Tsunami Research Research Articles

Presenting the Second JDR Award

The Journal of Disaster Research (JDR) has published many special issues in addition to its regular issues. These special issues have included various papers that have covered disasters comprehensively. Among them, the Special Issue on “Tsunami Forces and Effects on Structures” in Vol.4 No.6, 2009 and the Special Issue on “Uncertainties in Tsunami Effects” in Vol.11 No.4, 2016 include practical papers on tsunami disasters which are sure to contribute greatly to tsunami disaster control. The members of the JDR editorial board have unanimously agreed to present this second JDR Award to the editor of the special issues: Harry Yeh Professors, School of Civil and Construction Engineering, Oregon State University, USA I met Professor Harry Yeh for the first time while doing a field survey on the earthquake and tsunami that struck Flores Island, Indonesia in December 1992. He was already a world-renowned researcher, known for his theoretical tsunami research based on accurate hydraulic experiments. I remember that I was deeply impressed with his energetic attitude towards the survey as he worked to reveal phenomena on the disaster site. Since then, I have accompanied him on various disaster surveys, and I have listened to his unique and significant opinions on tsunami studies at many conferences. The two special issues mentioned above reflect his broad range of knowledge and experience. On behalf of the JDR editorial board, I wish to thank Professor Harry Yeh for his efforts and to congratulate him as the winner of the second JDR Award. Tomoyuki Takahashi Professor, Faculty of Societal Safety Sciences, Kansai University, Japan

Multi-proxy evidence for small historical tsunamis leaving little or no sedimentary record

There has been considerable progress in tsunami research in recent years, yet most work has been focussed on identifying and understanding the evidence of large events. This study aimed to identify the evidence of small historical tsunamis in Lyttelton Harbour, New Zealand. The study area has been inundated by multiple relatively small historical tsunamis that left atypical sedimentary evidence (no sand) or no sediment. Shallow trenches revealed discontinuous layers of small grey mud clasts at various depths across the study area, most likely transported from the nearby tidal flats. The origin of these mud clast layers was investigated using a multi-proxy approach comprising sedimentological, geochemical and diatom analyses complemented by dating from 137Cs activity profiles and historical data. Subtle variations consistent with inclusions of marine mud such as a decrease in organic content and magnetic susceptibility and increases in geochemical markers (e.g. Ca/kcps, K/kcps, K/Rb, Si/Rb and Sr/Rb) were found in the sediment profile. Variations in diatom assemblages suggesting a marine influence were also recorded at similar depths, aligning with layers of mud clasts. Using 137Cs activity profiles and historical data, these deposits were attributed to the 1960 Chile Valdivia and 1964 Alaska tsunamis, as well as a possible earlier event. Sedimentary evidence for the 2010 Chile Maule tsunami was not found at the study site, but geochemical analysis of surface samples revealed marked changes in Ca, Cl, Sr and Ti concentrations, indicative of a change from a terrestrial to marine influence. This was used to identify the landward extent of inundation by the 2010 event. Ultimately, this study shows that a broad multi-proxy analysis can distinguish even the subtle signatures of an inconspicuous deposit laid down by a small tsunami.

Tsunami research in Korea

The tsunamis that have occurred in many places around the world over the past decades have taken a heavy toll on human lives and property. The eastern coast of the Korean Peninsula is not safe from tsunamis and has sustained tsunami damage in the past. The aim of this study is to review the past, present, and future of some aspects of tsunami research in Korea. A composite numerical model comprising propagation and inundation models is described. The paper also covers tsunami mitigation efforts in Korea, and a tsunami hazard map is developed and introduced.

A new landslide-induced tsunami simulation model and its application to the 1792 Unzen-Mayuyama landslide-and-tsunami disaster

By combining landslide dynamics research and tsunami research, we present an integrated series of numerical models quantitatively simulating the complete evolution of a landslide-induced tsunami. The integrated model simulating the landslide initiation and motion uses measured landslide dynamic parameters from a high-stress undrained dynamic-loading ring shear apparatus. It provides the numerical data of a landslide mass entering and moving under water to the tsunami simulation model as the trigger of tsunami. The series of landslide and tsunami simulation models were applied to the 1792 Unzen-Mayuyama megaslide and the ensuing tsunami disaster, which is the largest landslide disaster, the largest volcanic disaster, and the largest landslide-induced tsunami disaster to have occurred in Japan. Both the 1792 megaslide and the tsunami portions of the disaster are well documented, making this an excellent test of the reliability and precision of the new simulation model. The simulated tsunami heights at the coasts well match the historical tsunami heights recorded by “Tsunami-Dome-Ishi” (a stone showing the tsunami reaching point) and memorial stone pillars.

