source which is approximately 250 km from the source. Moreover, the vessel’s location was assumed to be in line with the fishing ground while the arrival time of the tsunami was estimated from the model to be 22.5 minutes and compared to the relay time of the proposed system which was approximately 5.4 seconds. This is faster in terms of delay than the existing system which relays information through satellite at approximately 5 minutes in an ideal condition and also has the ability to reduce the need for tsunami buoys.

Reexamination of tsunami source models for the twentieth century earthquakes off Hokkaido and Tohoku along the eastern margin of the Sea of Japan

Large earthquakes around Japan occur not only in the Pacific Ocean but also in the Sea of Japan, and cause both damage from the earthquake itself and from the ensuing tsunami to the coastal areas. Recently, offshore active fault surveys were conducted in the Sea of Japan by the Integrated Research Project on Seismic and Tsunami Hazards around the Sea of Japan (JSPJ), and their fault models (length, width, strike, dip, and slip angles) have been obtained. We examined the causative faults of M7 or larger earthquakes in the Sea of Japan during the twentieth century, comprising events of 1940, 1964, 1983, and 1993, using seismic and tsunami data. The 1940 off Shakotan Peninsula earthquake (MJMA 7.5) appears to have been caused by the offshore active faults MS01, MS02, ST01, and ST02 as modeled by the JSPJ. The 1993 off the southwest coast of Hokkaido earthquake (MJMA 7.8) likely occurred on the offshore active faults OK03a, OK03b, and OK05, while the 1983 Central Sea of Japan earthquake (MJMA 7.7) probably related to MMS01, MMS04, and MGM01. For these earthquakes, the observed tsunami waveforms were basically reproduced by tsunami numerical simulation from the offshore active faults with the slip amounts obtained by the scaling relation with three stages between seismic moment and source area for inland earthquakes. However, the observed tsunami runup heights along the coast were not reproduced at certain locations, possibly because of the coarse bathymetry data used for the simulation. The 1983 west off Aomori (MJMA 7.1) and the 1964 off Oga Peninsula (MJMA 6.9) earthquakes showed multiple faults near the source area that could be used to reproduce the observed tsunami waveforms; therefore, we could not identify the causative faults. Further analysis using near-field seismic waveforms is required for their identification of their causative faults and their parameters. The scaling relation for inland earthquakes can be used to obtain the slip amounts for offshore active faults in the Sea of Japan and to estimate the coastal tsunami heights and inundation area which can be useful for disaster prevention and mitigation of future earthquakes and tsunamis.Graphical

Validation of tsunami numerical simulation models for an idealized coastal industrial site

ABSTRACT Numerous tsunami numerical models have been proposed, but their prediction accuracies have not been directly compared. For quantifying the modeling uncertainties, the authors statistically analyzed the prediction results submitted by participants in the tsunami blind contest held at the 17th World Conference on Earthquake Engineering. The reproducibility of offshore water level generated due to the tsunami with soliton fission significantly decreased when the nonlinear shallow water equation models (NSWE) was used compared to three-dimensional (3D) models. The inundation depth was reproduced well in 3D models. However, the reproducibility of wave forces acting on the structure and velocities over land was lower in 3D models than that in NSWE models. For cases where the impulsive tsunami wave pressure generated could not be calculated based on the hydrostatic assumption, the prediction accuracy of the NSWE models was higher than that of the 3D models. The prediction accuracies of both models were not improved at small grid-cell sizes. The NSWE model cannot simulate the short-wave component and vertical pressure distribution. Therefore, further developments in 3D models and smoothed particle hydrodynamics methods (SPH) are needed. The presented results contribute to the future development of tsunami numerical simulation tools.

The May 2, 2020, Crete tsunami: comparison between registered and modelled mareograms

The Eastern Mediterranean and Aegean Sea are susceptible to strong earthquakes and tsunami waves. On May 2, 2020 a strong shock with Mw6.6 induced tsunami that was registered in the mareographic network. The tsunami did not cause inundations, but it was the reason to enforce a tsunami alert from the Tsunami Service Providers. Our study is focused on the tsunami numerical simulations of this event and the results are compared to the registered signals in the stations NOA-03 and NOA-04 in Kasos and Ierapetra.

