Historical Tsunami Research Articles

Prediction of Tsunami Waves by Uniform Slip Models

AbstractConventional tsunami warning systems for local and far‐field areas utilize uniform slip models to predict tsunami waves. The reasons are twofold. First, it is challenging to develop accurate finite‐fault slip models in a short time after an earthquake. Second, tsunami waves are long waves, and hence, the main feature may be predicted without knowing earthquake rupture details. Still, there have been few studies that quantitatively analyze the errors caused by uniform slip models. In this paper, we evaluate if and how such models may be applied for tsunami warnings. For the 2011 Tohoku, 2014 Iquique, and 2015 Illapel tsunamis, we first construct optimum uniform slip models with minimum tsunami waveform misfit and then compare the synthetic tsunami waves with finite‐fault model predictions. Predictions from both type of models match the tsunami data very well, indicating that the prediction errors caused by neglecting slip heterogeneity are insignificant. Further, we derive a common relation between the rupture area and earthquake magnitude. Additionally, the optimum rupture length and width ratio in terms of predicting tsunami waves is determined to be 1 for the three earthquakes. Lastly, we find that moving the uniform slip model to the center of global Centroid Moment Tensor solution produces reasonably small errors in the predicted waveforms. Applying the methodology to three more historic tsunamis shows that uniform slip models can well recover the Deep‐ocean Assessment and Reporting of Tsunamis system recordings, but the rupture center can differ from the global Centroid Moment Tensor solution. Our findings can potentially prompt more reliable tsunami warning strategies for future events.

Vulnerability Characteristics of Tsunamis in Indonesia: Analysis of the Global Centre for Disaster Statistics Database

Regional disaster data are important for understanding the characteristics of disasters and for identifying potential mitigation measures. However, many countries have no official disaster database that includes information such as numbers of deaths or damaged buildings for each disaster event. The Global Centre for Disaster Statistics (GCDS) was established to assist countries and organizations in the collection of disaster data. At present, a significant amount of tsunami disaster data are available from Indonesia, which will be used to demonstrate its application for analyzing vulnerability characteristics of historical tsunamis. There are 53 data points covering 13 tsunami events between the year 1861 and 2014. Based on data availability, five tsunami events, namely the 1977 Sumba, the 2004 Indian Ocean, the 2006 Java, the 2010 Mentawai, and the 2011 Great East Japan, were selected. Numbers of deaths and damaged buildings were used in combination with hazard data to estimate vulnerability, defined as the ratio between maximum flow depth against death and building damage ratios. Numbers of evacuees were initially used to estimate actual numbers of exposed population but it was later discovered that this parameter overestimated the exposed population in certain cases. As a result, this study presents the vulnerability characteristics of people and buildings in Indonesia, exposed to unusual or extreme tsunamis, mostly in a condition without or with limited access to official warnings. In brief, a maximum flow depth of 5 m caused an approximate 100% death ratio in the majority of Indonesian tsunamis in this study. On the other hand, death ratio in the 2011 Japan tsunami was limited to 10% because of the early warning and high disaster awareness. Effective disaster risk reduction activities such as official warnings, evacuations, and tsunami education were observed for certain locations. Lastly, adding hazard and population data at the village level is recommended for improving the collection of future tsunami disaster data for the GCDS database.

Stratigraphic evidence of historical and prehistoric tsunamis on the Pacific coast of central Japan: Implications for the variable recurrence of tsunamis in the Nankai Trough

To complement historical written records of tsunamis in the Nankai Trough and reconstruct prehistoric tsunami records, we conducted a coring survey at a coastal lowland in Mie Prefecture, central Japan. We found 10 sand layers deposited from about 4500 to 500 years ago. The layers are interpreted as tsunami deposits because of the presence of abundant bioclasts of marine organisms and sedimentary structures such as alternating sub-layers of sand and silt, rip-up clasts, and upward-fining structures, all of which are common in modern tsunami deposits. At the study site, no substantial seawater inundations and sand depositions have been recorded even for the largest typhoons to ever hit the region. There are historical accounts of earthquake and tsunami damage along the Nankai Trough in 1498, 1361, 1096, 887, and 684 CE. Estimated ages of the youngest three sand layers overlap well with tsunamis in 1498, 1096, and 684 CE. Our results support the hypothesis suggested by archaeological studies that the 684 CE rupture extended farther eastward than the historical record indicates or that another tsunami occurred at some time close to 684 CE. We did not find any sand layers that were definitely correlated with the tsunamis of 1361 and 887 CE, which are thought to have occurred by multi-segment ruptures of the Nankai Trough that includes the segment directly offshore from the study site. If the sand layers found at the study site were deposited by the tsunamis of 1498, 1096, and 684 CE, and if the tsunamis of 1361 and 887 CE did not inundate the study site, the tsunami recurrence interval during the relevant time period was about 400 years. This finding does not support the widely believed hypothesis that earthquakes and tsunamis occur at regular intervals of approximately 100 years in this area. In addition, similar to the historical tsunamis, intervals of geologically recorded prehistoric tsunamis at the study site vary from about 100 to 600 years. The hypothesis of variable recurrence of earthquakes and tsunamis along the Nankai Trough should be tested by future geological and historical studies in unbiased way.

