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New Makran simulations imply two generalized zones of mid-field tsunami hazard in greater Karachi. The simulations presuppose seven megathrust ruptures that strike east-west, range in area from 100 × 150 km to 355 × 800 km, and lie west of the city by no less than 100 km. The assumed seismic slip is uniform across each rupture area. The smallest rupture approximates the 1945 Makran earthquake of magnitude 8.1, while the largest corresponds to a previously conjectured giant Makran earthquake of magnitude 9.2. None of the sources include a complication in 1945: late-arriving waves from submarine slides or splay faulting. Consequently, the first simulated wave is the largest in each of the seven scenarios. And because the sources are to the west, the simulated waves are higher, and arrive sooner, at Karachi Port (1.5 hr) than 30 km farther east at Port Qasim (nearly 3 hr). These combinations of height and arrival time can be generalized as properties of two hazard zones: a western one that includes Karachi Port, and an eastern one that includes Port Qasim. The simulated flooding extends farthest inland into low-lying residential areas of the western zone. Neither hazard zone is near-field or far-field. That is, neither is near enough to the fault ruptures for felt seismic shaking to dependably warn of a fast-arriving tsunami, yet neither is distant enough to receive more than three hours of advance notice through tsunami warning systems. Our simulations are intended to support emergency management in this mid-field setting. [ABSTRACT FROM AUTHOR]

Estimating coastal tsunami impact for early-warning or long-term hazard analysis requires the calculation of inundation metrics such as flow-depth or momentum flux. Both applications require the simulation of large numbers of scenarios to capture both the aleatory variability and the epistemic tsunami uncertainty. A computationally demanding step in simulating inundation is solving the non-linear shallow water (NLSW) equations on meshes with sufficiently high resolution to represent the local elevation accurately enough to capture the physics governing the flow. This computational expense is particularly challenging in the context of Tsunami Early Warning where strict time constraints apply. A machine learning (ML) model that predicts inundation maps from offshore simulation results with acceptable accuracy, trained on an acceptably small training set of full simulations, could replace the computationally expensive NLSW part of the simulations for vast numbers of scenarios and predict inundation rapidly and with reduced computational demands. We consider the application of an encoder–decoder based neural network to predict high-resolution inundation maps based only on more cheaply calculated simulated time-series at a limited number of offshore locations. The network needs to be trained using input offshore time-series and the corresponding inundation maps from previously calculated full simulations. We develop and evaluate the ML model on a comprehensive set of inundation simulations for the coast of eastern Sicily for tens of thousands of subduction earthquake sources in the Mediterranean Sea. We find good performance for this case study even using relatively small training sets (order of hundreds) provided that appropriate choices are made in the specification of model parameters, the specification of the loss function and the selection of training events. The uncertainty in the prediction for any given location decreases with the number of training events that inundate that location, with a good range of flow depths needed for accurate predictions. This means that care is needed to ensure that rarer high-inundation scenarios are well-represented in the training sets. The importance of applying regularization techniques increases as the size of the training sets decreases. The computational gain of the proposed methodology depends on the number of complete simulations needed to train the neural network, ranging between 164 and 4196 scenarios in this study. The cost of training the network is small in comparison with the cost of the numerical simulations and, for an ensemble of around 28 000 scenarios, this represents a 6- to 170-fold reduction in computing costs. [ABSTRACT FROM AUTHOR]

This study provides a dataset and shows the spatial distribution of tsunami hazard in the South China Sea sourced from the Manila subduction zone. The plate motion data around the Manila subduction zone are used to invert the geodetic locking of the Manila subduction zone, further used to estimate the maximum possible magnitude and applied to obtain a more reliable tsunami hazard assessment. The spatial distribution of tsunami wave height with a 1000-year return period is shown, and several high-hazard areas in the South China Sea are pointed out. Uncertainties in the seismic source are explored, including the slip heterogeneity, the upper limit of seismic magnitude and segmentation. The impact of the locking distribution and randomness of slip on tsunami hazard assessment demonstrates that the traditional uniform slip assumption significantly underestimates the tsunami hazard. Moreover, the assessment results involving the effect of the locking distribution should be more realistic and show a larger tsunami height than when only considering the stochastic slip in most areas, which should prompt coastal management agencies to enhance tsunami prevention awareness. [ABSTRACT FROM AUTHOR]

Earthquakes in coastal areas frequently trigger tsunami waves, posing significant threats to low-lying coastal bridges. Investigating extreme wave force on bridge deck is crucial for understanding bridge damage mechanisms. However, the majority of current research focuses on single bridge deck, with limited analysis of wave impacts on twin bridge decks. In this paper, solitary wave is utilized to simulate tsunami wave, and a two-dimensional (2D) computational fluid dynamics (CFDs) model to analyze wave–bridge interactions and investigate the impact of tsunami wave on adjacent twin box-girder bridge decks. The numerical model was validated by solitary wave theory and wave force data obtained from the published experiment. Based on this model, the effects of the submergence coefficient, wave height, and deck spacing on the horizontal and vertical forces on the twin box-girder bridge decks were analyzed and compared with those in a single box-girder bridge deck. The results indicate that, firstly, due to wave reflection and the trapped water, the vertical wave force on the twin forward bridge deck significantly surpasses that on the single bridge deck. Furthermore, the twin backward bridge deck experiences greater horizontal force than single deck when the deck is completely submerged. Secondly, the maximum wave force on the twin bridge decks does not always consistently decrease with increasing deck spacing. Finally, the negative horizontal force would exceed the positive horizontal force on the twin forward bridge deck under higher wave. This paper delineates the disparities between twin and single box-girder bridge deck responses to wave action and analyzes the influencing factors. Such insights are pivotal for coastal bridge construction and natural disaster risk assessment. [ABSTRACT FROM AUTHOR]

The initial condition for the simulation of a seismically-induced tsunami for a rapid, assumed instantaneous, vertical seafloor displacement is given by the Kajiura low-pass filter integral. This work proposes a new efficient and accurate approach for its numerical evaluation, valid when the sea floor displacement is discretized as a set of rectangular contributions. We compare several truncated quadrature formulae, selecting the optimal one. We verify that we can satisfactorily approximate the initial sea level perturbation as a linear combination of those induced by the elementary sea floor displacements. The methodology is tested on the tsunamigenic Kuril earthquake doublet – a megathrust and an outer-rise – occurred in the Central Kuril Islands in late 2006 and early 2007. We also confirm the importance of the horizontal contribution to the tsunami generation and we consider a simple model of the inelastic deformation of the wedge, on a realistic bathymetry. The proposed approach results accurate and fast enough to be considered relevant for practical applications, and a tool is provided to create tsunami unit source databases for a given region of interest. [ABSTRACT FROM AUTHOR]

