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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. [ABSTRACT FROM AUTHOR]

The Mexican subduction zone is prone to large earthquakes that impact populated coastal and inland cities due to strong shaking and can generate potentially disastrous tsunamis. Even though the population and infrastructure on the Mexican Pacific coast may experience tsunamis, only sparse instrumentation and scarce tsunami observations exist for both, historical and instrumental, records. This study presents a probabilistic tsunami hazard analysis that can provide information for managing and assessing risks in the region. We use ensembles of numerical tsunami simulations to estimate the probability of exceedance of the maximum tsunami amplitudes, considering the contribution of near sources and slip heterogeneities, for return periods of 100, 500, and 1,000 years. According to 7,946 simulated scenarios, the amplitudes can reach up to 9.5 m along the shoreline. Moreover, tsunami hazard maps, curves, and disaggregation analyses reveal critical hazard points along the coasts of the states of Jalisco, Colima, Michoacán, Guerrero, and Oaxaca. Plain Language Summary: Tsunamigenic earthquakes are a critical problem in active subduction zones due to the potential of spreading damage in coastal cities, and given the necessity of know the possible effects, hazard assessments have an important role. In this study, we employed an ensemble of scenarios generated from available geophysical and topographic databases for the Mexican Subduction Zone, to estimate and analyze tsunami hazard with curves and maps, by using the tsunami amplitudes recorded from numerical simulations. Finally, we remark the necessity of a constant re‐evaluation of tsunami hazard, due to amplitude sensibility with the resolution of databases, especially in Oaxaca and Chiapas states, where the databases are coarser. Key Points: An ensemble of stochastic slip models is generated by gathering geophysical databases for the Mexican subduction zone and ran a series of tsunami numerical simulationsThe authors estimated tsunami hazard curves and maps in the Mexican Pacific coast using numerical simulations that employed kinematic seafloor deformation models [ABSTRACT FROM AUTHOR]

Central Chile is exposed to tsunami hazard, and large earthquakes and tsunamis have occurred over the last 500 years. Tsunami hazard analysis in Chile has been traditionally implemented by means of a deterministic approach, which is based on historical events and uniform slip distribution. The objective of the present study is to improve tsunami hazard analysis in central Chile (30°S to 38°S). To encompass the purpose, stochastic earthquake scenarios of magnitude M w 8.8 to 9.2 were generated. Two different sets of stochastic tsunami scenarios were selected by means of the Stochastic Reduced Order Model (SROM), which were applied to Quintero bay to perform a Probabilistic Tsunami Hazard Analysis (PTHA). The results showed that PTHA of Quintero bay from stochastic tsunami scenarios agrees with paleotsunami records in the bay, while a deterministic tsunami scenario underestimated the hazard. Two sets (50 and 100 scenarios, respectively) give similar results when smaller return periods are analyzed. However, for larger return periods ( > 2000 yr) the set of 100 scenarios show better results consistent with previous paleoseismological findings. The methodology implemented here can be replicated in other seismic regions in Chile as well as in other active subduction zones, thus, both near field and far field events can be analyzed. [ABSTRACT FROM AUTHOR]

Regional and global tsunami hazard analysis requires simplified and efficient methods for estimating the tsunami inundation height and its related uncertainty. One such approach is the amplification factor (AF) method. Amplification factors describe the relation between offshore wave height and the maximum inundation height, as predicted by linearized plane wave models employed for incident waves with different wave characteristics. In this study, a new amplification factor method is developed that takes into account the offshore bathymetry proximal to the coastal site. The present AFs cover the North-Eastern Atlantic and Mediterranean (NEAM) region. The model is the first general approximate model that quantifies inundation height uncertainty. Uncertainty quantification is carried out by analyzing the inundation height variability in more than 500 high-resolution inundation simulations at six different coastal sites. The inundation simulations are undertaken with different earthquake sources in order to produce different wave period and polarity. We show that the probability density of the maximum inundation height can be modeled with a log-normal distribution, whose median is quite well predicted by the AF. It is further demonstrated that the associated maximum inundation height uncertainties are significant and must be accounted for in tsunami hazard analysis. The application to the recently developed TSUMAPS-NEAM probabilistic tsunami hazard analysis (PTHA) is presented as a use case. [ABSTRACT FROM AUTHOR]

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]