Numerical experiments on effect of river mouth morphology on tsunami behavior in rivers

ABSTRACT In the 2011 Tohoku Earthquake Tsunami, run-up of the tsunami along rivers expanded the damaged area into more inland areas far from the coast. High water level in rivers was kept for more than several times of the wave period in the 2011 event, while more simple periodical oscillations of the water level superposed on the tidal motion was observed in the 2010 Chile Tsunami event. The difference of behaviors of tsunami in rivers was discussed with related to the magnitude of tsunami and river mouth morphology through two numerical experiments in this paper. In the first numerical experiments, the run-up of historical tsunamis was simulated along Kitakami River. It was found that the discharge of tsunami flow across the river mouth was proportional to third power of water depth if overflow of the sand spit occurred, and that caused unbalance of water volume coming into and going out from the river channel. Through the second numerical experiment with simple model bathymetry and sinusoidal waves, it was found that discharge during both tsunami run-up and run-down across river mouths is reduced by sand spits at the river mouths and the reduction effect is more significant during flow rushing into the rivers than that during return flow.

Debris impact under extreme hydrodynamic conditions part 2: Impact force responses for non-rigid debris collisions

Historical tsunami events have resulted in extreme damage to coastal regions worldwide. Among the various loads associated with tsunami waves, debris impact has been shown to cause major damage to nearshore infrastructure. As a result, debris impact loads have been included prominently in existing design guidelines and standards, such as the FEMA P-646 [11] and ASCE7 Chapter 6 [6]. In the present study, single debris impacts on structures was experimentally investigated under tsunami-like wave conditions. Eccentric and oblique impacts of a model shipping container (length scale 1:40) on a non-rigid structure were examined. The experimental results of the non-rigid impacts are discussed in the context of the existing force equations which were derived under the assumption of rigid-body impact theory. As expected, the elasticity of the structure was determined to influence and, specifically, reduce the magnitude of the debris impact forces. Existing impact force equations are herein critically discussed through comparison with the experimental results and, finally, modifications to existing force equations to account for non-rigid collisions are proposed.

Potential tsunami risk assessment to the city of Alexandria, Egypt.

Tsunami extreme events present a highly significant hazard and considerable risk to the coastal communities. The continued occurrence of tsunami incidents, together with population growth, increases the risk in coastal communities. Two known catastrophic historic tsunamis in Alexandria occurred in the years 365 and 1303AD, with reported wave heights of 1m and 2.9m, respectively. Approximately 5000 people lost their lives and 50,000 homes were destroyed in the city after the earthquake in 365. The 1303 tsunami destroyed the great lighthouse of Alexandria, one of the seven wonders of the ancient world. In order to avoid such events in the future, a detailed knowledge about the tsunami phenomenon and its potential risk is needed. In this paper, the vulnerability and risk to the city of Alexandria will be examined by remote sensing and GIS techniques considering three scenarios. Methodology used depends on building a comprehensive GIS in addition to recent satellite images. After digitizing raster data, it was then stored into a vector format. A digital parcel map was created; attributes (like distance to shore line, elevation, land use/cover, and population) for each polygon were added. Using the Shuttle Radar Topography Mission images, a digital elevation model was created, to test all the tsunami scenarios (based on 5m, 9m, and 20m wave's height). Finally, vulnerability analysis including physical as well as social and economic constraints was executed for the determination of the vulnerability level of elements. Results indicated that Alexandria city is highly vulnerable to tsunami hazard. Very high risk covers the biggest portion of the area in Alexandria (49.16% and 58.71%), followed by high risk (30% and 28.41%), medium risk (13.61% and 7.76%), and low and very low risk (20.82% and 12.88%).