Background: The Mediterranean Sea is a region characterized by high seismic activity, with at least 200 tsunami events recorded from the fourth century to the present twenty-first century. Numerous studies have been conducted to understand past tsunami events, earthquake–tsunami generation, tsunami recurrence periods, tsunami vulnerability zones, and tsunami hazard mitigation strategies. Therefore, gaining insights into future trends and opportunities in Mediterranean Sea tsunami research is crucial for significantly contributing to all relevant aspects. This study aims to assess such trends and opportunities through a scientometric analysis of publications indexed by Web of Science from 2000 to 2023. Results: Based on a selection of 329 publications, including research articles, review articles, book chapters, and conference papers, published between 2000 and 2023, Italy has the highest number of publications and citations in this field. The number of publications has increased significantly, especially after the 2004 Indian Ocean, 2011 Tohoku, and 2018 Palu tsunamis. According to the keyword analysis, the terms "tsunami", "earthquake", "hazard", "wave", "Mediterranean", "coast", and "tectonic" were the most frequently used in these publications. Research themes consist of four classifications: motor themes, such as seismic hazard; specific but well-developed themes, like tsunamiite; emerging or disappearing themes, for example, climate change; and general or basic themes, such as equations and megaturbidite. The number of publications related to the motor theme classification continued to grow throughout 2000–2023. Topics from 2011–2023 are more complex compared to 2000–2010, characterized by the emergence of new keywords such as evacuation planning, risk reduction, risk mitigation, building vulnerability, coastal vulnerability, climate change, probabilistic tsunami hazard assessment (PTVA-3 and PTVA-4). However, topics that were popular in the 2000–2010 period (e.g., paleotsunami deposits, earthquake, and tsunami propagation analysis) also increased in 2011–2023. Conclusions: Research topics with high centrality and density such as seismic hazard will continue to develop and prospect. The cluster network of this topic includes seismoturbidites, sedimentary features, tsunami modeling, active faults, catalog, and historical earthquakes. [ABSTRACT FROM AUTHOR]

Along the French Mediterranean coastlines, most of the studies dealing with tsunamis have focused on hazards, evacuations, or effects of awareness actions, as opposed to hazard perception and knowledge of alert declared locally by the population. To bridge this gap, in this study, data collection yielded 750 responses coming from 150 people living and/or working in the tsunami evacuation zones of five municipalities (e.g., Bandol, Bastia, Cannes, Six-Fours-les-Plages, Sanary-sur-Mer). Early findings confirmed the tendency to underestimate tsunami hazard and a misunderstanding of the alert process. Interestingly, age or location of respondents explained differences between the five surveyed municipalities – more so than gender and residency status. Discrepancies are also observed when we compare the rate of correct answers for similar questions addressed in other areas in the NEAMTWS (North-eastern Atlantic, Mediterranean and connected seas Tsunami Warning System) region, thus confirming local effects. More surprisingly, the respondents who well perceive the tsunami hazard are not those who have a good knowledge of alerts, and the awareness actions do not really impact the tsunami knowledge we evaluated. Also, the results of this study could help local authorities to develop future tsunami awareness actions and to determine more suitable strategies to be applied in the short term at local scales. [ABSTRACT FROM AUTHOR]

This research was conducted to analyze land use change from 2016 to 2022 and their impact on the tsunami hazard zone on the coast of Kebumen Regency. For land use change analysis, remote sensing, geographic information systems (GIS), and statistical tests were applied to Sentinel-2A satellite imagery. The tsunami hazard was simulated using tsunami inundation modeling based on land use spatial data and DEMNAS processed using GIS. Land use changes occurred significantly in the study area, especially in Mirit District. The Southern Cross Road (JJLS) and coastal morphological conditions influence land use change patterns. Land use changes impact changes in the tsunami hazard zone, especially in the use of fir forests and shrimp ponds. The research findings can be used as input for developing a tsunami disaster mitigation plan and detailed spatial planning on the coast of Kebumen Regency. [ABSTRACT FROM AUTHOR]

Greece is located in one of the most seismically active regions in Europe. Many seismic hazard studies have been performed for various sites around Greece, at a regional or local scale. However, the latest national seismic hazard map, currently used for the seismic design of buildings and infrastructure, was published in 2000 and has not been updated since then. In light of recent advances in seismic source and ground motion modeling, the present study focuses on a comparative Probabilistic Seismic Hazard Assessment (PSHA) for the region of East Macedonia and Thrace (EMTH), located in Northern Greece. Various seismic source models are implemented and compared against an updated earthquake catalog to form the necessary source model logic tree. The ground motion logic tree is composed of Ground Motion Prediction Equations (GMPEs), which have been proven suitable for implementation in Greece. PSHA results are presented for the most important cities of East Macedonia and Thrace in a comparative way, which highlights the variability of the seismic hazard among the various seismic source models. An updated seismic hazard map of the study area is proposed, and a comparative disaggregation analysis is performed to estimate the earthquake scenarios with the largest contribution to the seismic hazard. [ABSTRACT FROM AUTHOR]

On 6 February 2023, an M7.8 devastating earthquake started rupturing the East Anatolian fault system in Turkey, resulting in intense shaking that lasted over a minute. A second earthquake of magnitude 7.5 struck near the city of Elbistan a few hours later. Both of these events are associated with the East Anatolian fault system. The earthquake sequence caused widespread damage and collapse of structures in densely populated areas throughout the Southern Turkey and Northern Syria regions and a very large number of human losses. This study focuses on the correlation of the ground deformation with the critical exposure of the infrastructures of Gaziantep and Kahramanmaraş cities. The estimation of the ground deformation of the affected area is achieved with the use of Copernicus Sentinel-2 products and the Normalized Cross Correlation algorithm (NCC) of image matching. The results of the East–West component show that specific sections of the region moved towards the East direction, reaching displacement measurements of 5.4 m, while other sections moved towards the West direction, reaching displacement measurements of 2.8 m. The results of the North–South component show that almost the whole affected area moved towards the North direction, with specific areas reaching displacements of 5.5 m, and a few exemptions, as some areas moved towards the South direction, with displacements reaching even 6.9 m. Regarding the cities of Kahramanmaraş and Gaziantep, their estimated movement direction is North-West and North-East, respectively, and is consistent with the movements of the Arabian and Anatolian Plates in which they are located. Important infrastructures of the study areas (education, museums, libraries, hospitals, monuments, airports, roads and railways) are superimposed on the findings, enabling us to detect the critical exposure rapidly. [ABSTRACT FROM AUTHOR]

Tsunami hazard analysis is an essential step for designing buildings and infrastructure and for safeguarding people and assets in coastal areas. Coastal communities on Vancouver Island are under threat from the Cascadia megathrust earthquakes and tsunamis. Due to the deterministic nature of current megathrust earthquake scenarios, probabilistic tsunami hazard analysis has not been conducted for the coast of Vancouver Island. To address this research gap, this study presents a new probabilistic tsunami hazard model for Vancouver Island from the Cascadia megathrust subduction events. To account for uncertainties of the possible rupture scenarios more comprehensively, time-dependent earthquake occurrence modeling and stochastic rupture modeling are integrated. The time-dependent earthquake model can capture a multi-modal distribution of inter-arrival time data on the Cascadia megathrust events. On the other hand, the stochastic rupture model can consider variable fault geometry, position, and earthquake slip distribution within the subduction zone. The results indicate that the consideration of different inter-arrival time distributions can result in noticeable differences in terms of site-specific tsunami hazard curves and uniform tsunami hazard curves at different return period levels. At present, the use of the one-component renewal model tends to overestimate the tsunami hazard values compared to the three-component Gaussian mixture model. With the increase in the elapsed time since the last event and the duration of tsunami hazard assessment, the differences tend to be smaller. Inspecting the regional variability of the tsunami hazards, specific segments of the Vancouver Island coast are likely to experience higher tsunami hazards due to the directed tsunami waves from the main subduction zone and due to the local underwater topography. [ABSTRACT FROM AUTHOR]

