Abstract
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.
Highlights
The standard way to estimate tsunami inundation maps is to apply numerical nonlinear shallow water (NLSW) models that include drying-wetting schemes (Titov and Gonzalez 1997; LeVeque and George 2008; Løvholt et al 2010; Dutykh et al 2011; de la Asuncion et al 2013; Wronna et al 2015; Macıas et al 2017)
The new version represents a major upgrade compared to previous amplification factor (AF) models, by taking into account the local bathymetry and the uncertainty introduced by using an approximated approach to the inundation process estimation through NLSW models
Because of the new AF capabilities, we can for the first time properly estimate the probability distribution of the maximum inundation height for probabilistic tsunami hazard analysis (PTHA)
Summary
(NLSW) models that include drying-wetting schemes (Titov and Gonzalez 1997; LeVeque and George 2008; Løvholt et al 2010; Dutykh et al 2011; de la Asuncion et al 2013; Wronna et al 2015; Macıas et al 2017). The AF method is designed to operate over large stretches of coastline, and the spatial resolution is much coarser than in numerical tsunami inundation models Local phenomena such as wave focusing and refraction usually give rise to significant local variability in the MIH that cannot be captured by the AF method, which assumes plane wave amplification. Davies et al (2018) estimated the AF uncertainty and bias by comparing offshore tsunami simulations combined with AF analysis against observed run-up for four tsunamigenic earthquakes (Chile, 1960; Alaska, 1964; Indian Ocean, 2004; Tohoku, 2011) using the previous AF version based on idealized and much simplified bathymetric transects. This paper is organized as follows: Section 2 describes the computation of the local amplification
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