Vanneste, Kris

Abstract. Earthquake hazard analyses rely on seismogenic source models. These are designed in various fashions, such as point sources or area sources, but the most effective is the three-dimensional representation of geological faults. We here refer to such models as fault sources. This study presents the European Fault-Source Model 2020 (EFSM20), which was one of the primary input datasets of the recently released European Seismic Hazard Model 2020. The EFSM20 compilation was entirely based on reusable data from existing active fault regional compilations that were first blended and harmonized and then augmented by a set of derived parameters. These additional parameters were devised to enable users to formulate earthquake rate forecasts based on a seismic-moment balancing approach. EFSM20 considers two main categories of seismogenic faults: crustal faults and subduction systems, which include the subduction interface and intraslab faults. The compiled dataset covers an area from the Mid-Atlantic Ridge to the Caucasus and from northern Africa to Iceland. It includes 1248 crustal faults spanning a total length of ∼95 100 km and four subduction systems, namely the Gibraltar, Calabrian, Hellenic, and Cyprus arcs, for a total length of ∼2120 km. The model focuses on an area encompassing a buffer of 300 km around all European countries (except for Overseas Countries and Territories) and a maximum of 300 km depth for the subducting slabs. All the parameters required to develop a seismic source model for earthquake hazard analysis were determined for crustal faults and subduction systems. A statistical distribution of relevant seismotectonic parameters, such as faulting mechanisms, slip rates, moment rates, and prospective maximum magnitudes, is presented and discussed to address unsettled points in view of future updates and improvements. The dataset, identified by the DOI https://doi.org/10.13127/efsm20 (Basili et al., 2022), is distributed as machine-readable files using open standards (Open Geospatial Consortium).

The H2020 Project SERA (WP25-JRA3; http://www.sera-eu.org) is committed to updating and extending the 2013 European Seismic Hazard Model (ESHM13; Woessner et al., 2015, Bull. Earthquake Eng.) to form the basis of the next revision of the European seismic design code (CEN-EC8). Following the probabilistic framework established for ESHM13, the 2020 update (ESHM20) requires a continent-wide seismogenic model based on input from earthquake catalogs, tectonic information, and active faulting. The development of the European Fault-Source Model (EFSM20) fulfills the requirements related to active faulting. EFSM20 has two main categories of seismogenic faults: crustal faults and subduction systems. Crustal faults are meant to provide the hazard model with seismicity rates in a variety of tectonic contexts, including onshore and offshore active plate margins and plate interiors. Subduction systems are meant to provide the hazard model with both slab interface and intraslab seismicity rates. The model covers an area that encompasses a buffer of 300 km around all target European countries (except for Overseas Countries and Territories, OTCs), and a maximum of 300 km depth for slabs. The compilation of EFSM20 relies heavily on publicly available datasets and voluntarily contributed datasets spanning large regions, as well as solicited local contributions in specific areas of interest. The current status of the EFSM20 compilation includes 1,256 records of crustal faults for a total length of ~92,906 km and four subduction systems, namely the Gibraltar Arc, Calabrian Arc, Hellenic Arc, and Cyprus Arc. In this contribution, we present the curation of the main datasets and their associated information, the criteria for the prioritization and harmonization across the region, and the main strategy for transferring the earthquake fault-source input to the hazard modelers. The final version of EFSM20 will be made available through standard web services published in the EFEHR (http://www.efehr.org) and EPOS (https://www.seismofaults.eu) platforms adopting FAIR data principles. The SERA project received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No.730900.

More than 25 years have passed since the definition of Active Tectonics as "tectonic movements that are expected to occur within a future time span of concern to society", formulated in a milestone book by the National Research Council on this topic (Studies in Geophysics, Active Tectonics, National Academy Press, Washington, D.C. 1986), and those words have still to be considered the most suitable and exhaustive way to explain this branch of the Earth Sciences. Indeed only bridging together basic studies ("tectonic movements"), rates of occurrence ("time span") and hazard assessment ("society") can we fully evaluate ongoing tectonic activity and its associated hazards. The broad Mediterranean Sea region is a paradigmatic area from this point of view, as on one hand this region displays in a relatively limited geographic extent a great variety of tectonic processes such as plate collision, subduction, volcanic activity, large-magnitude earthquakes, active folding and faulting, vertical uplift and/or subsidence. On the other hand, all the above mentioned tectonic processes can potentially affect a total population of about 450 million, mostly concentrated in fast-growing urban areas and/or close to industrial compounds and critical facilities often located nearby hazard sources.