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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 ∼95100 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). [ABSTRACT FROM AUTHOR]

Earthquake hazard analyses rely on the availability of seismogenic source models. These are designed in different 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 formed the basis for 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. The compiled dataset covers an area from the Mid-Atlantic Ridge to the Caucasus and from northern Africa to Iceland. It includes 1,248 crustal faults spanning a total length of ~95,100 km and four subduction systems, namely the Gibraltar, Calabrian, Hellenic, and Cyprus Arcs. The model focuses on an area encompassing a buffer of 300 km around all European countries (except for Overseas Countries and Territories, OTCs) 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, is distributed as machine-readable files using open standards (Open Geospatial Consortium). [ABSTRACT FROM AUTHOR]

Historical earthquakes are of major importance in the analysis of seismic hazards, in particular for stable continental regions. In this article, we propose a methodology that uses seismic scenarios to provide constraints on the location of the seismic source of historical earthquakes. Our methodology involves generating seismic scenarios for the proposed seismic sources and comparing the results to the observed intensity field of the earthquake. To avoid the bias related to strongly heterogeneously distributed datasets, we focus on data points that are useful in discriminating between competing ruptures. These data are identified by the spatial patterns of residuals between seismic scenarios produced for each source. We apply this methodology to a test event--the 1999 Athens earthquake--for which both the magnitude and location are constrained by independent data, and to the 1909 Benavente earthquake, for which the magnitude is constrained by seismological studies, but the location is uncertain due to the very poor azimuthal coverage available. Within its application limits, the proposed methodology was capable of identifying the source of the Athens earthquake amongst different ruptures located few kilometers apart. The analysis performed for the 1909 Benavente earthquake suggests that the eastern strand of the lower Tagus Valley fault zone is the most likely seismic source for earthquake, amongst those proposed in the literature. [ABSTRACT FROM AUTHOR]

The El Salvador earthquake of 13 February 2001 (Mw 6.6) caused tectonic rupture on the El Salvador fault zone (ESFZ). Right-lateral strike-slip surface rupture of the east-west trending fault zone had a maximum surface displacement of 0.60 m. No vertical component was observed. The earthquake resulted in widespread landslides in the epicentral area, where bedrock is composed of volcanic sediments, tephra, and weak ignimbrites. In the aftermath of the earthquake, widespread damage to houses and roads and the hazards posed by landslides captured the attention of responding agencies and scientists, and the presence of surface-fault rupture was overlooked. Additionally, the tectonic context in which the earthquake took place had not been clear until mapping of the ESFZ was completed for the present study. We identified several fault segments, the distribution of surface ruptures, the aftershock pattern, and fault-rupture scaling considerations that indicate the 21-km-long San Vicente segment ruptured in the 2001 event. Static Coulomb stress transfer models for the San Vicente rupture are consistent with both aftershock activity of the 2001 sequence and ongoing background seismicity in the region. At Mw 6.6, the 2001 earthquake was of only moderate magnitude, yet there was significant damage to the country's infrastructure, including buildings and roads, and numerous deaths and injuries. Thus, earthquake hazard and risk in the vicinity of the ESFZ, which straddles the city of San Salvador with a population of > 2 million, is high because even moderate-magnitude events can result in major damage, deaths, and injuries in the region. [ABSTRACT FROM AUTHOR]

Most catastrophic earthquakes occur along fast-moving faults, although some of them are triggered by slow-moving ones. Long paleoseismic histories are infrequent in the latter faults. Here, an exceptionally long paleoseismic record (more than 300 k.y.) of a slow-moving structure is presented for the southern tip of the Alhama de Murcia fault (Eastern Betic shear zone), which is characterized by morphological expression of current tectonic activity and by a lack of historical seismicity. At its tip, the fault divides into a splay with two main faults bounding the Góñar fault system. At this area, the condensed sedimentation and the distribution of the deformation in several structures provided us with more opportunities to obtain a complete paleoseismic record than at other segments of the fault. The tectonic deformation of the system was studied by an integrated structural, geomorphological, and paleoseismological approach. Stratigraphic and tectonic features at six paleoseismic trenches indicate that old alluvial units have been repeatedly folded and thrusted over younger ones along the different traces of the structure. The correlation of the event timing inferred for each of these trenches and the application of an improved protocol for the infrared stimulated luminescence (IRSL) dating of K-feldspar allowed us to constrain a paleoseismic record as old as 325 ka. We identified a minimum of six possible paleo-earthquakes of Mw = 6-7 and a maximum mean recurrence interval of 29 k.y. This provides compelling evidence for the underestimation of the seismic hazard in the region. [ABSTRACT FROM AUTHOR]