A total of ten tsunami events occurred in Aceh Province from 1991 to 2012. This condition confirms that Aceh Province is very vulnerable to tsunami hazards. In 2004, a tsunami occurred due to the activity of the subduction zone on the west coast of Aceh with a magnitude of Mw 9.3. Since the 2004 tsunami, research on tsunamis has increased. The aim of this study is to reconstruct the 2004 tsunami models, to find out which models are suitable for the events of 2004. There are at least five models of earthquake source faults used for tsunami modeling in this study. The tsunami modeling was carried out numerically using the Tohoku University's Numerical Analysis Model Investigation (TUNAMI) programme. The maximum height obtained from the modeling is 58,05 m at the shoreline. The maximum height obtained from the best model is 17,73 m on land. The M5 fault model produced a tsunami height model that best matches the observation results validated by lowest RMS and highest correlation coefficient values. [ABSTRACT FROM AUTHOR]

In this study, three worst-case credible tsunamigenic scenarios (Mw8.0) from Xiamen fault 1 (XF 1), Xiamen fault 2 (XF 2) and Xiamen fault 3 (XF 3) located off the coast of Xiamen were selected to assess the local tsunami hazard for Xiamen city, Fujian province, China. The GeoClaw model was utilized to compute the propagation and inundation of the tsunami for each scenario. The simulation results show that local tsunamis from XF 1–3 hit Xiamen within 1.5 h of earthquakes. The highest level of tsunami hazard in Xiamen is level II, which corresponds to an inundation depth ranging from 1.2 to 3.0 m. The areas with tsunami hazard level II in each scenario are primarily concentrated in the coastal areas of southern Haicang district and eastern Siming district, which are in the primary propagation direction of the tsunami. Since XF 2 and XF 3 are aligned almost parallel to the coastline of Xiamen, local tsunamis from XF 2 and XF 3 could cause more serious hazards to the coastal areas of Xiamen city. This work provides a typical case for researchers to understand the local tsunami hazard assessment for coastal cities. The research results can provide scientific references for the development of tsunami hazard assessment and early warning systems for coastal cities in southeastern China. [ABSTRACT FROM AUTHOR]

Tides are often the largest source of sea levels fluctuations. Two new probabilistic tsunami hazard assessments (PTHA) methods are proposed to combine the tidal phase uncertainty at the moment of tsunami occurrence with other sources of uncertainty. The first method adopts a Stochastic Reduced Order Model (SROM) producing sets of tidal phase samples to be used in tsunami simulations. The second method uses tsunami simulations with prescribed collocation tidal phases and tide probability distributions to model the uncertainty. The methods are extended to non‐stationary probabilistic tsunami hazard assessment, compounding tsunamis, tides and sea level rise (SLR). As an illustration, these methods are applied for assessing tsunamis generated in the Manila Subduction Zone, on the coasts of Kao Hsiung and Hong Kong. While the SROM‐based method is faster solving for the PTHA if only tides are considered, the collocation‐based method is faster when both SLR and tides are considered. For the illustration case, tides have a relevant impact on PTHA results, however, the SLR within an exposure time of 100 years has stronger impact. PTHA curves of the maximum tsunami elevation are affected by tides and SLR differently. While tides and SLR increase the dispersion of PTHA hazard curve distributions, the latter also produces a translation toward higher elevations. The development of formulations based on SROM or collocation tides is the key to establishing a method which feasibly can be applied to other regions for comprehensive analysis at a global scale. Plain Language Summary: Tsunami hazards can be evaluated using a probabilistic tsunami hazard assessment (PTHA) approach which determines probabilities of exceeding a certain tsunami intensity. A relevant source of uncertainty in PTHA are tides. Tsunamis striking the coast may have different impacts depending on whether they arrive at high or low tide. Moreover, the exposed infrastructure may last many decades and climate‐change‐driven sea‐level‐rise would compound tsunamis and tides, making the hazard worse. We develop two PTHA methods incorporating tides. The first method uses a stochastic reduced order model (SROM). The second method uses sets of tsunami simulations with same tide, known as collocation tidal phases. Both methods aim to estimate tsunami uncertainties and can be also used for non‐stationary probabilistic tsunami hazard assessment which combines tsunamis, tides and sea level rise (SLR). The new methods are applied into an illustration case in South China Sea. The method based on SROM is fastest solving the PTHA with tides. Though, the collocation‐based method is fastest solving for the nPTHA with tides and SLR. While the impact of tides is relevant in PTHA and nPTHA results, SLR produces a greater effect in the studied ports. The conclusions are site‐specific. Key Points: A Stochastic Reduced Order Model (SROM)‐based method and a collocation‐based method incorporating tides and sea level rise (SLR) are evaluated for tsunami hazard assessmentsThe collocation‐based method provides accurate results compared to the SROM‐based methodThe impact of tides and SLR on tsunami intensities depends on the tidal range and SLR within the exposure time, respectively [ABSTRACT FROM AUTHOR]

Earthquake and tsunami predictions comprise huge uncertainties, thus necessitating probabilistic assessments for the design of defense facilities and urban planning. In recent years, computer development has advanced probabilistic tsunami hazard assessments (PTHAs), where hazard curves show the exceedance probability of the maximum tsunami height. However, owing to the lack of historical and geological tsunami records, this method is generally insufficient for validating the estimated hazard curves. The eastern coast of Shikoku in the Nankai subduction zone, Japan, is suitable for validation because tsunami records from historical Nankai Trough earthquakes are available. This study evaluated PTHAs by comparing the tsunami hazard curves and exceedance frequencies of historical Nankai Trough tsunamis. We considered 3480 earthquake scenarios representing the rupture patterns of past Nankai earthquakes and calculated all tsunamis. The probability of earthquake occurrence was based on the Gutenberg–Richter law. We considered uncertainty in tsunami calculations with astronomical tide variations. The estimated tsunami hazard curves are consistent with the exceedance frequencies obtained from historical tsunamis. In addition, sensitivity tests indicate the significance of the earthquake slip heterogeneity and tsunami defense facilities in PTHAs. We also extended the PTHAs to tsunami inundation maps in high resolution and proposed an effective new method for reducing the tsunami computation load. [ABSTRACT FROM AUTHOR]

The Kodiak Islands lie near the southern terminus of the 1964 Great Alaska earthquake rupture area and within the Kodiak subduction zone segment. Both local and trans- Pacific tsunamis were generated during this devastating mega thrust event, but the local tsunami source region and the causative faults are poorly understood. We provide an updated view of the tsunami and earthquake hazard for the Kodiak Islands region through tsunami modeling and geophysical data analysis. Using seismic and bathymetric data, we characterize a regionally extensive seafloor lineament related to the Kodiak shelf fault zone, with focused uplift along a 50-km-long portion of the newly named Ugak fault as the most likely source of the local Kodiak Islands tsunami in 1964. We present evidence of Holocene motion along the Albatross Banks fault zone, but we suggest that this fault did not produce a tsunami in 1964. We relate major structural boundaries to active forearc splay faults, where tectonic uplift is collocated with gravity lineations. Differences in interseismic locking, seismicity rates, and potential field signatures argue for different stress conditions at depth near presumed segment boundaries. We find that the Kodiak segment boundaries have a clear geophysical expression and are linked to upper-plate structure and splay faulting. The tsunamigenic fault hazard is higher for the Kodiak shelf fault zone when compared to the nearby Albatross Banks fault zone, suggesting short wave travel paths and little tsunami warning time for nearby communities. [ABSTRACT FROM AUTHOR]

