Search

South America's Pacific margin is subject to recurring subduction-zone earthquakes that have generated devastating historical tsunamis, as well as earlier events impacting indigenous populations that have lived along the region's rich upwelling coastlines throughout the Holocene. Despite recurring events, the geologic record of paleo-tsunamis is relatively sparse. Here we report evidence for two paleo-tsunamis striking the Chicama River coastline (8°S) around 2.8 and 2.0 ka. The two sedimentary deposits are amalgamated in many locations and can be difficult to distinguish, but floodplain or shoreface deposits separate the two units when traced landward and seaward, respectively. The magnitude of each event was sufficient to erode coarse cobbles (13–25 cm) from the shoreface and transport them ~100 m before being deposited as rapidly thinning and fining gravel units. Based on the distribution of mobilized cobbles, we consider plausible flow characteristics for the two tsunamis suggesting that each was on the order of at least a few meters in height with most of the cobble transport occurring only under critical to supercritical flow at the wave front. Previous archaeological reports from the area correctly recognized the older tsunami event but did not describe the younger, better-preserved second event. Further, we revisit the archaeological evidence for the tsunami and recast the older event as likely being more moderate than previously suggested. Broader archaeological evidence from this 30-km reach of the Chicama valley shoreline also suggests that the late Cupisnique to Salinar and Gallinazo cultures were not severely disrupted by the tsunamis, even with these events undoubtedly impacting nearshore inhabitants at the time. [ABSTRACT FROM AUTHOR]

This study proposes a stochastic approach to assess the future tsunami potential globally, focusing on the inter-arrival time of tsunami events in the 14 most active tsunamigenic zones. Two methods, conditional probability (CP) and the total probability theorem (TPT), were employed to estimate tsunami potential. For CP, the occurrence of a tsunami over time was determined by selecting the best-fit stochastic model (Gamma, Lognormal, Weibull, or log-logistic distributions) based on the time of the last earthquake in each zone. In contrast, TPT calculated the probability as the product of the tsunami-to-earthquake ratio ‘r’ and the CP of the time zone [P (E)]. However, direct comparison between the probabilities obtained by the two methods proved challenging due to the maximum value ‘r’ can attain for a region in TPT. In contrast, CP values may extend to 1 over a longer period. The study evaluates the probability of future tsunami occurrences under two conditions: mixed tsunamis (any wave height) and tsunamis with wave heights exceeding 3 m. Zones with higher likelihoods of tsunami occurrences for both scenarios are identified and highlighted. The obtained probabilities were validated against respective zone threshold probabilities. Additionally, TPT-derived probabilities for tsunamis under mixed conditions reveal higher likelihoods in Zone 1 (Colombia, Ecuador, Brazil), succeeded by Zone 7 (Japan, China, North Korea), and Zone 11 (Solomon Islands, Vanuatu, New Caledonia). Conversely, the probability of tsunamis with wave heights exceeding 3 m is higher in Zone 3 (Cuba, Jamaica, Haiti), followed by Zone 9 (Malaysia, Brunei, Australia), and Zone 1 (Colombia, Ecuador, Brazil). These variations stem primarily from spatial changes in the global tsunami-to-earthquake ratio across distributed zones. This study contributes to a more comprehensive understanding of future tsunami potential, aiding decision-makers and planners in taking informed actions to mitigate potential risks. [ABSTRACT FROM AUTHOR]

On January 1, 2024, an earthquake of magnitude 7.6 struck the Noto Peninsula in Ishikawa Prefecture, Japan. Tsunamis were recorded along nearby coasts following the earthquake, with the early tsunami arrival time at the Toyama tide station—located far from the earthquake epicenter—indicating potential submarine landslides in Toyama Bay. To identify these potential submarine landslides by detecting changes in seafloor depth, we collected new bathymetric data using a multibeam echo sounder in January and February 2024, and then compared them with data collected in 2010. This bathymetric comparison revealed submarine landslides along a submarine canyon off the Jinzu River, covering an area measuring 3.5 km × 1 km at depths of 40–370 m. Slide relief ranged from several meters up to 40 m, with some slides displaying distinct head scarps. Seafloor observations in areas with minor depth changes confirmed the presence of cliffs, disturbed seabed, and a redox boundary on the disturbed oxide layer, indicating recent landslides. Given the slide distribution within the estimated tsunami source area of the 2024 Noto Peninsula Earthquake, it is likely these slides were triggered by the earthquake. [ABSTRACT FROM AUTHOR]

