The Making of the NEAM Tsunami Hazard Model 2018 (NEAMTHM18)
Authors: Basili Roberto , Brizuela Beatriz , Herrero André , Iqbal Sarfraz , Lorito Stefano , Maesano Francesco Emanuele , Murphy Shane , Perfetti Paolo , Romano Fabrizio , Scala Antonio , Selva Jacopo , Taroni Matteo , Tiberti Mara Monica , Thio Hong Kie , Tonini Roberto , Volpe Manuela , Glimsdal Sylfest , Harbitz Carl Bonnevie , Løvholt Finn , Baptista Maria Ana , Carrilho Fernando , Matias Luis Manuel , Omira Rachid , Babeyko Andrey , Hoechner Andreas , Gürbüz Mücahit , Pekcan Onur , Yalçıner Ahmet , Canals Miquel , Lastras Galderic , Agalos Apostolos , Papadopoulos Gerassimos , Triantafyllou Ioanna , Benchekroun Sabah , Agrebi Jaouadi Hedi , Ben Abdallah Samir , Bouallegue Atef , Hamdi Hassene , Oueslati Foued , Amato Alessandro , Armigliato Alberto , Behrens Jörn , Davies Gareth , Di Bucci Daniela , Dolce Mauro , Geist Eric , Gonzalez Vida Jose Manuel , González Mauricio , Macías Sánchez Jorge , Meletti Carlo , Ozer Sozdinler Ceren , Pagani Marco , Parsons Tom , Polet Jascha , Power William , Sørensen Mathilde , Zaytsev Andrey 
Published: March 2021

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 &gt;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 &gt;3 m are on the coasts of Mauritania and Gulf of Cadiz. Overall, 30% of the POIs have MIH &gt;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.