Seiches and the slide/seiche dynamics; subcritical and supercritical subaquous mass flows and their deposits. Examples from Swiss Lakes

Four historically documented large and potentially dangerous lacustrine waves in Swiss lakes show that these waves have been seiches (standing waves) triggered by sublacustrine slides; a statement which is in accordance with the experience of seismologists who see earthquakes triggering seiches in lakes. Nevertheless, large historical waves in Switzerland have recently been modeled as progressive shallow water waves (tsunamis), probably because the slide/seiche dynamics are not known, and experiments with subaquatic slides fail to generate seiches in test–flumes. It appears that these tests exhibit a small shear–energy/slide–energy ratio ε, if compared with the situation in lakes. These facts incite a shear–stress lemma that states that ε is the constituent factor for the slide/seiche coupling. The structure of the subaqueous mass flow deposit (MFD) in lakes Lucerne and Geneva suggests the occurrence of subcritical and of supercritical slide flows. The former would generate a contortite, a MFD with contorted bedding, the latter a debrite (mudclast conglomerate). Potential slide energy considerations are used for an estimation of the amplitudes of large seiches produced by subaquatic slides, a proceeding that yields partly similar and partly very different results, as compared with numerical tsunami simulations.

Regional Probabilistic Tsunami Hazard Analysis for the Mexican Subduction Zone From Stochastic Slip Models

AbstractThe Mexican subduction zone is prone to large earthquakes that impact populated coastal and inland cities due to strong shaking and can generate potentially disastrous tsunamis. Even though the population and infrastructure on the Mexican Pacific coast may experience tsunamis, only sparse instrumentation and scarce tsunami observations exist for both, historical and instrumental, records. This study presents a probabilistic tsunami hazard analysis that can provide information for managing and assessing risks in the region. We use ensembles of numerical tsunami simulations to estimate the probability of exceedance of the maximum tsunami amplitudes, considering the contribution of near sources and slip heterogeneities, for return periods of 100, 500, and 1,000 years. According to 7,946 simulated scenarios, the amplitudes can reach up to 9.5 m along the shoreline. Moreover, tsunami hazard maps, curves, and disaggregation analyses reveal critical hazard points along the coasts of the states of Jalisco, Colima, Michoacán, Guerrero, and Oaxaca.

Probabilistic Tsunami Hazard Assessment in Meso and Macro Tidal Areas. Application to the Cádiz Bay, Spain

Tsunami hazard can be analyzed from both deterministic and probabilistic points of view. The deterministic approach is based on a “credible” worst case tsunami, which is often selected from historical events in the region of study. Within the probabilistic approach (PTHA, Probabilistic Tsunami Hazard Analysis), statistical analysis can be carried out in particular regions where historical records of tsunami heights and runup are available. In areas where these historical records are scarce, synthetic series of events are usually generated using Monte Carlo approaches. Commonly, the sea level variation and the currents forced by the tidal motion are either disregarded or considered and treated as aleatory uncertainties in the numerical models. However, in zones with a macro and meso tidal regime, the effect of the tides on the probability distribution of tsunami hazard can be highly important. In this work, we present a PTHA methodology based on the generation of synthetic seismic catalogs and the incorporation of the sea level variation into a Monte Carlo simulation. We applied this methodology to the Bay of Cádiz area in Spain, a zone that was greatly damaged by the 1755 earthquake and tsunami. We build a database of tsunami numerical simulations for different variables: faults, earthquake magnitudes, epicenter locations and sea levels. From this database we generate a set of scenarios from the synthetic seismic catalogs and tidal conditions based on the probabilistic distribution of the involved variables. These scenarios cover the entire range of possible tsunami events in the synthetic catalog (earthquakes and sea levels). Each tsunami scenario is propagated using the tsunami numerical model C3, from the source region to the target coast (Cádiz Bay). Finally, we map the maximum values for a given probability of the selected variables (tsunami intensity measures) producing a set of thematic hazard maps. 1000 different time series of combined tsunamigenic earthquakes and tidal levels were synthetically generated using the Monte Carlo technique. Each time series had a 10000-year duration. The tsunami characteristics were statistically analyzed to derive different thematic maps for the return periods of 500, 1000, 5000, and 10000 years, including the maximum wave elevation, the maximum current speed, the maximum Froude number, and the maximum total forces.