This paper presents a review of prediction models for tsunami-induced lateral fluid forces or tsunami-wave forces for the next revision of the engineering design code for nuclear power plant structures. First, research on the characteristics and prediction models of tsunami wave forces or pressure on the dry- and wet-bed structures is reviewed. The prediction models adopted in Japanese and US design guidelines for buildings and coastal facilities are presented. Finally, the prediction models adopted in the Japanese engineering design code for nuclear power plant structures are described, and items that should be added or considered for the next revision of the code are discussed. Based on our discussions against the review, the revised code should include the relationship between the Froude number and tsunami-wave force or pressure, and the conservatism of each prediction model should be carefully considered. The comprehensive review in this study should be useful not only for the next revision of JEAC 4629, but also as a reference for the development of guidelines for tsunami-resistant designs in countries where tsunamis are a threat. [ABSTRACT FROM AUTHOR]

Tsunamis are devastating natural hazards that can reach runups of 30 m in coastal areas. One of the most important mitigation measures to save human lives is evacuation, which requires identification of both the inundation area and safe zones. Currently, a ground elevation of 30 m is used to determine safe zones in Chile. However, it has also been used for urban planning, for which the actual tsunami hazard may be overestimated. This research aims to propose a criterion based on probabilistic analysis to determine the tsunami inundation limit, considering both the runup and inundation distance from the shoreline. To this end, a synthetic database of runup and inundation distance from the shoreline was analyzed. First, stochastic earthquake sources were used to simulate tsunami events up to an inundation level in 10 coastal cities. Second, maximum runup and inundation distance were calculated for each tsunami scenario along transect lines perpendicular to the coastline. Finally, three exceedance probabilities of runup – 0.5%, 1%, and 2% in 50 years – were calculated to estimate the runup and inundation distances for each city. The results showed that geomorphology has an important role in runup and inundation distance. In addition, this research introduced new criteria for inundation limit identification, which are more flexible and accurate than the current 30-m ground elevation criterion used for tsunami risk assessment and urban planning. The application of this proposed method would allow local authorities to improve the locations of both critical infrastructure and safe zones. [ABSTRACT FROM AUTHOR]

Seawater intrusion into soils caused by global climate change and tsunami disasters is a significant factor contributing to soil salinization in coastal vegetation areas, posing a critical threat to agriculture and food security. This study aimed to evaluate the seawater tolerance of Vigna marina, a wild Vigna species, through comparative laboratory experiments with Vigna radiata (mung bean) and Vigna angularis (adzuki bean). Unlike V. radiata and V. angularis, the seeds of V. marina exhibited significant buoyancy in seawater, remaining afloat for at least 30 days. After this prolonged seawater incubation, V. marina seeds maintained a 100% germination rate, whereas V. radiata and V. angularis failed to germinate under the same conditions. The photosynthetic activity of V. marina seedlings, evaluated via the Fv/Fm parameter, remained stable even after seven days of seawater irrigation. In contrast, V. radiata and V. angularis perished under seawater irrigation. Furthermore, V. marina seedlings exhibited sustained growth under seawater irrigation, showing consistent increases in both fresh and dry weight. These findings confirm that V. marina possesses remarkable tolerance to seawater, a critical characteristic for cultivation in areas affected by seawater intrusion. [ABSTRACT FROM AUTHOR]