Generation of a New Tsunami Hazard Map for the Port of Imwon

Lee, S.-O.; Kim, W.-J., and Cho, Y.-S., 2018. Generation of a New Tsunami Hazard Map for the Port of Imwon. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 726–730. Coconut Creek (Florida), ISSN 0749-0208.Tsunamis, which are long-period oceanic waves mainly generated by undersea earthquakes, can be one of the most devastating types of natural hazard. Tsunamis frequently occur around the rim of the Pacific Ocean, including the East Sea. The most plausible and frequently chosen tsunami hazard mitigation measure is to generate a tsunami hazard map based on probable maximum tsunamis. Probable maximum tsunamis in the present study are three historical tsunamis and 11 virtual tsunamis. The port of Imwon, located on the eastern coast of the Korean Peninsula, is vulnerable to an unexpected tsunami strike. The Central East Sea Tsunami that struck in May 1983 resulted in three human casualties (one death and two people missing and presumed dead) and property damage. The present study generates a tsunami hazard map for the port of Imwon. Shelters and evacuation routes are determined according to selection criteria and a field survey. The newly developed tsunami hazard map can be used by local authorities in the case of a real tsunami.

Tsunami deposits and hazard along north coast of Egypt correlate with historical earthquake records of eastern Mediterranean

AbstractPaleotsunami deposits and tsunami scenarios are investigated along the north coast of Egypt in the framework of the National Research Institute of Geophysics and Astronomy (NRIAG) and EC-Funded ASTARTE European tsunami and the French-Egyptian IMHOTEP projects. The study area located west of Alexandria is selected according to historical earthquakes and related inundation events as recorded in the archives. The two selected sites at Kefr Saber ∼32-km west of Marsa Matruh city and ∼10 km northwest of the El Alamein village are inner Laguna protected by 2 to 20-m-high dunes parallel to the shoreline. The two selected sites were chosen according to geomorphological and geological aspects. Five trenches and 12 cores were dug in two selected sites Kefr Saber and EL Alamein. X-ray scanning, magnetic susceptibility, grain size analysis, sampling and macrofossil detections, XRD analysis, total organic and inorganic matter measurements and carbon dating were carried out to identify the paleotsunami signatures. The high energy white sandy layer with rich in reworked fossils at Kafr Saber are correlated with 21 July 365 in Kafr Saber, while the four characteristic high energy sedimentary layers at the El Alamein site are correlated with the historical tsunami events of 1600 BC, 21 July 365, 8 August 1303, 24 June 1870.

Historical Tsunami Records on Russian Island, the Sea of Japan

In this article, we provide data evidencing tsunamis on Russian Island over the last 700 years. Reconstructions are developed based on the analyses of peat bog sections on the coast of Spokoynaya Bay, including layers of tsunami sands. Ancient beach sands under peat were deposited during the final phase of transgression of the Medieval Warm Period. We used data on diatoms and benthic foraminifers to identify the marine origin of the sands. The grain size compositions of the tsunami deposits were used to determine the sources of material carried by the tsunamis. The chronology of historical tsunamis was determined based on the radiocarbon dating of the underlying organic deposits. There was a stated difference between the deposition environments during tsunamis and large storms during the Goni (2015) and Lionrock (2016) typhoons. Tsunami deposits from 1983 and 1993 were found in the upper part of the sections. The inundation of the 1993 tsunami did not exceed 20 m or a height of 0.5 m a.m.s.l. (0.3 above high tide). The more intensive tsunami of 1983 had a run-up of 0.65 m a.m.s.l. and penetrated inland from the shoreline up to 40 m. Sand layer of tsunami 1940 extend in land up to ~ 50 m from the present shoreline. Evidence of six tsunamis was elicited from the peat bog sections, the deposits of which are located 60 m from the modern coastal line. The deposits of strong historic tsunamis in the Japan Sea region in 1833, 1741, 1614 (or 1644), 1448, the XIV–XV century and 1341 were also identified on Russian Island. Their run-ups and inundation distances were also determined. The strong historic tsunamis appeared to be more intensive than those of the XX century, and considering the sea level drop during the Little Ice Age, the inundation distances were as large as 250 m.