Tsunami damage estimation in Esmeraldas, Ecuador using fragility functions

<abstract> <p>The current study investigated the probable impact from a tsunami to a populated area located along the northwest ecuadorian coast, specifically in the key oil-industrial city of esmeraldas. a numerical tsunami simulation was performed considering the seismological and tectonic aspects of the area. The damage probability was calculated using fragility functions (ffs). Briefly, 16 cases of source models with slightly different fault parameters were tested, where one was selected as the worst scenario of tsunami inundation. This scenario was a hypothetic earthquake case (mw 8.7) located in front of esmeraldas city, approximately 100 km offshore along the ecuador—colombia trench, with three shallow fault segments (top depth of 10 km), a strike aligned with the trench axis, a middle dip angle of 28°, assuming large slips of 5 to 15 m, and a rake angle of 90°. The results from the numerical simulation were comparable to a similar study previously conducted and with those of historically documented data. The tsunami damage estimation using FFs resulted in estimated damages of 50% and 44% in exposed buildings and population, respectively. Results also showed that the most impacted areas were located next to the coastal shoreline and river. tourism, oil exports, and port activities, in general, would be affected in this scenario; thus, compromising important industries that support the national budget. Results from this study would assist in designing or improving tsunami risk reduction strategies, disaster management, use of coastal zones, and planning better policies.</p> </abstract>

EFFECT OF THE DENSITY OF INUNDATION WATER ON TSUNAMI RUN-UP

Aiming for the advancement of historical and/or prospective tsunami scale evaluations, and focusing on the tsunami run-up, series solutions to the tip position a(t), velocity U (=da/dt) and acceleration d2a/dt2 in the tip region of inundation flow (unsteady flow) with sediment over a uniformly sloping bottom under the condition that the friction factor K is not linked to the density of inundation water, and analytical solutions to a(t), U(t), d2a/dt2, the maximum run-up distance a_m and height Rm under the condition that K is linked to density are derived, and effects of density on them and run-up process are theoretically examined. It is indicated that (1) in the run-up analysis (including numerical simulation) of tsunami with sediment under the condition of a constant K, even if a_m and Rm can be predicted accurately, there is a possibility of evaluating the run-up duration time inaccurately and vice versa, and (2) linking K to density is necessary to solve this matter. An expression for the relationship between K and is also presented. Moreover, it is verified that the derived series and analytical solutions are useful to discuss the effects of density on the run-up of tsunami with sediment through a comparison between the experimental and theoretical maximum run-up distances.

Modeling Maximum Tsunami Heights Using Bayesian Neural Networks

Tsunamis are distinguished from ordinary waves and currents owing to their characteristic longer wavelengths. Although the occurrence frequency of tsunamis is low, it can contribute to the loss of a large number of human lives as well as property damage. To date, tsunami research has concentrated on developing numerical models to predict tsunami heights and run-up heights with improved accuracy because hydraulic experiments are associated with high costs for laboratory installation and maintenance. Recently, artificial intelligence has been developed and has revealed outstanding performance in science and engineering fields. In this study, we estimated the maximum tsunami heights for virtual tsunamis. Tsunami numerical simulation was performed to obtain tsunami height profiles for historical tsunamis and virtual tsunamis. Subsequently, Bayesian neural networks were employed to predict maximum tsunami heights for virtual tsunamis.

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.