The rubble mound (RM) breakwater, which is a prevalent coastal structure worldwide, often faces the significant challenge of tsunami-induced damage. Coastal regions which are characterized by high population density necessitate robust breakwaters to withstand the destructive forces of tsunamis. The most devastating natural hazard that a breakwater could encounter during its lifespan is the tsunami. Past occurrences have revealed vulnerabilities in conventional RM breakwaters leading to failures attributed to the scouring of rubble and seabed caused by excessive seepage during tsunami overflow events. This study presents novel countermeasures aimed at mitigating the potential failure mechanisms induced by tsunamis on RM breakwaters. The proposed countermeasure elements include gabions, crown walls equipped with shear keys, and sheet piles. To assess the efficacy of these innovations, a series of tsunami overflow tests was conducted on small-scale models. The results demonstrated a marked improvement in the stability and resilience of RM breakwaters against tsunamis with the incorporation of these countermeasures. Additionally, numerical simulations were performed to determine the precise mechanisms influencing the behavior of the breakwater during tsunamis. Practical Applications: This study introduces innovative techniques for enhancing the resilience of rubble mound breakwaters against tsunamis, which have significant implications for coastal protection and disaster mitigation efforts worldwide. By incorporating gabion-based countermeasures such as wire cages filled with rocks (gabions), crown walls with shear keys, and sheet piles, substantial improvements were observed in the stability and durability of rubble mound breakwaters during tsunami events. The proposed technique enabled the rubble mound breakwater to withstand Level 1 tsunamis without undergoing any deformations. For coastal communities facing the threat of tsunamis, implementing the proposed novel gabion-based techniques offers tangible benefits in terms of enhanced protection against catastrophic tsunamis. The proposed technique provides cost-effective and adaptable solutions to existing and newly constructed rubble mound breakwaters. Through practical application of the proposed technique, coastal engineers, policymakers, and disaster management agencies can effectively mitigate the risks posed by tsunamis. [ABSTRACT FROM AUTHOR]

In this study, uncertainty quantification and parametric sensitivity analysis in Probabilistic Tsunami Hazard Assessment (PTHA) are performed for the South China Sea using a Monte Carlo approach. Uncertainties in parameters such as the magnitude–frequency distribution of the potential tsunami zone, geodetic information used to constrain the maximum magnitude, properties determining the slip distribution, scaling laws and dip of unit sources are considered, each of which is varied separately while the others are fixed. The Coefficient of Variation (COV) of tsunami amplitudes corresponding to a fixed annual probability at different coastal sites is used to represent the uncertainty of each parameter. In addition, the overall tsunami hazard and uncertainty are also presented by simultaneously varying all parameters in a Monte Carlo series. Our results suggest that a major contributor to the uncertainty is the magnitude frequency distribution parameters, especially the maximum magnitude. Geodetic information can be used to solve the problem that the maximum magnitude is underestimated owing to the scarcity of mega earthquakes in the historical earthquake catalog, while it will also lead to a large uncertainty if the parameters in it are not well determined. Among these geodetic parameters, the seismic coupling coefficient is the parameter that most influences the uncertainty as it is difficult to determine an accurate value. The effect of the slope parameter β in the magnitude–frequency relationship is complicated because of its influence in determining the maximum magnitude and the number of earthquake events. In addition, the uncertainty associated with the down-dip width of the seismogenic zone is not remarkable but cannot be ignored, which is similar to that of the annual plate slip rate, while the effect of the rigidity is relatively small because its effect on the average slip of earthquake events will reduce the uncertainty. Compared to the uncertainty in determining the maximum magnitude, the effect of slip distribution properties such as Hurst exponent, correlation length and scaling exponent and the choice of scaling laws is relatively small. The uncertainty in the dip angle of the unit source is moderate and cannot be ignored, especially for sites along the strike of the subduction zone. Tsunami curves for four coastal sites indicate that the tsunami hazard in the South China Sea is subject to large variations when considering all uncertainties in the PTHA, with the COV in 2000 years at different sites being about 0.25, which means that the 95th percentile is about two times of the 5th percentile. [ABSTRACT FROM AUTHOR]