Scenario-based assessment of buildings' damage and population exposure due to earthquake-induced tsunamis for the town of Alexandria, Egypt

Abstract. Alexandria is the second biggest city in Egypt with regards to population, is a key economic area in northern Africa and has very important tourist activity. Historical records indicate that it was severely affected by a number of tsunami events. In this work we assess the tsunami hazard by running numerical simulations of tsunami impact in Alexandria through the worst-case credible tsunami scenario analysis (WCTSA). We identify three main seismic sources: the western Hellenic Arc (WHA – reference event AD 365, Mw = 8.5), the eastern Hellenic Arc (EHA – reference event 1303, Mw = 8.0) and the Cyprus Arc (CA – hypothetical scenario earthquake with Mw = 8.0), inferred from the tectonic setting and from historical tsunami catalogues. All numerical simulations are carried out in two sea level conditions (mean sea level and maximum high-tide sea level) by means of the code UBO-TSUFD, developed and maintained by the Tsunami Research Team of the University of Bologna. Relevant tsunami metrics are computed for each scenario and then used to build aggregated fields such as the maximum flood depth and the maximum inundation area. We find that the case that produces the most relevant flooding in Alexandria is the EHA scenario, with wave heights up to 4 m. The aggregate fields are used for a building vulnerability assessment according to a methodology developed in the framework of the EU-FP6 project SCHEMA and further refined in this study, based on the adoption of a suitable building damage matrix and on water inundation depth. It is found that in the districts of El Dekhila and Al Amriyah, to the south-west of the port of Dekhila, over 12 000 (13 400 in the case of maximum high tide) buildings could be affected and hundreds of them could sustain damaging consequences, ranging from critical damage to total collapse. It is also found that in the same districts tsunami inundation covers an area of about 15 km2, resulting in more than 150 000 (165 000 in the case of maximum high tide) residents being exposed.

Tsunami researchers watch for waves from Chile quake

Tsunami researchers watch for waves from Chile quake

An Adequate Dispersive Wave Scheme for Tsunami Simulation

In tsunami research, dispersive wave theory is used to numerically simulate transoceanic and near-field propagation by soliton fission. Many numerical schemes have been proposed to solve the dispersive wave effect, but there has been no reliable criterion for selecting an adequate scheme. To address this, we derive exact numerical stability solutions to the linear finite difference equations of dispersive wave theory by using several numerical methods. Characteristics of the truncation error and the numerical stability of the methods are discussed, and the leap-frog implicit scheme appears to be applicable to practical problems due to its superior stability. A new numerical model that uses an implicit scheme is proposed based on the above results. The dispersive term in the equation of motion is solved by a Poisson-type differential equation and the model can be extended to the nonlinear physics. This model is validated by being compared to the conventional models, and it is applied to a Tonankai-Nankai tsunami as an example of a practical problem. The model shows excellent agreement with both the linear analytical solution and the laboratory experiments. Furthermore, the solutions to this model require less computing time than those of the conventional models.

Building damage from the 2011 Great East Japan tsunami: quantitative assessment of influential factors

Based on the classification provided by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), the damage level of buildings impacted by the 2011 Great East Japan tsunami can be separated into six levels (from minor damage to washed away). The objective of this paper is to identify the significant predictor variables and the direction of their potential relationship to the damage level in order to create a predicting formula for damage level. This study used the detailed data of damaged buildings in Ishinomaki city, Miyagi prefecture, Japan, collected by MLIT. The explanatory variables tested included the inundation depth, number of floors, structural material, and function of the building. Ordinal regression was applied to model the relationship between the ordinal outcome variable (damage level) and the predictors. The findings indicated that inundation depth, structural material, and function of building were significantly associated with the damage level. In addition to this new type of model, this research provides a valuable insight into the relative influence of different factors on building damage and suggestions that may help to revise the classification of current standards. This study can contribute to academic tsunami research by assessing the contribution of different variables to the observed damage using new approaches based on statistical analysis and regression. Moreover, practical applications of these results include understanding of the predominant factors driving tsunami damage to structures, implementation of the relevant variables into the proposed, or alternative model in order to improve current damage predictions by taking into account not only inundation depth, but also variables such as structural material and function of building.