Offshore Probabilistic Tsunami Hazard Assessments (offshore PTHAs) provide large-scale analyses of earthquake-tsunami frequencies and uncertainties in the deep ocean, but do not provide high-resolution onshore tsunami hazard information as required for many risk-management applications. To understand the implications of an offshore PTHA for the onshore hazard at any site, in principle the tsunami inundation should be simulated locally for every earthquake scenario in the offshore PTHA. In practice this is rarely feasible due to the computational expense of inundation models, and the large number of scenarios in offshore PTHAs. Monte Carlo methods offer a practical and rigorous alternative for approximating the onshore hazard, using a random subset of scenarios. The resulting Monte Carlo errors can be quantified and controlled, enabling high-resolution onshore PTHAs to be implemented at a fraction of the computational cost. This study develops efficient Monte Carlo approaches for offshore-to-onshore PTHA. Modelled offshore PTHA wave heights are used to preferentially sample scenarios that have large offshore waves near an onshore site of interest. By appropriately weighting the scenarios, the Monte Carlo errors are reduced without introducing bias. The techniques are demonstrated in a high-resolution onshore PTHA for the island of Tongatapu in Tonga, using the 2018 Australian PTHA as the offshore PTHA, while considering only thrust earthquake sources on the Kermadec-Tonga trench. The efficiency improvements are equivalent to using 4–18 times more random scenarios, as compared with stratified-sampling by magnitude, which is commonly used for onshore PTHA. The greatest efficiency improvements are for rare, large tsunamis, and for calculations that represent epistemic uncertainties in the tsunami hazard. To facilitate the control of Monte Carlo errors in practical applications, this study also provides analytical techniques for estimating the errors both before and after inundation simulations are conducted. Before inundation simulation, this enables a proposed Monte Carlo sampling scheme to be checked, and potentially improved, at minimal computational cost. After inundation simulation, it enables the remaining Monte Carlo errors to be quantified at onshore sites, without additional inundation simulations. In combination these techniques enable offshore PTHAs to be rigorously transformed into onshore PTHAs, with quantification of epistemic uncertainties, while controlling Monte Carlo errors. [ABSTRACT FROM AUTHOR]

The current diffuse-strain model of the collision between Africa and Eurasia in the western Mediterranean predicts a broad region with deformation distributed among numerous faults and moderate-magnitude seismicity. However, the model is untested because most deformation occurs underwater, at poorly characterized faults of undetermined slip. Here we assess the diffuse-strain model analysing two active offshore fault systems associated with the most prominent seafloor relief in the region. We use pre-stack depth migrated seismic images to estimate, for the first time, the total Plio-Holocene slip of the right-lateral Yusuf and reverse Alboran Ridge structurally linked fault system. We show that kinematic restoration of deformational structures predicts a slip of 16 ± 4.7 km for the Alboran Ridge Fault and a minimum of 12 km for the Yusuf Fault. Thus, this fault system forms a well-defined narrow plate boundary that has absorbed most of the 24 ± 5 km Plio-Holocene Africa-Eurasia convergence and represents an underappreciated hazard. Conventional models propose multiple fault systems across a diffuse deformation zone absorbing plate convergence in the western Mediterranean. Here the authors show new data supporting the active development of a single plate boundary fault system, representing an underappreciated seismic and tsunami hazard. [ABSTRACT FROM AUTHOR]

Coastal areas of Indonesia that are close to tectonic plates are vulnerable to earthquakes and generated tsunamis. The Munjungan Coast South of East Java-Indonesia is such a vulnerable tsunami area. This coastal area, besides being close to tectonic plate boundaries, has the shape of an open bay which makes it particularly vulnerable to tsunami impacts and, therefore, in need of strict disaster mitigation measures. Assisted Geographic Information System (GIS) applications with map overlay techniques and by the Arc View 3.3 software program can help in the taking of measures that can reduce the impact of tsunami hazards. The processed product of the GIS methodology in the form of a tsunami hazard zoning map, as well as designated evacuation route maps, can be helpful tools in tsunami impact mitigation, when a significant and potentially tsunamigenic earthquake occurs. The present study used a survey method and area sampling to obtain a better understanding of the public’s perceptions and attitudes in responding more effectively to the potential of tsunami disasters. Based on the interpretation of the zoning map for the classification of disasterprone areas and route maps for evacuation, four villages were identified as being more prone to tsunami disasters. The condition of the population in these four disaster-prone villages, despite their higher level of knowledge about tsunamis, was not followed by their perceptions and proper attitudes towards mitigating the potential danger. People on the coast of Munjungan did not appear to be particularly concerned about the tsunami hazard. [ABSTRACT FROM AUTHOR]

The potential of a full-margin rupture along the Cascadia subduction zone poses a significant threat over a populous region of North America. Previous probabilistic tsunami hazard assessment studies produced hazard curves based on simulated predictions of tsunami waves, either at low resolution or at high resolution for a local area or under limited ranges of scenarios or at a high computational cost to generate hundreds of scenarios at high resolution. We use the graphics processing unit (GPU)-accelerated tsunami simulator VOLNA-OP2 with a detailed representation of topographic and bathymetric features. We replace the simulator by a Gaussian process emulator at each output location to overcome the large computational burden. The emulators are statistical approximations of the simulator's behaviour. We train the emulators on a set of input–output pairs and use them to generate approximate output values over a six-dimensional scenario parameter space, e.g. uplift/subsidence ratio and maximum uplift, that represent the seabed deformation. We implement an advanced sequential design algorithm for the optimal selection of only 60 simulations. The low cost of emulation provides for additional flexibility in the shape of the deformation, which we illustrate here considering two families – buried rupture and splay-faulting – of 2000 potential scenarios. This approach allows for the first emulation-accelerated computation of probabilistic tsunami hazard in the region of the city of Victoria, British Columbia. [ABSTRACT FROM AUTHOR]

Unmanned Aerial Vehicles (UAV) are widely used in disaster relief and road exploration in recent years. This paper mainly studied the emergency response of UAVs after disasters. The UAV response system is mainly suitable for the distribution of necessities and road exploration after geological disasters and tsunamis in coastal areas. By analyzing the problem and making reasonable assumptions, the optimization model was established with the traffic planning theory, and MATLAB software was used to program and solve the problem. An optimal scheduling scheme was presented to solve these problems. The normalization method was used to select a highly capable UAV. Taking the minimum volume of idle space buffer material as the objective function and taking into account the constraints, such as payload of unmanned aerial vehicle, a single objective programming model was established. The results are as follows: Each International Standards Organization (ISO) cargo container has five UAVs B, one UAV C, one UAV F and one UAV H. It provides 188 days of relief requirements with ISO cargo containers' space utilization of 71.4%. The research shows that the UAV response system has the functions of necessities distribution and road exploration after disasters, and can be used to deal with the emergency response after disasters in coastal areas, and has a wide range of applicability. [ABSTRACT FROM AUTHOR]