Correlation Equation of Fault Size, Moment Magnitude, and Height of Tsunami Case Study: Historical Tsunami Database in Sulawesi

Sulawesi, one of the biggest island in Indonesia, located on the convergence of two macro plate that is Eurasia and Pacific. NOAA and Novosibirsk Tsunami Laboratory show more than 20 tsunami data recorded in Sulawesi since 1820. Based on this data, determination of correlation between tsunami and earthquake parameter need to be done to proved all event in the past. Complete data of magnitudes, fault sizes and tsunami heights on this study sourced from NOAA and Novosibirsk Tsunami database, completed with Pacific Tsunami Warning Center (PTWC) catalog. This study aims to find correlation between moment magnitude, fault size and tsunami height by simple regression. The step of this research are data collecting, processing, and regression analysis. Result shows moment magnitude, fault size and tsunami heights strongly correlated. This analysis is enough to proved the accuracy of historical tsunami database in Sulawesi on NOAA, Novosibirsk Tsunami Laboratory and PTWC.

Assessment of the tsunami hazard on the Russian coast based on a new catalogue of tsunamis in the Black Sea and the Sea of Azov

We present the results of work on the compilation of a fuller and more comprehensive historical catalogue of earthquakes and tsunamis in the basin of the Black Sea and the Sea of Azov, an area of primary importance for the Russian Federation. In the 20th century, there were no significant tsunamis in the Black Sea; therefore, its coast was not considered tsunami-prone. A systematic search for new data sources, a revision of earlier ones, and the use of new approaches to the identification of tsunamigenic events resulted in a more than doubling of the number of known tsunamigenic events in this basin, bringing it up to 50. The total length of the new tsunami catalogue reached 3000 years, which makes it the second longest after the Mediterranean tsunami catalogue (about 4000 years). Taking into account the seismotectonic features of the Black Sea region, we processed data on historical tsunamis and analyzed the geographical and temporal distributions of their sources. For all tsunamigenic events we performed a parameterization of available information about their sources and coastal manifestations, evaluated the tsunami intensity based on the Soloviev-Imamura scale, and proposed a classification of tsunami and tsunami-like water wave disturbances based on their genesis. Tsunami run-up heights, inland penetration, and damage were estimated with regard for the newly found data. Among the identified historical events, there are devastating tsunamis with run-ups of 4-5 m, sometimes up to 6-8 m, which resulted in disastrous consequences for several ancient cities (Dioscuria, Sebastopolis, Bizone, and Panticapaeum) and many coastal settlements. Expert assessments of the most tsunami-prone areas of the coasts are given.

Reprint of 'Unusual geologic evidence of coeval seismic shaking and tsunamis shows variability in earthquake size and recurrence in the area of the giant 1960 Chile earthquake'

An uncommon coastal sedimentary record combines evidence for seismic shaking and coincident tsunami inundation since AD 1000 in the region of the largest earthquake recorded instrumentally: the giant 1960 southern Chile earthquake (Mw 9.5). The record reveals significant variability in the size and recurrence of megathrust earthquakes and ensuing tsunamis along this part of the Nazca-South American plate boundary. A 500-m long coastal outcrop on Isla Chiloé, midway along the 1960 rupture, provides continuous exposure of soil horizons buried locally by debris-flow diamicts and extensively by tsunami sand sheets. The diamicts flattened plants that yield geologically precise ages to correlate with well-dated evidence elsewhere. The 1960 event was preceded by three earthquakes that probably resembled it in their effects, in AD 898–1128, 1300–1398 and 1575, and by five relatively smaller intervening earthquakes. Earthquakes and tsunamis recurred exceptionally often between AD 1300 and 1575. Their average recurrence interval of 85years only slightly exceeds the time already elapsed since 1960. This inference is of serious concern because no earthquake has been anticipated in the region so soon after the 1960 event, and current plate locking suggests that some segments of the boundary are already capable of producing large earthquakes. This long-term earthquake and tsunami history of one of the world's most seismically active subduction zones provides an example of variable rupture mode, in which earthquake size and recurrence interval vary from one earthquake to the next.

