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.     

Tsunamis on the Russian Pacific coast: history and current situation

The Pacific coast, including the Kamchatka Peninsula, the Kuriles, the Sea of Japan, the Sea of Okhotsk, and the Bering Sea, is the main tsunami-prone area in Russia. The Far East tsunamis are much more frequent, extensive, and devastating than those in the Black, Caspian, Baltic, and White Sea coasts, as well as in major inland lakes of Baikal, Ladoga, etc. The tsunami catalog of the Russian Far East from 1737 to present lists 110 events with mainly near-field and few far-field sources (105 and 5 events, respectively). Most of the catalogued tsunamis (95 cases) were induced by earthquakes, and few events had volcanic (3), landsliding (2), meteorological (3), and unknown (2) triggers. Altogether there were eleven devastating tsunamis for the period of observations, with > 10 m heights, two of which were great events in 1737 and 1952, when the waves exceeded 20 m. The wave heights were in the range 2.5-10 m in fifteen hazardous tsunami events and within the tidal range (~ 1-2 m) in thirteen cases; the other events were small and detectable only instrumentally. Thus, the average recurrence times for tsunamis of different magnitudes in the Russian Pacific coast are 25 years for devastating events and 10-15 years for hazardous tsunamis; small tsunamis occur almost every year, according to statistics for the last sixty years collected at the regional network of tide stations. The topics discussed in the paper concern the completeness and reliability of the Far East catalog; distribution of tsunami events in space and time; correlation between the intensity of tsunami and the magnitude of the causative undersea earthquake; tsunami recurrence; tsunami warning; and long-term hazard assessment and mapping.     

Tsunami hazard in the Eastern Mediterranean: strong earthquakes and tsunamis in Cyprus and the Levantine Sea

A modern tsunami catalogue has been compiled for the region of Cyprus-Levantine Sea in which 24 certain or possible local tsunamis are listed from antiquity up to the present time, while six regional tsunamis, generated in the Hellenic arc, are documented which affected the region. Another set of 13 doubtful events not included in the catalogue are discussed. Tsunami intensities k and K were re-evaluated using the classic 6-grade and the new 12-grade intensity scales, respectively. The strongest tsunamis reported in the region of interest are those of 551 AD, 749, 1068, 1201, 1222, 1546 and 1759, all occurring along the Levantine coast from Gaza northward, with the exception of the 1222 wave which occurred in the Cyprean arc. The causative earthquakes, however, occur on land and are associated with the left-lateral strike-slip Levantine rift and, as such, remain unexplained. In this paper we speculate on the mechanism of these events. A second tsunami zone follows the Cyprean arc, where the situation of subaqueous seismogenic sources favours the generation of tsunamis by co-seismic fault displacements. Submarine or coastal earth slumping, however, may be an additional tsunamigenic component. Based on historical data, the average tsunami recurrence in the Cyprus-Levantine Sea region is roughly estimated to be around 30 years, 120 years and 375 years for moderate (k/K ≥ 2/3), strong (k/K ≥ 3/5) and very strong (k/K ≥ 5/8) events, respectively. The rate of tsunami occurrence equals 0.033, 8.3 × 10⁻³ and 2.7 × 10⁻³ events/year for intensity k/K ≥ 2/3, 3/5 and 5/8, respectively. For a Poissonian (random) process the probabilities of observing at least one moderate, strong or very strong tsunami are 0.28, 0.01 and 3 × 10⁻³ within 1 year, 0.81, 0.34 and 0.13 within 50 years and 0.96, 0.56 and 0.24 within 100 years, respectively. The tsunami potential in the Cyprus-Levantine Sea area is low relative to other Mediterranean tsunamigenic regions. However, the destructiveness of some historical events indicates the need to evaluate tsunami hazard by all available means. In addition, remote tsunamigenic sources, such as those of 1303 and 1481 in the eastern Hellenic arc, are able to threaten the coasts of the Cyprus-Levantine region and, therefore, such regional tsunamis should be taken into account in the evaluation of the tsunami risk of the region.     

南海古海啸重建与海啸沉积研究进展

中国东海、南海等近海临近琉球海沟、马尼拉海沟等俯冲带,地震频发.过去的海啸研究主要关注历史文献分析、海啸数值模拟等,据此评估中国近岸海啸灾害的历史和风险.历史时期是否引发了海啸,特别是具有特大致灾风险的大海啸记录,目前还不明确.近年来,本课题组通过对海岛、海洋沉积和海岸带及其岛屿的沉积过程、海啸遗迹和历史记录研究,阐述...     

