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.

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The Calabrian Arc is a one-of-a-kind subduction zone, featuring one of the shortest slab segments (<150 km), one of the thickest accretionary wedges, and one of the oldest oceanic crust in the world. Despite a convergence rate of up to 5 mm/y and well-known intraslab seismicity below 40 km, its shallow interface shows little signs of seismic activity. Nonetheless, it has been attributed as generating historical large earthquakes and tsunamis. To gain insights into this subduction zone, we first made a geological reconstruction of the shallower slab interface (<20 km) and its overlying accretionary wedge by interpreting a grid of 54 seismic reflection lines (8,658 km) with 438 intersections within an area of 105 km2. Then, we constrained a deeper portion of the slab surface (40–350 km) using the seismicity distribution. Finally, we interpolated the two parts to obtain a seamless 3D surface highlighting geometric details of the subduction interface, its lateral terminations and down-dip curvature, and a slab tear at 70–100 km depth. Our 3D slab model of the Calabrian Arc will contribute to understanding of the geodynamics of a cornerstone in the Mediterranean tectonic puzzle and estimates of seismic and tsunami hazards in the region.

Tsunami warning centres face the challenging task of rapidly forecasting tsunami threat immediately after an earthquake, when there is high uncertainty due to data deficiency. Here we introduce Probabilistic Tsunami Forecasting (PTF) for tsunami early warning. PTF explicitly treats data- and forecast-uncertainties, enabling alert level definitions according to any predefined level of conservatism, which is connected to the average balance of missed-vs-false-alarms. Impact forecasts and resulting recommendations become progressively less uncertain as new data become available. Here we report an implementation for near-source early warning and test it systematically by hindcasting the great 2010 M8.8 Maule (Chile) and the well-studied 2003 M6.8 Zemmouri-Boumerdes (Algeria) tsunamis, as well as all the Mediterranean earthquakes that triggered alert messages at the Italian Tsunami Warning Centre since its inception in 2015, demonstrating forecasting accuracy over a wide range of magnitudes and earthquake types.

The architecture of foreland basins and the resulting distribution of clastic sediments are related to the constant interplay between tectonics and sedimentation. Specifically, basin floor modifications strongly influence dimensions, continuity and connections of sand‐size and fine‐grained deposits. Given the increasing need to identify deep potential reservoir deposits, the large‐scale definition of clastic porous targets and their seals is a matter of interest for oil and gas industry. Here, we present the reconstruction of the Po Plain and Northern Adriatic Foreland Basin (with an extent of ca. 40,000 km2) and its Pliocene–Pleistocene evolution, as an example of a sedimentary clastic system controlled by strongly non‐cylindrical foreland geometry. The study is based on the basin‐scale mapping of six unconformity‐bounded sequences, performed by interpreting a dense network of seismic lines and correlating well‐log data. This provides a three‐dimensional model of the step‐by‐step evolution of the basin and a description of the sediment dispersal pattern. We found that the basin records the change from a continuous (cylindrical) to highly fragmented (non‐cylindrical) foredeep geometry during Late Pliocene. In the Northern Apennines case, the main factors driving the development of a non‐cylindrical geometry are mainly related to inherited inhomogeneity in the downgoing block linked to its Mesozoic extensional faulting, and the relative orientation of these lineaments with respect to the direction of orogen migration. During the late Pliocene–Pleistocene the two directions progressively became close to parallel, and the Northern Apennines system reacted changing from a cylindrical to a non‐cylindrical state.

The complexity of coseismic slip distributions influences the tsunami hazard posed by local and, to a certain extent, distant tsunami sources. Large slip concentrated in shallow patches was observed in recent tsunamigenic earthquakes, possibly due to dynamic amplification near the free surface, variable frictional conditions or other factors. We propose a method for incorporating enhanced shallow slip for subduction earthquakes while preventing systematic slip excess at shallow depths over one or more seismic cycles. The method uses the classic k-2 stochastic slip distributions, augmented by shallow slip amplification. It is necessary for deep events with lower slip to occur more often than shallow ones with amplified slip to balance the long-term cumulative slip. We evaluate the impact of this approach on tsunami hazard in the central and eastern Mediterranean Sea adopting a realistic 3D geometry for three subduction zones, by using it to model * 150,000 earthquakes with M w from 6.0 to 9.0. We combine earthquake rates, depth-dependent slip distributions, tsunami modeling, and epistemic uncertainty through an ensemble modeling technique. We found that the mean hazard curves obtained with our method show enhanced probabilities for larger inundation heights as compared to the curves derived from depthindependent slip distributions. Our approach is completely general and can be applied to any subduction zone in the world.

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We adopted a multidisciplinary approach to investigate the seismotectonic scenario of the 30 October 2016, Mw 6.5, Norcia earthquake, the largest shock of the 2016–2017 central Italy earthquake sequence. First, we used seismological and geodetic data to infer the dip of the main slip patch of the seismogenic fault that turned out to be rather low‐angle (~37°). To evaluate whether this is an acceptable dip for the main seismogenic source, we modeled earthquake deformation using single‐ and multiple‐fault models deduced from aftershock pattern analyses. These models show that the coseismic deformation generated by the Norcia earthquake is coherent with slip along a rather shallow‐dipping plane. To understand the geological significance of this solution, we reconstructed the subsurface architecture of the epicentral area. As the available data are not robust enough to converge on a single fault model, we built three different models encompassing all major geological evidence and the associated uncertainties, including the tectonic style and the location of major décollement levels. In all models the structures derived from the contractional phase play a significant role: from controlling segmentation to partially reusing inherited faults, to fully reactivating in extension a regional thrust, geometrically compatible with the source of the Norcia earthquake. Based on our conclusions, some additional seismogenic sources falling in the eastern, external portions of the Apennines may coincide with inherited structures. This may be a common occurrence in this region of the chain, where the inception of extension is as recent as Middle‐Upper Pleistocene.