We face a new era in the assessment of multiple natural hazards whose statistics are becoming alarmingly non‐stationary due to ubiquitous long‐term changes in climate. One particular case is tsunami hazard affected by climate‐change‐driven sea level rise (SLR). A traditional tsunami hazard assessment approach where SLR is omitted or included as a constant sea‐level offset in a probabilistic calculation may misrepresent the impacts of climate‐change. In this paper, a general method called non‐stationary probabilistic tsunami hazard assessment (nPTHA), is developed to include the long‐term time‐varying changes in mean sea level. The nPTHA is based on a non‐stationary Poisson process model, which takes advantage of the independence of arrivals within non‐overlapping time‐intervals to specify a temporally varying hazard mean recurrence rate, affected by SLR. The nPTHA is applied to the South China Sea (SCS) for tsunamis generated by earthquakes in the Manila Subduction Zone. The method provides unique and comprehensive results for inundation hazard, combining tsunami and SLR at a specific location over a given exposure time. The results show that in the SCS, SLR has a significant impact when its amplitude is comparable to that of tsunamis with moderate probability of exceedance. The SLR and its associated uncertainty produce an impact on nPTHA results comparable to that caused by the uncertainty in the earthquake recurrence model. These findings are site‐specific and must be analyzed for different regions. The proposed methodology, however, is sufficiently general to include other non‐stationary phenomena and can be exploited for other hazards affected by SLR. Plain Language Summary: Assessing natural hazards that are made worse by climate change cannot use previous methods that assume that the average behavior is a good representation of the hazard. Here we show the effect of climate‐change‐driven sea level rise (SLR) on tsunami hazard, where the continuously increasing SLR cannot be represented by an average value. Higher sea levels produce several changes in the tsunami behavior, including an increase in the maximum tsunami water level and in the speed the tsunami propagates. We introduce a new method which incorporates the long‐term time‐varying changes in mean sea level. The method can be applied to other coastal hazards, such as storm surge and waves. The new method is applied to port cities in the South China Sea (SCS) for tsunamis generated by earthquakes in the Manila Subduction Zone. We determine the probability of flooding urban areas within 50 and 100 years. The hazard in SCS is significantly impacted by SLR when it rises by an amount comparable to the tsunami height for a tsunami with moderate likelihood. The effect is comparable to that caused by the estimated uncertainty in recurrence interval of the causative earthquake. These results, though, are site‐specific. Key Points: The impact of sea level rise (SLR) on probabilistic tsunami hazard assessment (PTHA) depends on the exposure time and the relative magnitude of both phenomenaFor the probabilistic tsunami hazard assessment (PTHA) in South China Sea, the sea level rise (SLR) is as important as the uncertainty of the earthquake recurrence modelSea level rise (SLR) can change the tsunami propagation properties so probabilistic tsunami hazard assessment (PTHA) must include nonlinear effects in the tsunami behavior and inundation level [ABSTRACT FROM AUTHOR]

Eastern Indonesia is one of the world's most complex regions in terms of tsunami hazards, as it accommodates numerous seismic and non-seismic tsunami sources with a history of deadly tsunamis. This study is an effort to enhance tsunami hazard knowledge in eastern Indonesia where limited data and analyses exist. We provide a brief understanding of eastern Indonesia's tsunami hazards by modelling selected deterministic tsunami scenarios from tectonic, submarine mass failure (SMF), and volcanic sources. To our knowledge, this is the first time that tsunami hazards modelling from such diverse sources in Indonesia has been performed. Our methodology is a deterministic tsunami hazard analysis considering credible tsunami sources from historical and contemporary data, modelling them using state-of-the-art simulation tools. We modelled two Mw7.8 tsunamigenic earthquake scenarios on the Flores back-arc thrust, one rupturing the basal fault (FBT-BF) and the other rupturing the splay fault (FBT-SF), showing that the two scenarios produce maximum tsunami amplitudes of ∼ 5.3 m and ∼ 4.2 m, respectively, which are comparable to the deadly 1992 Flores tsunami. We modelled potential SMF-generated tsunamis in the Makassar Strait with SMF volumes of 5 km 3 and 225 km 3 which yielded maximum tsunami heights of ∼ 1.1 m and ∼ 4.3 m along the eastern coast of Kalimantan Island and ∼ 2.9 m and ∼ 11.1 m along the west shore of Sulawesi Island, respectively. The 1871 Ruang volcanic tsunami is studied through existing historical documents and a source model is proposed comprising a flank collapse with volume of 0.10 km 3 . Such a source model successfully reproduced the 25 m runup reported in a historical account. [ABSTRACT FROM AUTHOR]

On the 5th of December 2018, a magnitude Mw 7.5 earthquake occurred southeast of Maré, an island of the Loyalty Archipelago, New Caledonia. This earthquake is located at the junction between the plunging Loyalty ridge and the southernmost Vanuatu arc, in a tectonically very active area regularly subjected to strong seismic crises and events higher than magnitude 7 and up to 8. Widely felt in New Caledonia it has been immediately followed by a tsunami warning, confirmed shortly after by a first wave arrival at the Loyalty Islands tide gauges (Maré and Lifou), then along the east coast of Grande Terre of New Caledonia and in several islands of the Vanuatu Archipelago. Seafloor initial deformation linked to tsunami generation has been modeled with MOST numerical code using earthquake parameters available from seismic observatories. Then the wave propagation has been modeled using SCHISM, another modelling code solving the shallow water equations on an unstructured grid based on a new regional DEM of ~180 m resolution and allowing refinement in many critical areas. Finally, the results have been compared to tide gauge records, field observations and testimonials from 2018. The arrival times, wave amplitude and polarities present good similarities, especially in far-field locations (Hienghène, Port-Vila and Poindimié). Maximum wave heights and energy maps for two different scenarios highlight the fact that the orientation of the source (strike of the rupture) played an important role, focusing the maximum energy path of the tsunami south of Grande-Terre and the Isle of Pines. However, both scenarios indicate similar propagation toward Aneityum, Vanuatu southernmost island, the bathymetry acting like a waveguide. This study has a significant implication in tsunami hazard mitigation in New Caledonia as it helps to validate the modelling code and process used to prepare a scenarios database for warning and coastal evacuation. [ABSTRACT FROM AUTHOR]

We propose the use of variable resolution boundaries based on Central Voronoi Tessellations (CVT) to spatially aggregate building exposure models for risk assessment to various natural hazards. Such a framework is especially beneficial when the spatial distribution of the considered hazards present intensity measures with contrasting footprints and spatial correlations such as in coastal environments. This proposal avoids the incorrect assumption that a single intensity value from hazards with low spatial correlation (e.g. tsunami) are considered as representative within large sized geocells for physical vulnerability assessment, without, at the same time, increasing the complexity of the overall model. We present decoupled earthquake and tsunami scenario-based risk estimates for the residential building stock of Lima (Peru). We observe that earthquake loss models for far-field subduction sources are practically insensitive to the exposure resolution. Conversely, tsunami loss models and associated uncertainties depend on the spatial correlations of the hazard intensities as well as on the resolution of the exposure models. We observe that for the portfolio located in the coastal area exposed to both perils in Lima, the ground-shaking dominates the losses for lower magnitudes whilst the tsunami does for the larger ones. For the latter, two sets of existing empirical flow-depth fragility models are used, finding large differences in the losses. This study arises awareness about the uncertainties in the selection of fragility models and aggregations entities for exposure modelling and loss mapping. [ABSTRACT FROM AUTHOR]