Distribution Functions of Tsunami Wave Heights

The problem of describing the distribution functions of tsunami wave heights is discussed. Data on runup heights obtained in field surveys of several tsunamis for the last decade are used to calculate the empirical distribution functions. It is shown that the log-normal distribution describes the observed data well. This means that the irregular topography and coastline are major factors which influence the height distribution. The power distribution related with the geometric decay of the propagated wave is a good approximation for one event (Sulawesi, January 1, 1996) only. Results of a numerical simulation of the tsunami event in the Japan (East) Sea on July 12, 1993 are presented. It is shown that the computed wave height distribution, obtained by using the runup correction in the framework of nonlinear shallow-water theory, is in good agreement with the observed height distribution. Simulations are used to study the transformation of the distribution function on different distances from the source.     

Peculiarities of tsunamis generated by Asteroid impact or nuclear explosions in the northwest of Black Sea

Different models are used to evaluate the seashore effects of the tsunami generated by an asteroid impacting the shallow-water plateau in the northwest basin of the Black Sea. The shortest distance between the impact location and the coast is about 185 km. The tsunami’s effects on the coastal regions depend on many factors among which the most important is asteroid size. The tsunami generated by a 250-m asteroid reaches the nearest dry land location in 35 min and needs about 2 h to arrive all over the Black Sea coast. The run-up value is about 2 m high on Turkish and Crimean coasts. In the western Black Sea regions, the wave height is about 3 m. The run-up values strongly depend on bathymetry and topography peculiarities. The run-up values in case of the tsunami generated by a 1,000-m-sized asteroid are up to five to six times larger than in case of the 250-m impactor, depending on location. Differences between the tsunami’s dynamics on coastal regions situated in the proximity of deep water and shallow water, respectively, are outlined. Aspects concerning accidental or deliberate nuclear explosions are briefly referred. Possible social consequences and prevention are shortly discussed.     

Use of tsunami waveforms for earthquake source study

Tsunami waveforms recorded on tide gauges, like seismic waves recorded on seismograms, can be used to study earthquake source processes. The tsunami propagation can be accurately evaluated, since bathymetry is much better known than seismic velocity structure in the Earth. Using waveform inversion techniques, we can estimate the spatial distribution of coseismic slip on the fault plane from tsunami waveforms. This method has been applied to several earthquakes around Japan. Two recent earthquakes, the 1968 Tokachi-oki and 1983 Japan Sea earthquakes, are examined for calibration purposes. Both events show nonuniform slip distributions very similar to those obtained from seismic wave analyses. The use of tsunami waveforms is more useful for the study of unusual or old earthquakes. The 1984 Torishima earthquake caused unusually large tsunamis for its earthquake size. Waveform modeling of this event shows that part of the abnormal size of this tsunami is due to the propagation effect along the shallow ridge system. For old earthquakes, many tide gauge records exist with quality comparable to modern records, while there are only a few good quality seismic records. The 1944 Tonankai and 1946 Nankaido earthquakes are examined as examples of old events, and slip distributions are obtained. Such estimates are possible only using tsunami records. Since tide-gauge records are available as far back as the 1850s, use of them will provide unique and important information on long-term global seismicity.     

Detailing the impact of the Storegga Tsunami at Montrose,Scotland

The Storegga tsunami, dated in Norway to 8150±30 cal. years BP, hit many countries bordering the North Sea. Run-ups of >30 m occurred and 1000s of kilometres of coast were impacted. Whilst recent modelling successfully generated a tsunami wave train, the wave heights and velocities, it under-estimated wave run-ups. Work presented here used luminescence to directly date the Storegga tsunami deposits at the type site of Maryton, Aberdeenshire in Scotland. It also undertook sedimentological characterization to establish provenance, and number and relative power of the tsunami waves. Tsunami model refinement used this to better understand coastal inundation. Luminescence ages successfully date Scottish Storegga tsunami deposits to 8100±250 years. Sedimentology showed that at Montrose, three tsunami waves came from the northeast or east, over-ran pre-existing marine sands and weathered igneous bedrock on the coastal plain. Incorporation of an inundation model predicts well a tsunami impacting on the Montrose Basin in terms of replicate direction and sediment size. However, under-estimation of run-up persisted requiring further consideration of palaeotopography and palaeo-near-shore bathymetry for it to agree with sedimentary evidence. Future model evolution incorporating this will be better able to inform on the hazard risk and potential impacts for future high-magnitude submarine generated tsunami events.     

