GNGTS 2018 - 37° Convegno Nazionale

300 GNGTS 2018 S essione 2.1 TESTING EMPIRICAL INUNDATION IN THE DEFINITION OF INUNDATION ZONES FOR TSUNAMI EARLY WARNING R. Tonini 1 , P. Di Manna 2 , B. Brizuela 1 , S. Lorito 1 , F. Løvholt 4 , A. Garcia 3 , A. Piatanesi 1 , F. Romano 1 , J. Selva 3 , E. Vittori 2 , M. Volpe 1 1 Istituto Nazionale Di Geofisica e Vulcanologia, Sezione di Roma 1, Roma, Italy 2 Istituto Superiore per la Protezione e la Ricerca Ambientale, Roma, Italy 3 Istituto Nazionale Di Geofisica e Vulcanologia, Sezione di Bologna, Bologna, Italy 4 Norwegian Geotechnical Institute, Oslo, Norway Numerical modelling is by far the most accredited method to model tsunami propagation and inundation. However, a massive use of tsunami inundation simulations on high-resolution numerical grids of coastal areas still represents a challenge in some practical applications, due to the expensive computational cost and the limited availability of very detailed topo- bathymetric digital elevation models (DEMs). Probabilistic tsunami hazard analyses (PTHAs) and, consequently, all the PTHA-derived products, have to deal with these issues and can require alternative approaches to evaluate the tsunami inundation in a given target area. Evacuation maps, ideally, need to represent all possible areas subject to inundation from all potential tsunami sources contributing to PTHA, for a given fixed average return period, and taking into account the high degree of uncertainty in tsunami source and inundation models. Alternatively, empirical or analytical simplified methods based on amplification factors and/ or coastal dissipation models can provide rapid approximated estimates. A common practice consists in physically modelling the tsunami waves offshore up to water depths of 50-100 m and, then, extrapolating by such methods the maximum offshore wave heights to some inundation distance and/or topographic elevation on land. In Italy, tsunami evacuation maps are being developed in the frame of the Italian Tsunami Alert System (SiAM), constituted by the Italian Civil Protection Department (DPC), the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the Italian Institute for Environmental Protection and Research (ISPRA). These evacuation maps are associated to actions to be taken, corresponding to Advisory (orange) and Watch (red) alert levels issued by the INGV Centro Allerta Tsunami (CAT-INGV) and disseminated by DPC. Input for the evacuation maps is the regional Seismic ProbabilisticTsunami HazardAnalysis (S-PTHA) developed in theTSUMAPS- NEAM project ( http://www.tsumaps-neam.eu/) , which provides the 50 yr probability of exceedance for the mean value on a given stretch of coast of the maximum inundation height (MIH) along profiles perpendicular to the coast. In TSUMAPS-NEAM, the MIH is obtained Fig. 1 - Sketch of the empirical inundation method: R is the maximum estimated run-up value, D is the inundation distance, the dissipation factor is tgα=0.005. The light blue line and the dark blue line indicate respectively the Advisory and Watch alert zones.