The final aim of the present work is to propose a NTHMP-benchmarked numerical tool for landslide-generated tsunami hazard assessment. To achieve this, the novel Multilayer-HySEA model is validated using laboratory experiment data for landslide-generated tsunamis. In particular, this second part of the work deals with granular slides, while the first part, in a companion paper, considers rigid slides. The experimental data used have been proposed by the US National Tsunami Hazard and Mitigation Program (NTHMP) and were established for the NTHMP Landslide Benchmark Workshop, held in January 2017 at Galveston (Texas). Three of the seven benchmark problems proposed in that workshop dealt with tsunamis generated by rigid slides and are collected in the companion paper. Another three benchmarks considered tsunamis generated by granular slides. They are the subject of the present study. The seventh benchmark problem proposed the field case of Port Valdez, Alaska, 1964 and can be found in. In order to reproduce the laboratory experiments dealing with granular slides, two models need to be coupled: one for the granular slide and a second one for the water dynamics. The coupled model used consists of a new and efficient hybrid finite-volume–finite-difference implementation on GPU architectures of a non-hydrostatic multilayer model coupled with a Savage–Hutter model. To introduce the multilayer model more fluidly, we first present the equations of the one-layer model, Landslide-HySEA, with both strong and weak couplings between the fluid layer and the granular slide. Then, a brief description of the multilayer model equations and the numerical scheme used is included. The dispersive properties of the multilayer model can be found in the companion paper. Then, results for the three NTHMP benchmark problems dealing with tsunamis generated by granular slides are presented with a description of each benchmark problem. [ABSTRACT FROM AUTHOR]

This paper is devoted to benchmarking the Multilayer-HySEA model using laboratory experimental data for landslide-generated tsunamis. This article deals with rigid slides, and the second part, in a companion paper, addresses granular slides. The US National Tsunami Hazard and Mitigation Program (NTHMP) has proposed the experimental data used and established for the NTHMP Landslide Benchmark Workshop, held in January 2017 at Galveston (Texas). The first three benchmark problems proposed in this workshop deal with rigid slides. Rigid slides must be simulated as a moving bottom topography, and, therefore, they must be modeled as a prescribed boundary condition. These three benchmarks are used here to validate the Multilayer-HySEA model. This new HySEA model consists of an efficient hybrid finite-volume–finite-difference implementation on GPU architectures of a non-hydrostatic multilayer model. A brief description of model equations, dispersive properties, and the numerical scheme is included. The benchmarks are described and the numerical results compared against the lab-measured data for each of them. The specific aim is to validate this new code for tsunamis generated by rigid slides. Nevertheless, the overall objective of the current benchmarking effort is to produce a ready-to-use numerical tool for real-world landslide-generated tsunami hazard assessment. This tool has already been used to reproduce the Port Valdez, Alaska, 1964 and Stromboli, Italy, 2002 events. [ABSTRACT FROM AUTHOR]

In November 2013, Super Typhoon Haiyan (Yolanda) hit the Philippines. It caused heavy loss of lives and extensive damages to buildings and infrastructure. When collapsed buildings are focused on, it is interesting to find that these buildings did not collapse for the same reasons after the landfall of the typhoon and storm surge. The objective of this study is to develop a statistical model for building damage due to Super Typhoon Haiyan and its storm surge. The data were collected in collaboration with Tanauan Municipality, the Philippines. The data for the inundation map were obtained by field surveys conducted on-site to determine the cause of the damages inferred from satellite data. The maximum wind speed was derived from the Holland parametric hurricane model based on the Japan Meteorological Agency (JMA) typhoon track data and the inundation depth of storm surge was calculated using the MIKE model. Multinomial logistic regression was used to develop a model to identify the significant factors influencing the damage to buildings. The result of this work is expected to be used to prepare urban plans for preventing damage from future storms. [ABSTRACT FROM AUTHOR]

The present work aims to ascertain the deterministic tsunami hazard map for maximum wave height along the Indian coastline due to subduction events in the Sumatra region. The region between 15°S-30°N lat. and 50°E-115°N long. was modelled in using Geoclaw, which discretizes and solves the shallow-water wave equation using adaptive finite volume algorithm. The developed model was suitably validated for the available tidal gauge and altimeter data for the 2004 Mw 9.12 Sumatra earthquake with input source characteristics from the SRCMOD data. Further, a sensitivity study based on slip variability and location was conducted which revealed that near-field stations were highly sensitive at all locations while far-field stations were more sensitive towards source locations. Furthermore, 25 non-Gaussian slip fields were generated for the maximum possible event (Mw 9.12) for the region and placed suitably along the active Sumatra subduction region. Then the wave heights from all the simulations were assembled to determine the deterministic tsunami hazard values with respect to maximum wave heights for the coastal regions of India and adjoining regions. The results will find application in the design of structures along the coastline of the study region. [ABSTRACT FROM AUTHOR]

Nankai–Tonankai megathrust earthquakes and tsunamis pose significant risks to coastal communities in western and central Japan. Historically, this seismic region hosted many major earthquakes, and the current national tsunami hazard assessments in Japan consider megathrust events as those having moment magnitudes between 9.0 and 9.1. In responding to the lack of rigorous uncertainty analysis, this study presents an extensive tsunami hazard assessment for the Nankai–Tonankai Trough events, focusing on the southwestern Pacific region of Japan. A set of 1000 kinematic earthquake rupture models is generated via stochastic source modelling approaches, and Monte Carlo tsunami simulations are carried out by considering high-resolution grid data of 10 m and coastal defence structures. Significant advantages of the stochastic tsunami simulation methods include the enhanced capabilities to quantify the uncertainty associated with tsunami hazard assessments and to effectively visualize the results in an integrated manner. The results from the stochastic tsunami simulations can inform regional and local tsunami risk reduction actions in light of inevitable uncertainty associated with such tsunami hazard assessments and complement conventional deterministic tsunami scenarios and their hazard predictions, such as those developed by the Central Disaster Management Council of the Japanese Cabinet Office. [ABSTRACT FROM AUTHOR]

The article addresses the application of non-classical operational calculus to approximative solutions of engineering problems. The engineering-sound examples show that a continuous–discrete problem transformation from differential unequivocal problem to a differential wildcard problem, triggering a change in solution quality. A number of approximative methods are capable to alter both quantitative and qualitative solution effects. [ABSTRACT FROM AUTHOR]

The present work is devoted to the benchmarking of the Multilayer-HySEA model using laboratory experiment data for landslide generated tsunamis. This first part of the work deals with rigid slides and the second part, in a companion paper, with granular slides. The US National Tsunami Hazard and Mitigation Program (NTHMP) has proposed the experimental data used and established for the NTHMP Landslide Benchmark Workshop, held in January 2017 at Galveston. The first three benchmark problems proposed in this workshop dealt with rigid slides, simulated as a moving bottom topography, that must be imposed as a prescribed boundary condition. These three benchmarks are used here to validate the Multilayer-HySEA model. This new model of the HySEA family consists of an efficient hybrid finite volume/finite difference implementation on GPU architectures of a non-hydrostatic multilayer model. A brief description of model equations, its dispersive properties, and the numerical scheme is included. The benchmarks are described and the numerical results compared against the lab measured data for each of them. The specific aim of the present work is to validate this new code for tsunamis generated by rigid slides. Nevertheless, the overall objective of the current benchmarking effort is to produce a ready-to-use numerical tool for real world landslide generated tsunami hazard assessment. This tool has already been used to reproduce the Port Valdez Alaska 1969 event. [ABSTRACT FROM AUTHOR]

