Tsunami Attack Research Articles

Stability of rubble-mound breakwaters under tsunami first impact and overflow based on laboratory experiments

Recent tragic tsunami events, like those that occurred in the Indian Ocean in 2004, and in Japan in 2011, have revealed the need of further work to reduce tsunami risk in coastal areas. An important aspect towards risk reduction is the study of the interaction between tsunami waves and coastal structures as these are the first to receive the tsunami's energy. Dikes and breakwaters must have an adequate structural behavior and maintain some functionality and operability under tsunami attacks to be able to contribute to the reduction of its consequences. Within this scope, laboratory experiments on scaled models of two typical Mediterranean rubble-mound breakwater typologies under tsunami waves were conducted for the first time. The tsunami's action was split into 2 parts: (1) the first impact of solitons was tested by means of large solitary waves and, (2) the subsequent overflow was approached by applying a pump-driven wave maker. The damage on the breakwaters due to these actions was measured and assessed. The result is an in-deep analysis of the relationships among Stability Number, Damage Level and Number of tsunami waves. The outcome of this analysis includes the development of a set of formulae that provide, in the range of the conducted tests, the value of the Damage Parameter, so that tsunami actions can be taken into account in the design of rubble mound structures. Finally, based on the results of these experiments, the threshold values of the Damage Parameter used to characterize damage in armors (Initiation of damage, initiation of destruction, destruction) was particularized for tsunami actions.

Experimental and numerical study on the reduction of tsunami flow using multiple flexible pipes

Oil and gas tanks located in Osaka Bay are highly vulnerable to a tsunami if a Tokai-Nankai-Tonankai earthquake occurs and the consequential tsunami attacks that area. Being inspired by ecologically friendly mangrove and giant-kelps, it has been found that flexible pipes have the capability to reduce wave energy and flow velocity. In this paper, the use of flexible pipes for the reduction of tsunami damage on oil and gas tanks is investigated by means of an experimental and numerical approach. For the experimental study, scaled-model experiments are conducted in the tsunami basin using scaled-model flexible pipes and oil and gas tanks. The tsunami-like wave is generated by the dam break method. Flow velocity in front of and behind the flexible pipes, as well as hydrodynamic forces acting on the model tanks are measured. Experimental results suggested that, from approximately 30 percent to 44 percent of maximum hydrodynamic force could be reduced by the application of flexible pipes. In the numerical approach, 3D CFD simulations are performed for the arrangement of flexible pipes and oil tank, similar to the experimental conditions. A tsunami-like wave is generated by the dam break method and simulation of the flow field is done by solving RANS equations in the open-source CFD toolbox, OpenFOAM. The simulation results show good agreement in terms of flow velocity and hydrodynamic forces acting on the oil tank.

Developing a Web-Based Supporting Application for Individual Evacuation Plans Through Hazard Risk and Geographical Analyses

After the 2011 East Japan Earthquake, the Japanese Cabinet Office has promoted local governments and communities to develop a “Community Disaster Management Plan.” Local governments started to hold workshops to develop the said plan for residents in local communities. However, only a few residents (i.e., those who are interested in disaster prevention) participate in these workshops; thus, most residents do not have opportunities to survey disaster prevention. Considering this issue, we decided to develop a supporting application for individual disaster management plans by analyzing hazard risks and land features. In this research, we focused on evacuation planning for residents. Furthermore, we developed it as web-based application as any resident connected to the internet may be struggling with their evacuation. In our proposed application, users have to take seven steps: (1) learn features of tsunami attack and countermeasures during a tsunami disaster, (2) set start point for evacuation, (3) set first and second goal for evacuation based on lessons learned from the “Miracle of Kamaishi,” (4) search the shortest evacuation route from start point through the first goal to the second goal, (5) review change of elevation on the evacuation route, (6) review hazard risks and land feature on the evacuation route and to reroute if necessary, and (7) download their settled evacuation route to their own devices as a GPX file. After developing a prototype of the application, we published it as a web service. While the publishing was in process, we gathered logs on how users took actions based on our proposed application. Approximately 10 days after publishing the prototype, we analyzed the path of users’ action flow, and we detected issues that need to be resolved to improve esidents’ disaster management capacity during tsunami disasters. Generally, our application helped prepared users for tsunami disaster prevention.