TSUNAMI HAZARD AND BUILDING DAMAGE ASSESSMENT IN THAILAND USING NUMERICAL MODEL AND FRAGILITY CURVES

Assessing the hazard and damage of a potential tsunami is an ongoing challenge in tsunami research. This study begins by simulating tsunami hazards using historical events. A tsunami propagation model is used to obtain the estimated maximum tsunami height along the west coast of Thailand for a rough return period, and rupture locations that have the potential to generate catastrophic tsunamis in Thailand for a specific return period are proposed. A tsunami inundation model is then performed to quantify each building's maximum inundation depth, using high-resolution satellite images to extract each building's location for the areas of interest located in southern Thailand. Nam Khem village and Patong beach are selected as study areas to represent village communities and tourist attractions, respectively. The model results are then used to obtain the numbers of exposed inhabitants and buildings for each earthquake return period. The developed tsunami fragility curves are applied to these figures to determine the number of potentially damaged buildings. The analysis suggests that the propagation model can be used to obtain rough estimations because it provided results similar to those of the inundation model. However, material type must be considered when fragility curves are used in a different country (i.e. reinforced concrete buildings in Thailand from the 2004 tsunami and wooden houses in Japan from the 2011 East Japan tsunami).

The UBO-TSUFD tsunami inundation model: validation and application to a tsunami case study focused on the city of Catania, Italy

Abstract. Nowadays numerical models are a powerful tool in tsunami research since they can be used (i) to reconstruct modern and historical events, (ii) to cast new light on tsunami sources by inverting tsunami data and observations, (iii) to build scenarios in the frame of tsunami mitigation plans, and (iv) to produce forecasts of tsunami impact and inundation in systems of early warning. In parallel with the general recognition of the importance of numerical tsunami simulations, the demand has grown for reliable tsunami codes, validated through tests agreed upon by the tsunami community. This paper presents the tsunami code UBO-TSUFD that has been developed at the University of Bologna, Italy, and that solves the non-linear shallow water (NSW) equations in a Cartesian frame, with inclusion of bottom friction and exclusion of the Coriolis force, by means of a leapfrog (LF) finite-difference scheme on a staggered grid and that accounts for moving boundaries to compute sea inundation and withdrawal at the coast. Results of UBO-TSUFD applied to four classical benchmark problems are shown: two benchmarks are based on analytical solutions, one on a plane wave propagating on a flat channel with a constant slope beach; and one on a laboratory experiment. The code is proven to perform very satisfactorily since it reproduces quite well the benchmark theoretical and experimental data. Further, the code is applied to a realistic tsunami case: a scenario of a tsunami threatening the coasts of eastern Sicily, Italy, is defined and discussed based on the historical tsunami of 11 January 1693, i.e. one of the most severe events in the Italian history.

Near-field tsunami early warning and emergency planning in the Mediterranean Sea

The new European project <em>Near-field Tsunami Early Warning and Emergency Planning in the Mediterranean Sea</em> (NEARTOWARN) faces the need to develop operational tsunami early warning systems in near-field (local) conditions where the travel time of the first tsunami wave is very short, that is less than 30 min, which is a typical case in the North East Atlantic and the Mediterranean Sea region but also elsewhere around the globe. The operational condition that should be fulfilled is that the time of tsunami detection, plus the time of warning transmitting, plus the time of evacuation should not exceed the travel time of the first tsunami wave from its source to the closest evacuation zone. To this goal the time to detect of the causative earthquake should be compressed at the very minimum. In this context the core of the proposed system is a network of seismic early warning devices, which activate and send alert in a few seconds after the generation of a near-field earthquake, when a seismic ground motion exceeding a prescribed threshold is detected. Then civil protection mobilizes to manage the earthquake crisis but also to detect and manage a possible tsunami through a geographical risk management system. For the tsunami detection the system is supported by tide-gauges of radar type, a database of presimulated tsunami scenarios, and a local tsunami decision matrix. The island of Rhodes in the eastern termination of the Hellenic Arc and Trench has been selected for a pilot and operational development of the local tsunami warning system given that the island is a highly popular tourist destination, historically it was hit by large tsunamigenic earthquakes and was recently the master test-site for the pan-European FP6 tsunami research project <em>Tsunami Risk ANd Strategies For the European Region</em> (TRANSFER).