We study a linear model for the propagation of acoustic and surface gravity waves in a stratified free-surface ocean. A formulation was previously obtained by linearizing the compressible Euler equations. In this paper, we introduce a new formulation written with a generalized potential. The new formulation is obtained by studying the functional spaces and operators associated to the model. The mathematical study of this new formulation is easier and the discretization is also more efficient than for the previous formulation. We prove that both formulations are well-posed and show that the solution to the first formulation can be obtained from the solution to the second. Finally, the formulations are discretized using a spectral element method, and we simulate tsunamis generation from submarine earthquakes and landslides. [ABSTRACT FROM AUTHOR]

Copyright of REDER: Revista de Estudios Latinoamericanos sobre Reducción del Riesgo de Desastres is the property of Corporacion Gestion de Riesgos y Desastres (GRID-Chile) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding the vulnerability of school shelters to tsunamis is crucial for developing effective mitigation strategies and increasing the resilience of coastal communities in the education sector. SDN 02 Sasak Ranah Pasisia, an elementary school in West Pasaman Regency, West Sumatera, Indonesia, had a shelter building constructed in 2010. However, the construction remains incomplete. A structural assessment using current Indonesian building codes and vulnerability analysis is necessary to proceed with construction and ensure the building's strength against the working loads. Thestructural assessment revealed that several columns could not support the working load, necessitating local retrofitting. In this study, the retrofitting of the building was designed using concrete jacketing. Furthermore, structural fragility curves of the school building were developed before and after retrofitting against earthquake and tsunami loads. The seismic fragility curve was determined from the maximum displacement of the building for varied earthquake acceleration, using nonlinear time history dynamic response analysis scaled using the incremental dynamic analysis method and damage limits defined by ATC-40, characterized by Hazus. Meanwhile, the tsunami fragility curve was determined from the maximum displacement due to tsunami load for each variation of tsunami inundation depth. The vulnerability analysis results indicated that retrofitting the school building with concrete jacketing reduces the probability of building damage due to earthquake loads by 18% at the level of complete damage at a PGA of 0.520 g (based on the Indonesian Seismic Map). Similarly, it reduced the probability of building damage due to tsunami loads by 20%, at the level of complete damage corresponding to a tsunami wave height of 5.00 m for West Pasaman, Indonesia. [ABSTRACT FROM AUTHOR]

An analysis of internal waves arising in a two-layer fluid during an explosive eruption of an underwater volcano is performed. Processes occurring in the near zone are parameterized by the initial source in the form of a displacement of the water column, as proposed by Le Méhaute (Mehaute, Adv Hydrosci 7:1–79, 1971). Then the linear problem is solved, and the features of internal waves are determined depending on the ratio of layer thicknesses, source radius, and distance to the source. The calculated wave field has the form of frequency-modulated groups, where the leading group has the maximum amplitude. The wave of maximum height in this train arrives much later than the weak leading wave, which makes it possible to prepare for the approach of dangerous waves. Estimates of the horizontal speed of currents on the sea surface caused by internal waves have been carried out. It was shown that internal waves can cause noticeable variations in wind ripples detected by remote sensing. [ABSTRACT FROM AUTHOR]

This study focuses on the risks that tourists would face during a tsunami on the island of Stromboli and discusses how to best inform and prepare them. Tsunamis affect coastal regions, where many of these are leisure destinations for tourists who often don't have adequate knowledge of the region's risks. Due to their proximity to the affected areas, near-source or local tsunamis usually allow for a limited warning time, posing great challenges to the planning of effective risk mitigation action. Furthermore, tourist populations have a particular significance in studies on risk perception, since their needs intersect with those of the local population and must be taken into account. To gather key knowledge for developing robust risk communication strategies, a survey (n = 699) was conducted between July and October 2023 to assess tourists' risk perception and preparedness. The findings indicate that tourists often misdescribe tsunamis, leading to underestimation of the security threats posed by smaller events and revealing shortcomings in current communication approaches. Given the tourism industry practices on the island, effective communication strategies for tourists should prioritize providing comprehensive information within the first 24 h of their arrival. Furthermore, given the high percentage of tourists who visit the island for a few hours and within certain time slots, we invite the authorities to provide this information before disembarking on the island. [ABSTRACT FROM AUTHOR]