Experimental Study on Hydrodynamic Forces Acting on a Ship Moored alongside a Quay Wall under Tsunami Attack

Experimental Study on Hydrodynamic Forces Acting on a Ship Moored alongside a Quay Wall under Tsunami Attack

Preliminary Study on Dominant Frequency Component of Strong Motion for the Difficult Time for Evacuation in Tsunami Attack Areas during the 2011 Tohoku Earthquake

Preliminary Study on Dominant Frequency Component of Strong Motion for the Difficult Time for Evacuation in Tsunami Attack Areas during the 2011 Tohoku Earthquake

駿河湾における漁協および漁船の津波対策の現状

In this research, as a part of research on maritime traffic analysis for ship evacuation countermeasures at the time of the tsunami attack in Suruga Bay, the current situation of counter measure for earthquake and tsunami at fishery cooperatives are studied. It is appeared that there is no plan to give evacuation orders to ships from the fisherman's cooperative now. The ship owner or the captain has to make a decision in the event of disaster. Also, there are differences in measures against tsunami, and it turned out that there are places that are not provided such as evacuation places. Although the utilization of fishery radio is planed to use at the time of disaster occurrence, it become clear that there are fishery cooperatives that need measures, such as the location of coast stations.

Erratum for “Stability of Breakwater Armor Units against Tsunami Attacks” by Miguel Esteban, Ravindra Jayaratne, Takahito Mikami, Izumi Morikubo, Tomoya Shibayama, Nguyen Danh Thao, Koichiro Ohira, Akira Ohtani, Yusuke Mizuno, Mizuho Kinoshita, and Shunya Matsuba

Erratum for “Stability of Breakwater Armor Units against Tsunami Attacks” by Miguel Esteban, Ravindra Jayaratne, Takahito Mikami, Izumi Morikubo, Tomoya Shibayama, Nguyen Danh Thao, Koichiro Ohira, Akira Ohtani, Yusuke Mizuno, Mizuho Kinoshita, and Shunya Matsuba

河川遡上津波発生時の塩水挙動解析における平面二次元・三次元ハイブリッドモデルの適用

The Nankai Trough Earthquake Tsunami is predicted to occur in the near future in Japan. One of the countermeasures to be taken against the tsunami attack is to predict how long salt water carried by a river-runup tsunami would stay in the river to prevent a water purification plant from taking in salt water. In this study, an application of a hybrid 2DH-3D model to salt water behavior caused by a river-runup tsunami was conducted. The hybrid model is useful for coupling of tsunami propagation from the wave source in 2DH to the flow in the estuary area in 3D, where the density current should be considerable. Two conditions of river flow rate were considered to analyze the effects on the vertically-distributed salinity transport. It was shown that although free surfaces were similar between 2DH and 3D models, significant vertical distributions of the density were present in the 3D region, indicating applicability of the hybrid model to the situation.

Tsunami response system for ports in Korea

Abstract. The tsunamis that have occurred in many places around the world over the past decade have taken a heavy toll on human lives and property. The eastern coast of the Korean Peninsula is not safe from tsunamis, particularly the eastern coastal areas, which have long sustained tsunami damage. The eastern coast had been attacked by 1983 and 1993 tsunami events. The aim of this study was to mitigate the casualties and property damage against unexpected tsunami attacks along the eastern coast of the Korean Peninsula by developing a proper tsunami response system for important ports and harbors with high population densities and high concentrations of key national industries. The system is made based on numerical and physical modelings of 3 historical and 11 virtual tsunamis events, field surveys, and extensive interviews with related people.

Cryptosporidium contamination in surface seawaters in different coastal areas of Thailand: is there any effect from tsunami attack?