Tsunami Waves of Destruction: The Creation of the “New Australian Catastrophe”

Tsunami Waves of Destruction: The Creation of the “New Australian Catastrophe”

5PM2-A-1 東日本大震災での教訓と津波研究の最前線(招待講演)

The March 11, 2011 Tohoku earthquake tsunami disaster devastated the Pacific coast of northeastern part of Japan. The large number of casualties more than 19,000 and several types of tsunami impact such as inundation in a large area, destructive force destroying houses, buildings, infrastructures, road, and railways, and change of topography due to the erosion and deposition are reported. We have been obtaining results of field surveys as well as numerical simulation and satellite image analysis with ground truth data, to obtain the data of the tsunami and its disaster, and identify extent of tsunami inundation and damage. The fore front of the tsunami research are introduced.

Historical tsunamis and present tsunami hazard in eastern Indonesia and the southern Philippines

Eastern Indonesia and the southern Philippines comprise a huge and seismically highly active region that has received less than the deserved attention in tsunami research compared with the surrounding areas exposed to the major subduction zones. In an effort to redress the balance the tsunami hazard in this region is studied by establishing a tsunami event database which, in combination with seismological and tectonic information from the region, has allowed us to define and justify a number of ‘credible worst‐case’ tsunami scenarios. These scenarios have been used in numerical simulations of tsunami generation and propagation to study maximum water level along potentially affected shorelines. The scenarios have in turn been combined to provide regional tsunami hazard maps. In many cases the simulations indicate that the maximum water level may exceed 10 m locally and even reach above 20 m in the vicinity of the source, which is of the same order as what is forecasted along the Sumatra and Java trenches for comparable return periods. For sections of coastlines close to a source, a tsunami may strike only a few minutes after it is generated, providing little time for warning. Moreover, several of the affected areas are highly populated and are therefore also high risk areas. The combination of high maximum water levels, short warning times, dense populations, and relatively short return periods suggests strongly that the tsunami hazard and risk in these regions are alarmingly high.

Tsunami Risk Management in Pacific Island Countries and Territories (PICTs): Some Issues, Challenges and Ways Forward

The Pacific is well known for producing tsunamis, and events such as the 2011 Tōhoku-oki, Japan disaster demonstrate the vulnerability of coastal communities. We review what is known about the current state of tsunami risk management for Pacific Island countries and territories (PICTs), identify the issues and challenges associated with affecting meaningful tsunami disaster risk reduction (DRR) efforts and outline strategies and possible ways forward. Small island states are scattered across the vast Pacific region and these states have to varying degrees been affected by not only large tsunamis originating in circum-Pacific subduction zones, but also more regionally devastating events. Having outlined and described what is meant by the risk management process, the various problems associated with our current understanding of this process are examined. The poorly understood hazard related to local, regional and distant sources is investigated and the dominant focus on seismic events at the expense of other tsunami source types is noted. We reflect on the challenges of undertaking numerical modelling from generation to inundation and specifically detail the problems as they relate to PICTs. This is followed by an exploration of the challenges associated with mapping exposure and estimating vulnerability in low-lying coastal areas. The latter part of the paper is devoted to exploring what mitigation of the tsunami risk can look like and draw upon good practice cases as exemplars of the actions that can be taken from the local to regional level. Importantly, given the diversity of PICTs, no one approach will suit all places. The paper closes by making a series of recommendations to assist PICTs and the wider tsunami research community in thinking through improvements to their tsunami risk management processes and the research that can underpin these efforts.

DART® Tsunameter Retrospective and Real-Time Data: A Reflection on 10 Years of Processing in Support of Tsunami Research and Operations

In the early 1980s, the United States National Oceanic and Atmospheric Administration Pacific Marine Environmental Laboratory established the fundamentals of the contemporary tsunameter network deployed throughout the world oceans. The decades of technological and scientific advancements that followed led to a robust network that now provides real-time deep-ocean tsunami observations routinely incorporated into operational procedures of tsunami warning centers around the globe. All aspects of the network, from research to operations, to data archive and dissemination, are conducted collaboratively between the National Data Buoy Center, the Pacific Marine Environmental Laboratory, and the National Geophysical Data Center, with oversight by the National Weather Service. The National Data Buoy Center manages and conducts all operational network activities and distributes real-time data to the public. The Pacific Marine Environmental Laboratory provides the research component in support of modeling and network enhancements for improved forecasting capability. The National Geophysical Data Center is responsible for the processing, archiving, and distribution of all retrospective data and integrates DART® tsunameter data with the National Geophysical Data Center global historical tsunami database. The role each agency plays in collecting, processing, and disseminating observations of deep-ocean bottom pressure is presented along with brief descriptions of data processing procedures. Specific examples of challenges and the approaches taken to address these are discussed. National Geophysical Data Center newly developed and available tsunami event web pages are briefly described and demonstrated with processed data for both the Tohoku 11 March 2011 and the Haiti 12 January 2010 tsunami events.