The 2018 Sulawesi Earthquake and Tsunami serves as a backdrop for this work, which employs simple and straightforward remote sensing techniques to determine the extent of the destruction and indirectly evaluate the region's vulnerability to such catastrophic events. Documenting damage from tsunamis is only meaningful shortly after the disaster has occurred because governmental agencies clean up debris and start the recovery process within a few hours after the destruction has occurred, deeming impact estimates unreliable. Sentinel-2 and Maxar WorldView-3 satellite images were used to calculate well-known environmental indices to delineate the tsunami-affected areas in Palu, Indonesia. The use of NDVI, NDSI, and NDWI indices has allowed for a quantifiable measure of the changes in vegetation, soil moisture, and water bodies, providing a clear demarcation of the tsunami's impact on land cover. The final tsunami inundation map indicates that the areas most affected by the tsunami are found in the urban center, low-lying regions, and along the coast. This work charts the aftermath of one of Indonesia's recent tsunamis but may also lay the groundwork for an easy, handy, and low-cost approach to quickly identify tsunami-affected zones. While previous studies have used high-resolution remote sensing methods such as LiDAR or SAR, our study emphasizes accessibility and simplicity, making it more feasible for resource-constrained regions or rapid disaster response. The scientific novelty lies in the integration of widely used environmental indices (dNDVI, dNDWI, and dNDSI) with threshold-based Decision Tree classification to delineate tsunami-affected areas. Unlike many studies that rely on advanced or proprietary tools, we demonstrate that comparable results can be achieved with cost-effective open-source data and straightforward methodologies. Additionally, we address the challenge of differentiating tsunami impacts from other phenomena (et, liquefaction) through index-based thresholds and propose a framework that is adaptable to other vulnerable coastal regions. [ABSTRACT FROM AUTHOR]

The stability of the waterfront retaining walls is critical while subjected to the combined actions of a tsunami and earthquake. Although rare, simultaneous occurrences remain critical for prominent structures. However, the design criteria for this coupled action are available only for waterfront retaining walls with a vertical or inclined backface. The current study presents the seismic design and stability analysis of a waterfront retaining wall with a commonly used bilinear backface subjected to tsunamis and earthquakes by employing a limit equilibrium approach coupled with a pseudodynamic method for a passive state. The factor of safety reduces by 83%–99% for sliding and overturning when waterfront retaining walls are subjected to the combined forces of an earthquake and tsunami rather than an earthquake alone. Suitable design charts with factors of safety for sliding and overturning are presented for various parameters such as tsunami wave height, depth of water at the seaward side, height of submergence, excess pore pressure ratio, and wall inclination, which certainly facilitates the optimum construction of a waterfront retaining wall with a bilinear backface. [ABSTRACT FROM AUTHOR]

The consequences of natural hazards like tsunamis often lead to severe damage to coastal bridges, resulting in socioeconomic loss, delays in rescue operations, and even loss of human lives. It is therefore important to quantify the vulnerability and improve the resilience of coastal bridges subjected to tsunami loading using advanced construction materials. This paper is the first-ever attempt to study the potential of the nickel–titanium shape memory alloy (Ni-Ti SMA) reinforcement in enhancing the resilience of reinforced concrete coastal bridges exposed to tsunami loads. The load modeled included drag, inertia, and slamming components. The impact of time-varying debris load associated with the tsunami waves was also analyzed. Under three representative wave periods, several combinations of wave heights were considered as the variable intensity measures for the fragility and resiliency assessments. The analysis results showed that the Ni-Ti SMA reinforcement in the plastic hinge region allows the piers to sustain higher drifts before significant damage compared to the conventional steel-reinforced piers. Moreover, the SMA-reinforced piers exhibited lower fragility and functionality loss under tsunami loads having wave periods greater than 5.50 s. [ABSTRACT FROM AUTHOR]