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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.

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]

Probabilistic Tsunami Hazard Analysis (PTHA) quantifies the probability of exceeding a specified inundation intensity at a given location within a given time interval. PTHA provides scientific guidance for tsunami risk analysis and risk management, including coastal planning and early warning. Explicit computation of site-specific PTHA, with an adequate discretization of source scenarios combined with high-resolution numerical inundation modelling, has been out of reach with existing models and computing capabilities, with tens to hundreds of thousands of moderately intensive numerical simulations being required for exhaustive uncertainty quantification. In recent years, more efficient GPU-based High-Performance Computing (HPC) facilities, together with efficient GPU-optimized shallow water type models for simulating tsunami inundation, have now made local long-term hazard assessment feasible. A workflow has been developed with three main stages: 1) Site-specific source selection and discretization, 2) Efficient numerical inundation simulation for each scenario using the GPU-based Tsunami-HySEA numerical tsunami propagation and inundation model using a system of nested topo-bathymetric grids, and 3) Hazard aggregation. We apply this site-specific PTHA workflow here to Catania, Sicily, for tsunamigenic earthquake sources in the Mediterranean. We illustrate the workflows of the PTHA as implemented for High-Performance Computing applications, including preliminary simulations carried out on intermediate scale GPU clusters. We show how the local hazard analysis conducted here produces a more fine-grained assessment than is possible with a regional assessment. However, the new local PTHA indicates somewhat lower probabilities of exceedance for higher maximum inundation heights than the available regional PTHA. The local hazard analysis takes into account small-scale tsunami inundation features and non-linearity which the regional-scale assessment does not incorporate. However, the deterministic inundation simulations neglect some uncertainties stemming from the simplified source treatment and tsunami modelling that are embedded in the regional stochastic approach to inundation height estimation. Further research is needed to quantify the uncertainty associated with numerical inundation modelling and to properly propagate it onto the hazard results, to fully exploit the potential of site-specific hazard assessment based on massive simulations.

ABSTRACT Wu, E.C.; Chen, Y.L.; Wu, H.L.; Hu, K.C.; Hsiao, S.C., and Wu, Y.C., 2018. Incorporating Tidal Uncertainty into the Methodology of Probabilistic Tsunami Hazard Analysis. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 691–695. Coconut Creek (Florida), ISSN 0749-0208. The Circum-Pacific Belt has become active in recent years, and the earthquake in the border area of land and sea probably causes tsunami disaster. The hazard includes overflow flooded, building damage, casualties, and radiation crisis of nuclear power plant. To quantify the risk, probabilistic tsunami hazard analysis (PTHA) serves as a robust methodology. The uncertainty stemming from the deviation of modeling, named aleatory uncertainty, is considered with including the tidal effect on the tsunami. To deal with the aleatory uncertainty, we incorporate tidal uncertainty into PTHA. Different static tidal stages are set in Cornell Multi-grid Coupled Tsunami model (COMCOT) to evaluate tsunami hazards. Three kinds of method are presented. One could apply theoretical probability distribution to different maximum wave height by the Gaussian Method. On the other hand, the Δt method and the Pattern Method combine tsunami events with a typical year of tidal record. The difference between these methods are discussed, and the Pattern Method is regarded as the most rigorous way. Finally, the method of incorporating tidal uncertainty into PTHA has been established and been utilized to Maanshan nuclear power plant in Taiwan. [ABSTRACT FROM AUTHOR]

Wu, E.C.; Ma, W.H., Chen, Y.L.; Wu, H.L.; Hu, K.C.; Hsiao, S.C. and Wu, Y.C., 2016. Probabilistic Tsunami Hazard Analysis - Application to Maanshan Nuclear Power Plant in Taiwan. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1267 - 1271. Coconut Creek (Florida), ISSN 0749-0208. In the past twelve years, two earthquakes of magnitude 9.0 have occurred in the western Pacific. These earthquakes resulted in tsunamis, causing tremendous casualties, such as the nuclear disaster in Japan on March, 2011. Taiwan is an island located in the circum-Pacific belt, along which approximately 90% of the world's largest earthquakes take place. To prevent hazards, probabilistic tsunami hazard analysis (PTHA) is applied to nuclear power plants in the coastal regions of Taiwan. The approach developed here allows for the selection of reasonable tsunamis generated from distant earthquakes in the Manila Trench. Two types of uncertainty are considered: aleatory uncertainty and epistemic uncertainty. Concerning the aleatory uncertainty of modeling, a validation of prediction results is conducted against observed data. And a logic tree is introduced to help with epistemic uncertainty and set up different series of source parameters. In addition, a numerical model is used to simulate tsunami propagation and wave height. Under the assumptions of the logic tree and numerical modeling, the relationship between annual probability and maximum tsunami wave height can be obtained. Finally, tsunami hazard maps can be produced and the safety assessment of nuclear power plants can be carried out. The results provide useful information for engineering design and hazard prevention. [ABSTRACT FROM AUTHOR]

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

The study of tsunami hazards in Thailand has been an ongoing topic of research. However, the hazards from tsunami sources based on probabilistic study and population risk are still unclear. In this study, potential tsunami sources along rupture zones were selected. A series of far-field tsunami simulations were performed with scaled fault parameters based on fault lengths from 100-600 km. The results show that within a few centuries, the maximum tsunami height could be 2-5 m at the west coast and less than 2 m at the east coast. The potential tsunami exposure (PTE) of populations in an estimated inundation zone was calculated using global population data in relation to tsunami height. The results show that much attention should be paid to fault ruptures longer than 300 km (≈ 8.5 moment magnitude, Mw) that originate from 4°-6° N and 14°-17° N for the Sumatra subduction zone and the Manila trench, respectively. A quarter of a million people are at risk of exposure to a maximum 9 m tsunami height after 100 min of the arrival of the first wave at the Andaman coast. One million people near the Gulf of Thailand are at risk of a tsunami height less than 3 m after 9 hr. [ABSTRACT FROM AUTHOR]

This paper proposes a novel response surface-based method for probabilistic tsunami hazard assessment (PTHA). Although recent advancements in numerical simulation have enabled the accurate characterization of tsunami hazards, the high computational cost of numerical simulation often prohibits its broad application to probabilistic hazard analysis. The proposed method addresses this challenge by constructing the response surface (RS) of a target output using the results of high-fidelity tsunami simulations. The proposed method quantifies uncertainties in key simulation variables and propagates those uncertainties to the target output through the RS in a computationally efficient Monte Carlo simulation (MCS). We illustrate and validate the proposed method through a case study of the tsunami induced by the 2011 Great East Japan earthquake. The case study focuses on Sendai, Ishinomaki, and Kamaishi in Japan as the target locations. The proposed method estimates coastal tsunami heights while considering uncertainties in the fault slip and rake as well as the modeling error associated with the numerical simulation. The MCS allows us to estimate the probability density functions of the tsunami height at the target locations. The proposed method quantifies the contribution of each source of uncertainty to the overall uncertainty in the target output and thus facilitates engineering decision-making. • A novel method for probabilistic tsunami hazard assessment (PTHA) is proposed. • The method constructs a response surface using high-fidelity numerical simulations. • The method propagates uncertainties in key simulation variables to a target output. • The method enables a computationally efficient Monte Carlo simulation for PTHA. [ABSTRACT FROM AUTHOR]