*Corresponding author: Sora Yasri, KMT Primary Care Center, Bangkok, Thailand. E-mail: sorayasri@outlook.co.th Dear editor, The Cryptosporidium spp. are important protozoa that can be pathogenic for human beings[1,2]. These protozoa can cause diarrhea and contaminate several foods as well as water. These protozoa can be seen worldwide. In tropical world, they are one of presently problematic pathogenic protozoa. In Thailand, these protozoan still cause diseases and has to be controlled[3]. The contamination of the surface seawater with protozoa is interesting. A recent report showed the high contamination rate in sea mussel which is the common seafood of the Thais[4]. Here, the authors tried to assess the reported prevalence of contamination of Cryptosporidium spp. in sea waters from different coastal areas of Thailand. Of interest, there are 2 previous relating reports on this topic[5,6]. The reported rates of contamination range from 6.0% and 12.7% (Figure 1).

Challenge to Restore the Heritage Buildings Damaged by the 2011 Tsunami Attacks, Kesennuma, Japan

Challenge to Restore the Heritage Buildings Damaged by the 2011 Tsunami Attacks, Kesennuma, Japan

Performance of rubble mound breakwaters under tsunami attack, a case study: Haydarpasa Port, Istanbul, Turkey

Ports are one of the most vulnerable coastal utilities in case of marine natural hazards such as tsunamis and need to be protected against their devastating effects. Thus, studying the effects of tsunamis on protective structures such as breakwaters is critical. The Sea of Marmara is a part of an active earthquake zone that has generated tsunamis in the history. In terms of population density, coastal utilization, and economic potential, Marmara coastline seems most vulnerable to marine hazards. The availability of natural stones allows for wide use of rubble mound breakwaters as coastal protective structures in Turkey. The stability of these types of structures under the attack of storm waves has already been studied. However, their stability and performance under the effect of long waves and tsunami attacks have not yet been studied experimentally. The present study is a case study focusing on Haydarpasa Port, located at the southern entrance of Istanbul Bosphorus Strait (North coast of the Sea of Marmara). It aims to investigate the performance level of the port in case of tsunami attack.Physical model experiments were conducted in the 105-m long wave flume in the Port and Airport Research Institute (PARI), Japan, with a Froude-type length scale of 1/30. The experiments conducted to test the stability of rubble mound breakwater were twofold: (i) solitary wave experiments and (ii) tsunami overflow experiments. The heights of incoming tsunami waves were selected from results of simulations were conducted in the same region (Oyo Int. Co., 2007; Ayca, 2012; Yalciner et al., 2014; Guler et al., 2014; Aytore, 2015). First, the incoming solitary wave heights were selected as 5, 7.5, and 10cm. Using the overflow heights obtained from solitary wave experiments, i.e., wave height at the top of crown wall when the solitary waves are overtopping the crown wall, tsunami overflow experiments were conducted ranging from an overflow height of 1.1cm to 4.6cm. Results of these experiments showed that Haydarpasa Breakwater, especially the crown wall of the breakwater, is not stable under a moderate tsunami attack. Therefore, an improved cross section was also tested under the same conditions, and the improvement proved successful.

Experimental Assessment of Sediment Transport and Bed formation of Sandy Beaches by Tsunami Waves

All experiments in this study were carried out in a flume which was located in the hydraulic laboratory of technical faculty in Guilan University. The wave flume was 12 m long, 0.5 m wide, 0.5 m high and equipped with a wave-producing system and ultrasonic sensors. The objectives of current experimental study are to investigate sediment transport, bed formation and sustainability of sandy beaches with different grain size under tsunami attack. Sediment transport, caused by tsunamis, brings about severe damages to human beings, structures, beach topography and environment. Due to the devastating, destructive and scouring effect of tsunami waves, assessing their operation is of great importance. Experimental studies can be significantly helpful to evaluate the process of transported sediment by a tsunami. Three traps were employed to examine sediment transport in different parts of the beach. The achieved results indicated that wave breaking point has significant effect on the beach profile deformation and sustainability. Furthermore, grains with varying sizes, in the same conditions behave differently. As a result, for finer grains wave backwash has more effects on the sediment transport, while for coarser grains the wave itself has a main role in sediment transport.