The 1997 Kronotsky earthquake and tsunami and their predecessors, Kamchatka, Russia

Abstract. The northern part of the Kamchatka subduction zone (KSZ) experienced three tsunamigenic earthquakes in the 20th century – February 1923, April 1923, December 1997 – events that help us better understand the behavior of this segment. A particular focus of this study is the nature and location of the 5 December 1997 Kronotsky rupture (Mw ∼ 7.8) as elucidated by tsunami runup north of Kronotsky Peninsula in southern to central Kamchatsky Bay. Some studies have characterized the subduction zone off Kronotsky Peninsula as either more locked or more smoothly slipping than surrounding areas and have placed the 1997 rupture south of this promontory. However, 1997 tsunami runup north of the peninsula, as evidenced by our mapping of tsunami deposits, requires the rupture to extend farther north. Previously reported runup (1997 tsunami) on Kronotsky Peninsula was no more than 2–3 m, but our studies indicate tsunami heights for at least 50 km north of Kronotsky Peninsula in Kamchatsky Bay, ranging from 3.4 to 9.5 m (average 6.1 m), exceeding beach ridge heights of 5.3 to 8.3 m (average 7.1 m). For the two 1923 tsunamis, we cannot distinguish among their deposits in southern to central Kamchatsky Bay, but the deposits are more extensive than the 1997 deposit. A reevaluation of the April 1923 historical tsunami suggests that its moment magnitude could be revised upward, and that the 1997 earthquake filled a gap between the two 1923 earthquake ruptures. Characterizing these historical earthquakes and tsunamis in turn contributes to interpreting the prehistoric record, which is necessary to evaluate recurrence intervals for such events. Deeper in time, the prehistoric record back to ∼ AD 300 in southern to central Kamchatsky Bay indicates that during this interval, there were no local events significantly larger than those of the 20th century. Together, the historic and prehistoric tsunami record suggests a more northerly location of the 1997 rupture compared to most other analyses, a revision of the size of the April 1923 earthquake, and agreement with previous work suggesting the northern KSZ ruptures in smaller sections than the southern KSZ. The final suggestion should be considered with caution, however, as we continue to learn that our historic and even prehistoric records of earthquakes and tsunamis are limited, in particular as applied to hazard analysis. This study is a contribution to our continued efforts to understand tectonic behavior around the northern Pacific and in subduction zones, in general.

Learning from a Disaster: Improving Nuclear Safety and Security after Fukushima ed. by Edward D. Blandford, Scott D. Sagan

Reviewed by: Learning from a Disaster: Improving Nuclear Safety and Security after Fukushima ed. by Edward D. Blandford, Scott D. Sagan Takuji Okamoto (bio) Learning from a Disaster: Improving Nuclear Safety and Security after Fukushima. Edited by Edward D. Blandford and Scott D. Sagan. Palo Alto: Stanford University Press, 2016. Pp. 232. $27.95. Except one environmental historian, the contributors to this collection of articles are social scientists and engineers, and all chapters, including the one by the only historian, mainly analyze contemporary factors that caused and probably worsened the disaster in the Fukushima Daiichi nuclear plant in March 2011. Historians, nevertheless, will find the topics discussed here relevant to their interests. Those who regard the unprecedented tsunami as the cause of the Fukushima nuclear failure might think that it could not have been prevented anyway. They might even accept the inadequate seawall heights of the nuclear plant as the result of reasonable statistical risk analysis concerning the historical tsunamis. However, after seeing Nobumasa Akiyama (Chapter 4) argue that poor crisis leadership in the government and the power company [End Page 192] prevented appropriate decision-making right after the earthquake and tsunami, one might start wondering whether the disaster could not have been handled in a somewhat better manner, though stopping it from developing at all might seem inconceivable. It might not have been so bad as it actually was. Toshihiro Higuchi (Chapter 5) criticizes the Tokyo government’s over-reliance on numerical standards for radiation protection that confused and troubled the evacuating population. Both Kaoru Naito (Chapter 3) and Kazuto Suzuki (Chapter 6) point to the possible effectiveness of the synergy between nuclear security and safety efforts, represented by the so-called B.5.b measures developed after 9/11 in the United States, which were somehow not adopted by the Japanese. Phillip Y. Lipsy, Kenji E. Kushida, and Trevor Incerti (Chapter 7) conclude that in Japan, the largest power companies’ nuclear plants were more vulnerable to tsunami and flooding than those of the smaller businesses, implicitly blaming the power industry’s regional monopoly system. Furthermore, Edward D. Blandford and Michael M. May (Chapter 8) summarize that in addition to being part of the background of the failure, “lack of transparency before the accident made the political consequences of the accident more severe than they might otherwise had been” (p. 195). And finally, according to Gregory D. Wyss (Chapter 2), even the siting and design of the Fukushima Daiichi and its inadequate seawall heights were the results of the Design Basis philosophy that the Japanese government and nuclear industry had been invoking. With a different Design Basis philosophy, the flooding could have been prevented on 11 March 2011, as was observed at the Onagawa plant, which underwent a tsunami as high as the one that struck Fukushima Daiichi (Kushida, Chapter 1). After these examinations of the factors that caused and worsened the disaster, the authors naturally look to the future and suggest ways to improve worldwide nuclear safety and security. The social scientists’ and engineers’ analyses of the Fukushima disaster will give historians precious insight on where they should seek its historical root causes. Besides topics that have been discussed well since the Fukushima nuclear failure, some other issues still remain untouched. They include, for example, apparent disregard of security matters in the nuclear industry, lack of concern with crisis management in the government, and historical development of the use of Design Basis. Though these may no longer seem to be closely related to the interests in the Fukushima disaster, they can open up new possibilities for historical study of technology in general, which would not have been very obvious to historians but for such contemporary analyses as this book presents. [End Page 193] Takuji Okamoto Takuji Okamoto is professor of history of science at the University of Tokyo. His interest is in the history of physics in the United States, the development of operationalism of P. W. Bridgman, and the cultural and political implications of science and technology in modern Japan. Copyright © 2018 Society for the History of Technology