Modelling ecological and other risk factors influencing the outcome of the 2004 tsunami in Sri Lanka

The 2004 Asian tsunami caused widespread devastation across the Indian Ocean. Damage from the waves was influenced by complex interplay of many factors. Using regression models incorporating different impact indicators (occurrence of inundation, inundation distance, and human deaths), we examined factors that significantly influenced tsunami damage in southern Sri Lanka. Land elevation (which is positively correlated with forest presence), sand dunes and coastal convexity (which deflects waves), were protective factors, in terms of whether the tsunami wave inundated within an arbitrary distance of 15 m inland. Water bodies, saltpans and built‐up areas (e.g., roads, development) increased wave inundation distance, while beaches and sand dunes were ameliorative. Built‐up areas also increased death toll. Bathymetry, a proxy for wave height and force, was the only significant factor in all three multivariable models. Coastal areas with a steeper seaward bathymetric slope gradient were less prone to inundation and human fatalities, which is consistent other tsunami research. The presence of coral reefs was highly correlated with bathymetric slope gradient, implying a potentially protective role by coral reefs. Many factors showing greatest protective effect against tsunami damage are geographical features that cannot easily be modified. However, some defence factors identified, such as sand dunes, could potentially be protected. Given the wide‐ranging ecosystem services, unrelated to tsunami protection, ongoing loss/degradation of natural systems including mangroves (not a significant factor in the multivariable models), could be damaging. This might impede certain future coastal development options in post‐tsunami Sri Lanka.

An approximate method of short-term tsunami forecast and the hindcasting of some recent events

Abstract. The paper presents a method for a short-term tsunami forecast based on sea level data from remote sites. This method is based on Green's function for the wave equation possessing the fundamental property of symmetry. This property is well known in acoustics and seismology as the reciprocity principle. Some applications of this principle on tsunami research are considered in the current study. Simple relationships and estimated transfer functions enabled us to simulate tsunami waveforms for any selected oceanic point based only on the source location and sea level data from a remote reference site. The important advantage of this method is that it is irrespective of the actual source mechanism (seismic, submarine landslide or other phenomena). The method was successfully applied to hindcast several recent tsunamis observed in the Northwest Pacific. The locations of the earthquake epicenters and the tsunami records from one of the NOAA DART sites were used as inputs for the modelling, while tsunami observations at other DART sites were used to verify the model. Tsunami waveforms for the 2006, 2007 and 2009 earthquake events near Simushir Island were simulated and found to be in good agreement with the observations. The correlation coefficients between the predicted and observed tsunami waveforms were from 0.50 to 0.85. Thus, the proposed method can be effectively used to simulate tsunami waveforms for the entire ocean and also for both regional and local tsunami warning services, assuming that they have access to the real-time sea level data from DART stations.

Computational Earthquake and Tsunami Research

In this special issues, authors discuss issues in earthquake and tsunami research, as well as in the computational and data infrastructure.

The July 15, 2009 Fiordland, New Zealand Tsunami: Real-Time Assessment

On 15 July 2009, a Mw 7.8 earthquake occurred off the New Zealand coast, which by serendipitous coincidence occurred while the International Tsunami Symposium was in session in Novosibirsk, Russia. The earthquake generated a tsunami that propagated across the Tasman Sea and was detected in New Zealand, Australia and as far away as the US West coast. Small boats close to the epicenter were placed in jeopardy, but no significant damage was observed despite a measured run-up height of 2.3 m in one of the Sounds in close proximity to the source (Wilson in GNS Science Report 46:62 2009). Peak-to-trough tsunami heights of 55 cm were measured at Southport, Tasmania and a height of 1 m was measured in Jackson Bay, New Zealand. The International Tsunami Symposium provided an ideal venue for illustration of the value of immediate real-time assessment and provided an opportunity to further validate the real time forecasting capabilities with the scientific community in attendance. A number of agencies with responsibility for tsunami forecast and/or warning, such as the NOAA Center for Tsunami Research, the Pacific Tsunami Warning Center, GNS Science in New Zealand, the Australian Bureau of Meteorology and the European Commission Joint Research Centre were all represented at the meeting and were able to demonstrate the use of state of the art numerical models to assess the tsunami potential and provide warning as appropriate.