Assessment of tsunami hazards in ports and their impact on marine vessels derived from tsunami models and the observed damage data

This paper presents a detailed study of tsunami hazard in ports and its correlation with the damage suffered by marine vessels. The study aims to develop a new loss function to estimate the potential damage of marine vessels due to tsunami attack based on a novel multivariate statistical modeling method, which used several explanatory variables simultaneously to estimate an outcome or the probability of such outcome. In the first part of the paper, tsunami heights and velocities are numerically modeled by using high-resolution bathymetry and topography data for the southern part of Honshu Island. We apply statistical methods to the complete sequence of spatially distributed time series of tsunami parameters in order to obtain the best fit with the observed damage data. In the second part, we develop loss functions for marine vessels by using ordinal regression, which uses simultaneously several explanatory variables. We perform several statistical tests to determine the appropriate model variables to be used in developing three-dimensional loss estimation surfaces, which provide probability of loss for each combination of measured or simulated values of tsunami parameters. The main feature of the developed loss functions presented in this study is their capability to integrate the key factors influencing the damage probability, such as tsunami parameters, characteristics of marine vessels and the impact of collision experienced by the vessels during the tsunami. Such a robust method, therefore, is crucially important to understand the tsunami impact on ports and, particularly on marine vessels.

Consideration for effective height of sea walls against tsunami

Tsunami wave height data at several sites in Tohoku district in Japan were examined and an empirical extreme value distribution with both upper and lower bounds was applied to model the cumulative probability distribution function of annual maximum wave height. Then by estimating the construction cost of sea walls against the tsunami and the expected damage cost due to a tsunami attack, the expected total cost was studied. Observation of the tendency of expected total cost with the design height of a sea wall indicates that sea wall construction is not economically justified, unless the height exceeds the upper bound of tsunami wave height.

ANALYSIS OF TSUNAMI BEHAVIOR AND THE EFFECT OF COASTAL FOREST IN REDUCING TSUNAMI FORCE AROUND THE COASTAL DIKES

Many coastal dikes in Iwate, Miyagi and Fukushima prefectures in Japan were damaged due to the 2011 Great Eastern Japan Earthquake Tsunami. The primary failure mode of these dikes was scour failure at the leeward toe by the overflowing tsunami. However, the forces exerted by the tsunami wave against the dikes were reduced to the presence of some obstacles (such as trees) located behind the dikes, increasing the tsunami inundation height immediately behind the structure and actually helping to reduce the force on the dike itself. In order to analyze how tsunamis affected coastal dikes, the authors carried out post-tsunami field surveys and laboratory tests using dikes and different coastal forest models. The critical failure mechanism of dikes was analyzed and co-related to tsunami overflowing pattern. In addition, the experimental results show how coastal forest can help to reduce the damage caused by the tsunami to coastal dikes by increasing water depth and changing the tsunami motion pattern. Thus, the placement of coastal forests behind dikes can help to increase their resilience against tsunami attack, and should be considered as part of a disaster management strategy for certain tsunami prone areas.

Lessons for countermeasures using earth structures against tsunami obtained in the 2011 Off the Pacific Coast of Tohoku Earthquake

Since many infrastructures, such as sea walls, sand beaches, forests, etc., were severely damaged or destroyed by the tsunami that occurred due to the 2011 Off the Pacific Coast of Tohoku Earthquake, it is said that the resistant functions of the above structures against tsunami attacks did not perform well. However, some structures are known to have resisted the tsunami, based on field surveys conducted after the earthquake by the authors and others; and thus, the resistant functions of those infrastructures against tsunami should be estimated more properly. This paper focuses on earth structures, including river levees and road embankments, both damaged and undamaged, at 13 sites in Miyagi Prefecture, Chiba Prefecture, and Ibaraki Prefecture. They have been investigated through field surveys and other related data, such as satellite photographs taken before and/or after the tsunami. Furthermore, 10 dug pools, eroded by the flood stream on the back side of sea walls and banks during the tsunami, are also investigated to clarify their effects against tsunami attacks for use as future hardware countermeasures. Based on the above field investigations, several important lessons on hardware countermeasures against tsunami, using earth structures, are discussed. And, performance-based design concepts for reconstruction after this earthquake and for the reduction of future tsunami damage are discussed and proposed.