Applying the perceived probability of risk and bias toward optimism: Implications for travel decisions in the face of natural disasters

Unperceived risk leads to lack of preparedness. This study aims to examine tourists' risk perception and travel decisions using as variables demographics, knowledge about safety, and country of residence. Samples were gathered in Thailand, Japan, Australia, and Indonesia. A total of 916 completed questionnaires of five replicated surveys were used in this study. More than halve of the respondents whose country had been affected by the Indian Ocean tsunami in 2004 did not perceive tsunami risk when 10 years has passed. Frequency of tsunami occurrence was positively related to perceived tsunami probability. This study confirms the theory of probability that low frequency of a natural disaster results in unperceived risks. Even if their destination had a history of tsunamis, tourists' perceived risk of another such occurrence happening during their visit is low (that is, the risk of natural disaster is low). While the literature in earth science found that residents of risky areas tend to be optimistic about the place where they live, our study extends the theory of optimistic bias to indicate that the same optimistic bias is applicable to tourists. Asia and Southeast Asia were perceived as tsunami-prone but tourists still travelled there. Our study found that tourist risk perception was related to frequency of tsunami occurrence and was destination specific. The perception of probability of a natural disaster is also related to proximity and past experience. Replications are necessary to validate results before generalization.

The Numerical Technique for the Landslide Tsunami Simulations Based on Navier–Stokes Equations

The paper presents an integral technique simulating all phases of a landslide-driven tsunami. The technique is based on the numerical solution of the system of Navier–Stokes equations for multiphase flows. The numerical algorithm uses a fully implicit approximation method, in which the equations of continuity and momentum conservation are coupled through implicit summands of pressure gradient and mass flow. The method we propose removes severe restrictions on the time step and allows simulation of tsunami propagation to arbitrarily large distances. The landslide origin is simulated as an individual phase being a Newtonian fluid with its own density and viscosity and separated from the water and air phases by an interface. The basic formulas of equation discretization and expressions for coefficients are presented, and the main steps of the computation procedure are described in the paper. To enable simulations of tsunami propagation across wide water areas, we propose a parallel algorithm of the technique implementation, which employs an algebraic multigrid method. The implementation of the multigrid method is based on the global level and cascade collection algorithms that impose no limitations on the paralleling scale and make this technique applicable to petascale systems. We demonstrate the possibility of simulating all phases of a landslide-driven tsunami, including its generation, propagation and uprush. The technique has been verified against the problems supported by experimental data. The paper describes the mechanism of incorporating bathymetric data to simulate tsunamis in real water areas of the world ocean. Results of comparison with the nonlinear dispersion theory, which has demonstrated good agreement, are presented for the case of a historical tsunami of volcanic origin on the Montserrat Island in the Caribbean Sea.