Tsunamis induced by the landslide will divide into a traveling wave component propagating along the coastline and an offshore wave component propagating perpendicular to the coastline. The offshore tsunami wave has the non-negligible energy and destruction in enclosed basins as fjords, reservoirs, and lakes, which are worth studying. The initial submergence condition, the falling height and sliding angle of slider, are important reference indexes of damage degree of landslide and may also matter at that of the landslide-induced tsunami. Depending on the fully coupled model, the effects of them on the production and propagation of the tsunami were considered in the study. Since the slider used was semi-elliptic, the effect of the ratio of the long axis to the short axis was also analyzed. According to the computational fluid dynamics theory, a numerical wave tank was developed by the immersed boundary (IB) method; besides, the general moving-object module of slide mass was also embedded to the numerical tanker. The results indicate that the effects of the squeezing and pushing of the slider on water produce a naturally attenuated wave at the front of the wave train, and the attenuation becomes more serious with the increase in the initial submersion range of the slider. The effects of the vertical movement of the slider cause the increase in the amplitude of the back of the wave train. As the falling height increases, the large wave height increases when the slider is initially submerged and decreases when it is not initially submerged, except for the accidental elevation of that at smaller falling heights. The results also indicate that the hazard of the subaerial landslide-induced tsunami is greater under a small or large falling angle, and that of the partial subaerial and submarine landslide-induced tsunami is greater under a small falling angle. With the increase in the ratio of the long axis to the short axis, the total induced wave energy decreases and the shape of the wave train proportionally reduces, while the wave propagation mode does not change. [ABSTRACT FROM AUTHOR]

The December 2004 Sumatra-Andaman tsunami prompted an unprecedented research effort to find ancient precursors and quantify the recurrence time of such a deadly natural disaster. This effort, however, has focused primarily along the northern and eastern Indian Ocean coastlines, in proximal areas hardest hit by the tsunami. No studies have been made to quantify the recurrence of tsunamis along the coastlines of the western Indian Ocean, leading to an underestimation of the tsunami risk in East Africa. Here, we document a 1000-yr- old sand layer hosting archaeological remains of an ancient coastal Swahili settlement in Tanzania. The sedimentary facies, grain-size distribution, and faunal assemblages indicate a tsunami wave as the most likely cause for the deposition of this sand layer. The tsunami in Tanzania is coeval with analogous deposits discovered at eastern Indian Ocean coastal sites. Numerical simulations of tsunami wave propagation indicate a megathrust earthquake generated by a large rupture of the Sumatra-Andaman subduction zone as the likely tsunami source. Our findings provide evidence that teletsunamis represent a serious threat to coastal societies along the western Indian Ocean, with implications for future tsunami hazard and risk assessments in East Africa. [ABSTRACT FROM AUTHOR]

Motivated by the unwarned tsunami disaster caused by the flank collapse of the Anak Krakatau volcano on 22 December 2018, we used a landslide tsunami model to explore potential tsunami observing and warning systems for the region. With the estimated volume of 0.24 km3 and the relatively short duration (~3 to 5 min), the landslide of the volcanic edifice in the southwest sector triggered a tsunami of higher than 40 m in the vicinity. The tsunami, however, attenuated rapidly as it propagated away from the generation area, resulting in lower than 2 m wave heights at tide gauges around the Sunda Strait. Using the tsunami model, we demonstrated the capability of a ship height positioning method to detect the tsunami of amplitude ~20 cm associated with the event. Furthermore, assimilating the tsunami current velocity observed by high‐frequency oceanographic radars can produce accurate forecasts of coastal tsunami heights. Plain Language Summary: The tsunami on 22 December 2018 claimed hundreds of lives across the Sunda Strait regions of Indonesia. Unlike typical tsunamis, this silent tsunami was caused by the activity of Anak Krakatau volcano. This paper proposes new tsunami observation and warning systems for such a tsunami by modeling the generation and propagation processes. Although the source characteristics are constrained using limited data, that is, satellite images, the model can reproduce tsunami waveforms recorded at tide gauges and flow depths measured at specified regions. We then perform numerical experiments to assess the performance of potential tsunami observing systems based on high‐frequency oceanographic radars and ship‐height positioning. The experiment suggests that both systems can be viable future tsunami observations in the region. Key Points: The study models the tsunami generation and propagation processes associated with the Anak Krakatau volcanoWe validate our model against tsunami waveforms at tide gauges and flow depthsBased on the model, tsunami observing systems using oceanographic radars and ship height positioning are suitable for the region [ABSTRACT FROM AUTHOR]

Climate change currently affects the resilience and aquatic ecosystem. Climate change alters rainfall patterns which have a great impact on river flow. Annual flooding is an important hydrological characteristic of the Mekong River Basin (MRB) and it drives the high productivity of the ecosystem and biodiversity in the Tonle Sap floodplain and the Mekong Delta. This study aims to assess the impacts of climate change on river flow in the MRB and flood inundation in the Lower Mekong Basin (LMB). The changing impacts were assessed by a two-dimensional rainfall-runoff and inundation model (RRI model). The present climate (1979–2003) and future projected climate (2075–2099) datasets from MRI-AGCM3.2H and MRI-AGCM3.2S models were applied with a linear scaling bias correction method before input into the RRI model. The results of climate change suggested that flood magnitude in the LMB will be severer than the present climate by the end of the twenty-first century. The increment of precipitation between 6.6 and 14.2% could lead to increase extreme flow (Q5) 13–30%, peak inundation area 19–43%, and peak inundation volume 24–55% in the LMB for ranging of Representative Concentration Pathways (RCP) and sea surface temperature (SST) scenarios while there is no significant change on peak flood timing. [ABSTRACT FROM AUTHOR]

Frictional properties on subduction interfaces are essential for understanding earthquake nucleation, rupture propagation, and tsunami generation during megathrust earthquakes. Because they cannot be directly observed, they have been inferred from different approaches. However, none of them have reported constraints immediately before a megathrust earthquake. Here we quantify the frictional strength on the megathrust prior to the 2012 Mw 7.6 Nicoya earthquake by conducting spontaneous rupture simulations with constraints from near‐field observations. Our preferred dynamic rupture model shows a remarkable fit on the near‐field data. The simulation results indicate an average strength drop of <5 MPa. Considering typical ranges for the dynamic friction coefficient fd ≤ 0.2 and the static friction coefficient fs = 0.6, we infer that the average strength on the megathrust is ≤7.5 MPa. Such low strength is attributed to the near‐lithostatic pore pressure along the subduction interface, which is implied by seismic studies in this region. Plain Language Summary: Subduction zones host a preponderance of great earthquakes that are sometimes accompanied by destructive tsunamis. The frictional resistance (strength) on subduction interfaces, termed megathrusts, plays critical roles in controlling earthquake rupture process and thus significantly impacts the ground motion intensity and the tsunamigenic potential during earthquakes. However, the strength on the megathrust is difficult to estimate directly and evolves over time. Here, we constrain the strength on the Nicoya megathrust shortly before the 2012 Nicoya Mw 7.6 earthquake with constraints from near‐field observations. Based on the simulation results, we infer the strength on the megathrust prior to the earthquake to be less than 7.5 MPa. Such low strength at ~25 km in depth indicates the existence of compacted fluids with a high pore pressure. Key Points: We resolve the dynamic rupture process of the 2012 Nicoya Mw 7.6 earthquake with constraints from near‐field observationsThe preferred dynamic rupture model shows remarkable fit on near‐field displacements and velocity waveformsStrength on Nicoya megathrust prior to the earthquake is inferred to be very low (~7.5 MPa), indicating the near‐lithostatic pore pressure [ABSTRACT FROM AUTHOR]