Beach profile change at Hasaki, Japan, caused by 5-m-high tsunami due to the 2011 off the Pacific coast of Tohoku Earthquake

Abstract The beach profile change caused by the 5-m-high tsunami striking the sandy Hasaki coast of Japan in 2011 was investigated using numerical simulation results and a detailed field data set including the beach profiles measured just 6 h before and three days after the tsunami attack. The magnitude of the tsunami-induced profile change had roughly the same relation to the wave energy flux as did the profile changes caused by wind-generated waves at this location. However, the mechanisms underlying the morphological changes were different. The beach profile changes due to wind waves were induced by smaller bottom stresses with longer duration, whereas the profile change due to the tsunami was induced by larger bottom stresses with shorter duration. Simulation results showed that the tsunami-induced beach profile change, including the offshore bar erosion, was largely caused by suspended sediments transported by the uprush flows of the first two tsunami waves. Compared with the amount of beach profile change at Banda Aceh due to the 2004 Indian Ocean tsunami, that at Hasaki due to the 2011 tsunami was small. The main reason for this is likely the difference in tsunami height: 5 m at Hasaki and 10 m at Banda Aceh. The second cause may be the topography of the land.

Fire and explosion disasters occurred due to the Great East Japan Earthquake (March 11, 2011)

The Great East Japan Earthquake (magnitude 9.0 Mw: the moment magnitude scale, based on the seismic moment of the earthquake) occurred at 14:46, March 11, 2011. It triggered huge tsunami waves (seismic sea waves) that reached heights of up to about 20 m. In this paper, the fire and explosion disasters occurred due to the Great East Japan Earthquake are reported shortly. Some fires occurred in seacoast areas after tsunami attacks and some of them were spreading very widely to the tsunami flooded areas. It is important to study the mechanisms of such fires (tsunami fires) for preparing huge tsunami. After the earthquake, a very severe accident happened in the Fukushima Daiichi nuclear power plant. Three reactors experienced full meltdown. During this disaster, hydrogen explosions occurred and made the situation more serious. It has to be realized once again that the countermeasures for hydrogen explosions is indispensable. Also Large scale BLEVEs (Boiling Liquid Expanding Vapor Explosions) happened at LPG storage area in an oil refinery in Chiba Prefecture. This accident started from the falling down of an LPG storage tank by earthquake motions. The tank was heavier than usual, as it was filled with water (1.7 times heavier than LPG) for periodic inspection. Considering these disasters, we have to think about how we prepare the accident of low probability and of very severe consequence. Recently, the risk based approach is widely utilized. However, for such disasters it seems not enough to perform safety management only by risk based approach. Not only probabilistic approach (Risk), but also deterministic approach (Emergency plan, Mitigation technique) should be taken in account.

L-모멘트법을 이용한 지진해일고 분포형 결정

최근 파괴적이고 예상하기 힘든 지진해일이 발생하고 있고 이에 따라 지진해일 방재대책의 필요성이 급격히 증가하고 있다. 본 연구에서는 수치모의를 통한 방법과 통계적인 방법을 결합하여 지진해일의 파고를 예측하고 최적분포형의 도출 방법을 제시하였다. 수치모의를 통해 지점별 최대해일고를 추출하였고, 이 해일고를 표본으로 L-모멘트법을 적용하였다. L-모멘트를 통해 산출된 통계치를 L-모멘트 비 다이어그램에 적용하여 동해안에 대한 최적 분포형을 산정하였다. 동해안 전역에 대한 지진해일 분포형은 주로 Generalized Pareto 분포임을 확인했다. Recently, the necessity for mitigation against devastating and unexpected tsunami attacks is significantly increasing. In this study, a combination of numerical and statistical techniques was used to estimate tsunami heights and investigate a best-fit distribution. By using a numerical simulation, tsunami heights were obtained along the Eastern Coast of the Korean Peninsula and they were used for applying L-moment method as the sample data. The best-fit distributions were determined by an L-moment ratio diagram. The distribution of tsunami heights along the Eastern Coast of the Korean Peninsula was mainly represented by the generalized Pareto distribution.