An extreme wave event in eastern Yucatán,Mexico: Evidence of a palaeotsunami event during the Mayan times

The Yucatán Peninsula, Mexico, has typically been considered a tectonically stable region with little significant seismic activity. The region though, is one that is regularly affected by hurricanes. A detailed survey of ca 100 km of the eastern Yucatán and Cozumel coast identified the presence of ridges containing individual boulders measuring >1 m in length. The boulder ridges reach 5 m in height and their origin is associated with extreme wave event activity. Previously modelled tsunami waves from known seismically active zones in the region (Muertos Thrust Belt and South Caribbean Deformed Belt) are not of sufficient scale in the area of the Yucatán Peninsula to have produced the boulder ridges recorded in this study. The occurrence of hurricanes in this region is more common, but two of the most destructive (Hurricane Gilbert 1988 and Hurricane Wilma 2005) produced coastal waves too small to have created the ridges recorded here. In this paper, a new tsunami model with a source area located on the Motagua/Swan Island Fault System has been generated that indicates a tsunami event may have caused the extreme wave events that resulted in the deposition of the boulder ridges.     

Building damage characteristics based on surveyed data and fragility curves of the 2011 Great East Japan tsunami

A large amount of buildings was damaged or destroyed by the 2011 Great East Japan tsunami. Numerous field surveys were conducted in order to collect the tsunami inundation extents and building damage data in the affected areas. Therefore, this event provides us with one of the most complete data set among tsunami events in history. In this study, fragility functions are derived using data provided by the Ministry of Land, Infrastructure and Transportation of Japan, with more than 250,000 structures surveyed. The set of data has details on damage level, structural material, number of stories per building and location (town). This information is crucial to the understanding of the causes of building damage, as differences in structural characteristics and building location can be taken into account in the damage probability analysis. Using least squares regression, different sets of fragility curves are derived to demonstrate the influence of structural material, number of stories and coastal topography on building damage levels. The results show a better resistant performance of reinforced concrete and steel buildings over wood or masonry buildings. Also, buildings taller than two stories were confirmed to be much stronger than the buildings of one or two stories. The damage characteristic due to the coastal topography based on limited number of data in town locations is also shortly discussed here. At the same tsunami inundation depth, buildings along the Sanriku ria coast were much greater damaged than buildings from the plain coast in Sendai. The difference in damage states can be explained by the faster flow velocities in the ria coast at the same inundation depth. These findings are key to support better future building damage assessments, land use management and disaster planning.     

A critical review of potential tsunamigenic sources as first step towards the tsunami hazard assessment for the Napoli Gulf (Southern Italy) highly populated area

Catastrophic tsunami events like those occurred in Papua New Guinea in 1998, Sumatra in 2004 and Japan in 2011, attracted the attention of the scientific community and promoted the development of different tools for assessing tsunami hazard. A preliminary step towards this goal is the knowledge of the events which might affect a specific coastal zone. In this context, we propose a method to identify the tsunami events possibly occurring in areas characterized by scarce data and a non-conservative environment. Accordingly, we propose different indices to summarize the knowledge on tsunami triggering mechanisms (earthquakes, landslides, volcanic eruptions), the characteristics of those mechanisms (magnitude of earthquakes, volume of landslide, Volcanic Explosivity Index) and tsunami features (water height, run-up, wave amplitude, propagation time). This knowledge, considered over a wider area than that of interest, allows for a paramount vision of possible hazardous events that could affect a particular coastal zone. Moreover, the tsunami simulation data and the analysis of potentially tsunamigenic slides which occurred on the Campania continental margins were also considered in the analysis. We focused our attention on Napoli megacity, because the high population density (about 1 million of people live on a territory of 117 km²), together with the presence of active volcanic areas (Ischia, Somma-Vesuvio and Campi Flegrei), make this city potentially exposed to tsunami risk. The main outcome of such an approach shows that in the near field a tsunami amplitude varying from a few centimetres (30–40 cm) to some metres (1–4 m) might be expected at the coastline if the tsunami event was triggered by volcanic activity, whereas no relevant tsunami event should be expected given the peculiar seismicity of the Neapolitan volcanic areas, with earthquakes rarely exceeding 4 Mw, if any possible cascade effects are overlooked. A morphometric analysis of high-resolution bathymetry collected between Ventotene Island and the Gulf of Salerno has shown that the submarine southern sectors of the Ischia Island and the Sorrento Peninsula are characterized by a high density of landslide scars, being thus a potential source area of landslide-generated tsunamis. However, despite the susceptibility of these areas to recurrent slope failures, only four submarine landslide scars were found to be potentially tsunamigenic with estimated tsunami amplitude of few metres at the coastline as predicted by coupling slide morphometry with tsunami amplitude equations. Concerning the tsunamis generated by earthquakes in the Western Mediterranean, only those triggered by high magnitude events (value ≥ 6–7 Mw) might affect the city of Napoli with an amplitude not exceeding 0.5 m, in about 30′.     

