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The NEAM Tsunami Hazard Model 2018 (NEAMTHM18) is a probabilistic hazard model for tsunamis generated by earthquakes. It covers the coastlines of the North-eastern Atlantic, the Mediterranean, and connected seas (NEAM). NEAMTHM18 was designed as a three-phase project. The first two phases were dedicated to the model development and hazard calculations, following a formalized decision-making process based on a multiple-expert protocol. The third phase was dedicated to documentation and dissemination. The hazard assessment workflow was structured in Steps and Levels. There are four Steps: Step-1) probabilistic earthquake model; Step-2) tsunami generation and modeling in deep water; Step-3) shoaling and inundation; Step-4) hazard aggregation and uncertainty quantification. Each Step includes a different number of Levels. Level-0 always describes the input data; the other Levels describe the intermediate results needed to proceed from one Step to another. Alternative datasets and models were considered in the implementation. The epistemic hazard uncertainty was quantified through an ensemble modeling technique accounting for alternative models’ weights and yielding a distribution of hazard curves represented by the mean and various percentiles. Hazard curves were calculated at 2,343 Points of Interest (POI) distributed at an average spacing of ∼20 km. Precalculated probability maps for five maximum inundation heights (MIH) and hazard intensity maps for five average return periods (ARP) were produced from hazard curves. In the entire NEAM Region, MIHs of several meters are rare but not impossible. Considering a 2% probability of exceedance in 50 years (ARP≈2,475 years), the POIs with MIH >5 m are fewer than 1% and are all in the Mediterranean on Libya, Egypt, Cyprus, and Greece coasts. In the North-East Atlantic, POIs with MIH >3 m are on the coasts of Mauritania and Gulf of Cadiz. Overall, 30% of the POIs have MIH >1 m. NEAMTHM18 results and documentation are available through the TSUMAPS-NEAM project website (http://www.tsumaps-neam.eu/), featuring an interactive web mapper. Although the NEAMTHM18 cannot substitute in-depth analyses at local scales, it represents the first action to start local and more detailed hazard and risk assessments and contributes to designing evacuation maps for tsunami early warning. © Copyright © 2021 Basili, Brizuela, Herrero, Iqbal, Lorito, Maesano, Murphy, Perfetti, Romano, Scala, Selva, Taroni, Tiberti, Thio, Tonini, Volpe, Glimsdal, Harbitz, Løvholt, Baptista, Carrilho, Matias, Omira, Babeyko, Hoechner, Gürbüz, Pekcan, Yalçıner, Canals, Lastras, Agalos, Papadopoulos, Triantafyllou, Benchekroun, Agrebi Jaouadi, Ben Abdallah, Bouallegue, Hamdi, Oueslati, Amato, Armigliato, Behrens, Davies, Di Bucci, Dolce, Geist, Gonzalez Vida, González, Macías Sánchez, Meletti, Ozer Sozdinler, Pagani, Parsons, Polet, Power, Sørensen and Zaytsev.

The NEAM Tsunami Hazard Model 2018 (NEAMTHM18) is a probabilistic hazard model for tsunamis generated by earthquakes. It covers the coastlines of the North-eastern Atlantic, the Mediterranean, and connected seas (NEAM). NEAMTHM18 was designed as a three-phase project. The first two phases were dedicated to the model development and hazard calculations, following a formalized decision-making process based on a multiple-expert protocol. The third phase was dedicated to documentation and dissemination. The hazard assessment workflow was structured in Steps and Levels. There are four Steps: Step-1) probabilistic earthquake model; Step-2) tsunami generation and modeling in deep water; Step-3) shoaling and inundation; Step-4) hazard aggregation and uncertainty quantification. Each Step includes a different number of Levels. Level-0 always describes the input data; the other Levels describe the intermediate results needed to proceed from one Step to another. Alternative datasets and models were considered in the implementation. The epistemic hazard uncertainty was quantified through an ensemble modeling technique accounting for alternative models’ weights and yielding a distribution of hazard curves represented by the mean and various percentiles. Hazard curves were calculated at 2,343 Points of Interest (POI) distributed at an average spacing of ∼20 km. Precalculated probability maps for five maximum inundation heights (MIH) and hazard intensity maps for five average return periods (ARP) were produced from hazard curves. In the entire NEAM Region, MIHs of several meters are rare but not impossible. Considering a 2% probability of exceedance in 50 years (ARP≈2,475 years), the POIs with MIH >5 m are fewer than 1% and are all in the Mediterranean on Libya, Egypt, Cyprus, and Greece coasts. In the North-East Atlantic, POIs with MIH >3 m are on the coasts of Mauritania and Gulf of Cadiz. Overall, 30% of the POIs have MIH >1 m. NEAMTHM18 results and documentation are available through the TSUMAPS-NEAM project website (http://www.tsumaps-neam.eu/), featuring an interactive web mapper. Although the NEAMTHM18 cannot substitute in-depth analyses at local scales, it represents the first action to start local and more detailed hazard and risk assessments and contributes to designing evacuation maps for tsunami early warning.

International audience; Applying probabilistic methods to infrequent but devastating natural events is intrinsicallychallenging. For tsunami analyses, a suite of geophysical assessments should be in principle evaluatedbecause of the different causes generating tsunamis (earthquakes, landslides, volcanic activity,meteorological events, and asteroid impacts) with varying mean recurrence rates. Probabilistic TsunamiHazard Analyses (PTHAs) are conducted in different areas of the world at global, regional, and local scaleswith the aim of understanding tsunami hazard to inform tsunami risk reduction activities. PTHAs enhanceknowledge of the potential tsunamigenic threat by estimating the probability of exceeding specificlevels of tsunami intensity metrics (e.g., run-up or maximum inundation heights) within a certain period oftime (exposure time) at given locations (target sites); these estimates can be summarized in hazard mapsor hazard curves. This discussion presents a broad overview of PTHA, including (i) sources and mechanismsof tsunami generation, emphasizing the variety and complexity of the tsunami sources and their generationmechanisms, (ii) developments in modeling the propagation and impact of tsunami waves, and (iii)statistical procedures for tsunami hazard estimates that include the associated epistemic and aleatoricuncertainties. Key elements in understanding the potential tsunami hazard are discussed, in light of therapid development of PTHA methods during the last decade and the globally distributed applications,including the importance of considering multiple sources, their relative intensities, probabilities ofoccurrence, and uncertainties in an integrated and consistent probabilistic framework.