Reliability of first-hand accounts on the study of historical tsunamis in northeastern Venezuela (southeastern Caribbean Sea)

The occurrence of tsunami waves on the eastern Caribbean Venezuelan coasts during 5 Venezuelan (local) earthquakes (01-IX-1530, 15-VII-1853, 29-X-1900, 17-I-1929 and 9-VII-1997), have been confirmed through the search and evaluation of written accounts by primary sources (eye witnesses) of tsunami inundation during these events. Among the outcomes of this new assessment are: 1) the run-up heights of several of those tsunamis have been substantially reduced. In fact, maximum run-up heights for the 5 tsunamis are: 5-7 m at Cumaná for the 1530 event, 5 m at Barlovento and 3 m at the Neverí mouth for the 1900 tsunami, 3 m at western Cumaná for the 1853 and 1929 events and about 1 m for the 1997 earthquake. 2) These new estimates on wave heights for local earthquakes restrict the search for tsunamites by trenching and coring to mainly the first 500-m-wide strip from the coastline in low-lying flatlands. The source of these tsunami waves may be complex. Some are surely the result of coastal-submarine sliding (1929 AD, 1997 AD), tectonic slip on active strike-slip (or normal oblique slip) faults (1530 AD, 1900 AD) or combination of tectonic slip and sliding (1853 AD). Appropriate numerical modeling of tsunami wave generation, migration and inundation are urgently in need to understand these tsunami mechanics.

An integrated Bayesian approach to the probabilistic tsunami risk model for the location and magnitude of earthquakes: application to the eastern coast of the Korean Peninsula

We explored the distributional changes in tsunami height along the eastern coast of the Korean Peninsula resulting from virtual and historical tsunami earthquakes. The results confirm significant distributional changes in tsunami height depending on the location and magnitude of earthquakes. We further developed a statistical model to jointly analyse tsunami heights from multiple events, considering the functional relationships; we estimated parameters conveying earthquake characteristics in a Weibull distribution, all within a Bayesian regression framework. We found the proposed model effective and informative for the estimation of tsunami hazard analysis from an earthquake of a given magnitude at a particular location. Specifically, several applications presented in this study showed that the proposed Bayesian approach has the advantage of conveying the uncertainty of the parameter estimates and its substantial effect on estimating tsunami risk.

Source of high tsunamis along the southernmost Ryukyu trench inferred from tsunami stratigraphy

Four paleotsunamis deposits are exposed in a trench on the coastal lowland north of the southern Ryukyu subduction zone trench. Radiocarbon ages on coral and bivalve shells show that the four deposits record tsunamis date from the last 2000yrs., including a historical tsunami with a maximum run-up of 30m in 1771, for an average recurrence interval of approximately 600yrs. Ground fissures in a soil beneath the 1771 tsunami deposit may have been generated by stronger shaking than recorded by historical documents. The repeated occurrence of the paleotsunami deposits supports a tectonic source model on the plate boundary rather than a nontectonic source model, such as submarine landslides. Assuming a thrust model at the subduction zone, the seismic coupling ratio may be as low as 20%.

Investigation of Offshore Fault Modeling for a Source Region Related to the Shakotan-Oki Earthquake

The purpose of this study is to verify fault modeling in the source region of the 1940 Shakotan-Oki earthquake using active faults offshore of Japan. Tsunami heights simulated in previous studies are found to be lower than observed levels, which makes it difficult to explain historical tsunami records of this earthquake. However, the application of appropriate slip magnitudes in the fault models may explain these differences. In the “Project for the Comprehensive Analysis and Evaluation of Offshore Fault Informatics (the Project),” a new fault model is constructed using marine seismic data and geological and geophysical data compiled by the Offshore Fault Evaluation Group, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) as part of the Project for Fault Evaluation in the Seas around Japan (Ministry of Education, Culture, Sports, Science and Technology, MEXT). Single-channel and multichannel reflection seismic data were used that includes information from a new fault identified in previous surveys. We investigated fault geometries and their parameters using the above data. Here, we show that the geometric continuity of these faults is adjusted by increasing the magnitude of fault slip. Standard scaling laws are applied on the basis of strong ground motion of the fault parameters, and the validity of the fault model is examined by comparing tsunami heights along the Japanese coastline from historically observed records with tsunami height from simulation analysis. This verification quantitatively uses Aida’s K and κ scale and variance parameters. We determine that the simulated tsunami height determined using the new model approach the heights observed historically, which indicates that the model is valid and accurate for the source region.