Laboratory study on tsunami erosion and deposition under protection of rigid emergent vegetation

Devastating tsunami waves can change the coastal morphology considerably. The effects of vegetation to coastal morphodynamics have been of primary interest for decades, because of their role in coastal protection and ecological environment. The damping of wave and impact of beach evolution are the two significant contributions on emerged vegetation. However, the laboratory study of tsunami erosion and deposition under protection of coastal vegetation was less understood compared to tsunami run-up and tsunami inundation. A set of laboratory experiments were reported in this study on changes of size-selective sandy beach profile under the protection of rigid emergent vegetation. The total of fifteen experiments was carried out in a wave flume including two initial profiles (with vegetation and none vegetation), three different wave conditions and four forest densities. The experiments show that rigid emergent vegetation changes the depth and location of tsunami deposition and erosion in sandy beach. The dimensionless numbers were derived to characterize the cross-shore beach profile response under the protection of rigid emergent vegetation. These parameters were written as a dimensionless group, and based upon this present experimental datum, the empirical equations were developed. The study reveals the internal connection among tsunami deposition and erosion, wave height and forest density. The findings of this study have the potential to assist the tsunami hazards prevention and mitigation.     

Simplified formulae for designing coastal forest against tsunami run-up: one-dimensional approach

In the present study, laboratory experiments were conducted to validate the applicability of a numerical model based on one-dimensional nonlinear long-wave equations. The model includes drag and inertia resistance of trees to tsunami flow and porosity between trees and a simplified forest in a wave channel. It was confirmed that the water surface elevation and flow velocity by the numerical simulations agree well with the experimental results for various forest conditions of width and tree density. Further, the numerical model was applied to prototype conditions of a coastal forest of Pandanus odoratissimus to investigate the effects of forest conditions (width and tree density) and incident tsunami conditions (period and height) on run-up height and potential tsunami force. The modeling results were represented in curve-fit equations with the aim of providing simplified formulae for designing coastal forest against tsunamis. The run-up height and potential tsunami forces calculated by the curve-fit formulae and the numerical model agreed within ± 10% error.     

Historical tsunami records and potential tsunami scenarios near Haikou coastal region

Historical tsunami records in the South China Sea are collected and analyzed in this paper. There have been about 54 tsunamis in the South China Sea since 1076. The impacts of the transoceanic tsunamis on the southeast coast of China are weak. However, the regional tsunamis in the South China Sea bring varying degrees of influence to the south coast of China, which occurred about 18 times. By the analysis of the potential tsunami sources in the South China Sea, numerical simulations of tsunami induced in the Manila Trench are carried out. It is found that the tsunami wave height is small near Haikou if the general earthquake tsunami occurred. But the tsunami wave height is large when a giant earthquake of M9.3 occurred. If this extreme situation arises, the impacts to the coast of Haikou will be serious.     

Historical tsunamis in the Adriatic Sea

Tsunami activity in the Adriatic Sea from the sixteenth century until the present has been analysed with the ultimate goal to improve the European tsunami catalogue and provide data for a new geo-database of tsunami events in the European-Mediterranean region. The study encompasses twenty-seven events, nine on the western and eighteen on the eastern coast of the Adriatic, with special attention being devoted to contemporary sources and to local journals and newspapers. For all the analysed events, the path of information from coeval sources, through the nineteenth century and up to modern tsunami catalogues, has been constructed. Tsunamis on the western coast have already been studied, but to obtain a coherent picture of tsunamigenic activity in the Adriatic Sea, they have been included in this work. Furthermore, the study was extended to see whether they had propagated to the opposite coast. Most of the events on the eastern coast have now been systematically analysed for the first time. The search of bibliographical sources revealed three new reports on tsunamis on the eastern coast that had not been previously recorded in international publications. The study established that, out of the eighteen eastern Adriatic events, twelve can be considered false, while six were true tsunamis. In the last 600 years, fifteen true tsunami events occurred in the Adriatic. One was very strong, six were strong or rather strong, and eight were light tsunamis. As a final result of this analysis, carried out according to standardised criteria, fifteen Adriatic tsunami events will be inserted in the TRANSFER (Tsunami Risk ANd Strategies For the European Region) database for the European-Mediterranean region.     