The effects of the unpredictability of the flow system in a karst area, with respect to bacterial communities in the aquatic environment, were evaluated. Bacterial communities from two different types of flow conditions (spring and sinkhole) were characterized and compared in the karst area. Proteobacteria, Bacteroidetes, and Verrucomicrobia were the major phyla present in the sampled spring and sinkhole waters. The water samples from the spring points were heavily loaded with Actinobacteria, especially Firmicutes, which accounted for 4.3% of the bacterial content. Furthermore, Actinobacteria were prevalent in some water samples, serving as indicators of the effects of seawater inundation. The richness and diversity of bacterial species were evaluated at the spring and sinkhole water points. The spring waters showed a higher bacterial richness and diversity compared to the sinkhole waters. Our results provide valuable information for the evaluation and investigation of microbial compositions in karst areas, which are characterized by heterogeneous hydrological conditions. The microbial species in karst areas are already exposed to changing hydrogeological conditions, and are likely to be confronted with future changes; thus, their spatiotemporal variations reflect the shifting baselines of physicochemical and ecosystem processes. [ABSTRACT FROM AUTHOR]

This paper presents a Bayesian network model to assess the vulnerability of the flood control infrastructure and to simulate failure cascade based on the topological structure of flood control networks along with hydrological information gathered from sensors. Two measures are proposed to characterize the flood control network vulnerability and failure cascade: (a) node failure probability (NFP), which determines the failure likelihood of each network component under each scenario of rainfall event, and (b) failure cascade susceptibility, which captures the susceptibility of a network component to failure due to failure of other links. The proposed model was tested in both single watershed and multiple watershed scenarios in Harris County, Texas using historical data from three different flooding events, including Hurricane Harvey in 2017. The proposed model was able to identify the most vulnerable flood control network segments prone to flooding in the face of extreme rainfall. The framework and results furnish a new tool and insights to help decision‐makers to prioritize infrastructure enhancement investments and actions. The proposed Bayesian network modeling framework also enables simulation of failure cascades in flood control infrastructures, and thus could be used for scenario planning as well as near‐real‐time inundation forecasting to inform emergency response planning and operation, and hence improve the flood resilience of urban areas. [ABSTRACT FROM AUTHOR]

The eruption of Anak Krakatoa Volcano is assumed to be the cause to generate tsunami wave; it can also be assumed that the wave source is only about 50.3 km from the coast. The interesting point is that the propagation of the tsunami wave was not caused by an earthquake but rather by volcanic material from Anak Krakatoa Volcano which slid into the sea. An investigation was conducted using spatial analysis of coastal areas around Tanjung Lesung, Banten with GIS analysis. While the propagation of tsunami waves was calculated from Anak Krakatoa Volcano that was projected towards Tanjung Lesung, Banten. These analyses were done to obtain assumptions of the wave velocity and propagation time from the center of the wave to the coastal area. The primary purpose of this study is to investigate the effectiveness of the vegetation belts as tsunami mitigation. This study used a 2D numerical simulation wave based on a VOF method. The numerical simulation calculated the interaction between the bore wave propagation and the vegetation belts. Numerical analysis was done to estimate the altitude and velocity of tsunami waves toward the coastal area of Tanjung Lesung. By comparing the results of the spatial and numerical analysis, the delineation of the tsunami-affected area on 31 December 2018 can be determined. [ABSTRACT FROM AUTHOR]

Floods often occur in Lubuk Buaya residential housing in Padang city, which has a population of 6,500 citizens per km2. These natural phenomena happen due to sea level water rises and the change in the new river mouth of the Batang Kandis river. The construction of a 500 m floodway and a 700 m dike of Batang Kandis river were proposed to control flooding. The floodway was then damaged during the earthquake on September 30th, 2009, and wiped out by a flood on March 24th, 2016. Theoretically, to solve flood conditions downstream of Batang Kandis river with 70 km2 of watershed area, the floodway is expected to be able to discharge 307 m3/s. This study uses a numerical simulation using HEC-RAS software with three scenarios. The first scenario uses the existing condition of the river width of 50 m and a depth of 1 m, it experienced an inundated area of 0.60 km2 for 5 hours. The second scenario is done by increasing 2.50 m embankment height, which gave the result of 2x700 m2 flood inundation in several locations. The third scenario also carried out dredging of the river up to the elevation of 0.00 m above sea level, and there was no flood inundation. Thus, the third scenario is the best result that has been carried out to control the floods downstream of Batang Kandis river. [ABSTRACT FROM AUTHOR]

Submarine landslides that occur offshore are common along the U.S. continental margins. These mass wasting events can trigger tsunamis and hence potentially devastate coastal communities and damage offshore infrastructure. However, the initiation and failure processes of submarine landslides are poorly understood. Here, we identify and locate 85 previously unknown submarine landslides in the Gulf of Mexico from 2008 to 2015. Ten of these landslides failed spontaneously while the remaining 75 were dynamically triggered by passing seismic surface waves from distant earthquakes with magnitudes as small as ∼5. Our observations demonstrate ongoing submarine landslide activity in the Gulf of Mexico where dense energy industry infrastructure is present and that the region is prone to secondary seismic hazard despite the low local seismicity rate. Our results should facilitate future investigations to identify unstable offshore slopes, to illuminate dynamic processes of landslides, and perhaps to apply remote detection technology in tsunami warning systems. Plain Language Summary: Landslides under the ocean are termed submarine landslides. Submarine landslides can pose hazards to coastal communities and offshore infrastructure, including triggering tsunamis and damaging oil platforms, pipelines, and submarine cables. These devastations may further cause environmental damages such as oil spills. Identifying these landslides and understanding their failure processes have both societal significance and intellectual merit. Using 8 years of continuous seismic data, we found 85 previously unknown submarine landslides in the Gulf of Mexico from 2008 to 2015. Ten of these landslides occurred without preceding earthquakes while the remaining 75 were triggered by the passing seismic surface waves from distant earthquakes. Our approach suggests that a remote detection technology for offshore landslides could be applied in tsunami warning systems. Key Points: Abundant submarine landslides were observed in the Gulf of MexicoMany of the landslides were dynamically triggered by remote earthquakesThere is no clear magnitude dependence of the triggering earthquakes [ABSTRACT FROM AUTHOR]

The Indian Tsunami Early Warning System (ITEWS) was established at the Indian National Centre for Ocean Information Services, Hyderabad in October 2007 following the devastating tsunami on 26 December 2004. The Intergovernmental Oceanographic Commission of United Nations Educational, Scientific and Cultural Organization (IOC/UNESCO) coordinated with the National Tsunami Warning Centers in the Indian Ocean region and promoted the establishment of a well-knit tsunami early warning system called Indian Ocean Tsunami Warning and Mitigation System (IOTWMS) so that all countries on the Indian Ocean can get benefitted. The end-to-end capabilities of this warning system have been well-proven during the tsunamigenic earthquakes that occurred since September 2007. The capability of the system is examined, with special reference to Indian Tsunami Early Warning System (ITEWS), to ascertain the readiness of the Indian Ocean region to face a major tsunami. [ABSTRACT FROM AUTHOR]