Tsunami simulation due to seaquake at Manila Trench and Sulu Trench

Seaquake is a phenomenon where there are water disturbance at the sea, caused by earthquake or submarine eruption. The scope of this study focuses on tsunami simulation due to Manila Trench and Sulu Trench seaquake which is prone to harm Malaysia offshore areas. Manila Trench is a highly potential earthquake source that can generate tsunami in South China Sea. Meanwhile, Sulu Trench could be a threat to east of Sabah offshore areas. In this study, TUNA-M2 model was utilized to perform tsunami simulation at South China Sea and Sulu Sea. TUNA-M2 model applied Okada source model to create tsunami generation due to earthquake. It utilized linear shallow water equation during tsunami propagation with its radiant boundary condition. Five simulations performed at each study region. Forecast points at South China Sea areas were divided into three separate locations which are at the Peninsular Malaysia, west of Sabah and Sarawak offshore areas. Forecast points at Sulu Sea were focused at the east of Sabah offshore areas. This paper will present the simulation results of tsunami wave height and arrival time at various forecast points. The findings of this study show that the range of tsunami wave height at Sulu Sea is higher than that of South China Sea. The tsunami arrival time at Sulu Sea is less than South China Sea. It can be concluded that Sulu Sea poses worse tsunami threat than South China Sea to the Malaysian offshore areas.     

Study on potential tsunami by earthquake in subduction zone of Sulawesi Sea

Indonesia is one country in the world featuring a complex tectonic structure. This condition makes earthquakes often occur in many areas of this country and as an earthquake rages beneath the sea, it will potentially trigger tsunami. One of the areas in Indonesia with a high seismic activity is Sulawesi region particularly in the Sulawesi Sea subduction zone, making it important to carry out a study on the potential tsunami at this location. The purpose of this study was to analyze the existing huge potential energy in Sulawesi Sea subduction zone and to identify tsunami modeling likely to occur based on the potential energy of the region. The approach used in assessing the tsunami disaster was the calculation of the potential energy of an earthquake and tsunami modeling based on the potential energy. The method used in this research was the least squares method for the calculation of potential energy, and near-field tsunami modeling with the assistance of TUNAMI-N2 COD. The research finding has shown that the Sulawesi Sea subduction zone has potential energy of 1.35469?×?10²³ erg, equivalent to an earthquake with a magnitude of 7.6 Mw. The tsunami modeling made shown the average wave propagation reaching ashore within 12.3 min with a height varying between 0.1 and >?3 m. The tsunami modeling also indicated that there are seven sub-districts in Buol District, Central Sulawesi, which is affected by a significant tsunami.     

海底滑坡海啸的颗粒流耦合模型

海底滑坡的运动可能引发海啸,破坏离岸设施,威胁海岸带安全。国内外关于海底滑坡引发海啸的研究方兴未艾。采用Mih颗粒流模型控制具弱黏聚力的砂土滑坡运动,利用两相流模型计算岩土体-水体相互作用及RNG湍流模型控制水体运动,构建了基于颗粒流模型的海底滑坡海啸全耦合数值分析方法。通过简单水槽水下滑坡案例进行了海底滑坡海啸全过程研究。数值分析再现了变形滑体的不均一运动、密度分异流动、水滑机制和以波谷为典型特征的涌浪波等典型海底滑坡及海啸现象,这表明数值模型具有有效性。许多海域（包括中国南海北部）都存在弱黏聚力和无黏聚力的水下滑坡,该数值方法值得推广和进一步研究完善。     

Analysis of the global tsunami data for vulnerability and risk assessment

For the assessment of tsunami risk and vulnerability, one has to make use of past tsunami observations. The most comprehensive tsunami databases for the world have been prepared by the National Geophysical Data Center of USA which are listed on their website for all the four oceans as well as the following marginal seas: Caribbean Sea, Mediterranean Sea, Black Sea, Red Sea and Gulf of Mexico. The dataset goes back as far as the first century AD and lists the events on a confidence rating scale of 0–4; 0 being an erroneous entry and 4 being a definite tsunami. Based on these various datasets for different geographical areas, a comprehensive global dataset was prepared in this study, which included only tsunami events with confidence rating of 3 and 4, meaning either probable or definite. In this composite and abridged global tsunami database there is no distinction either according to geography or tsunami strength as implied by its impact on the coast. A simple and straightforward statistical analysis suggests an almost complete randomness and no patterns that can be used for future tsunami predictions with a few minor exceptions.