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Perea, Héctor . et al.-- 11 pages, 8 figures, 2 tables, supplementary data https://doi.org/10.1016/j.margeo.2018.02.002 ; Complex multifault earthquake ruptures involving secondary faults emphasize the necessity to characterize their seismogenic potential better and study their relationship with major faults to improve the seismic hazard assessment of a region. High-resolution geophysical data were interpreted to make a detailed characterization of the Averroes Fault and the North Averroes Faults, which are poorly known secondary right-lateral strike-slip faults located in the central part of the Alboran Sea (western Mediterranean). These faults appear to have evolved since the Pliocene as part of a distributed dextral strike-slip shear zone in response to local strain engendered by the diverging movement of the Carboneras Fault to the north, and the Yusuf and Alboran Ridge faults to the south. In addition, the architecture of these faults suggests that the Averroes Fault may eventually link with the Yusuf fault, thus leading to a higher seismogenic potential. Therefore, these secondary faults represent a hitherto unrecognized seismogenic hazard since they could produce earthquakes up to moment magnitude (M) 7.6. Our results highlight the importance of the role played by secondary faults in a specific kinematic framework. Their reciprocal linkage and their mechanical relationship with the main faults could lead to future complex fault ruptures. This information could improve fault source and earthquake models used in seismic and tsunami hazard assessment in this and similar regions ; This research was supported by IMPULS (REN2003-05996MAR), EVENT (CGL2006-12861-C02-02), SHAKE (CGL2011-30005-C02-02), INSIGHT (CTM2015-70155-R) projects, the EU-COST Action FLOWS (ES 1301) and the European Union's Horizon 2020 research and innovation programme under grant agreement No H2020-MSCA-IF-2014 657769. Hector Perea was a fellow researcher under the "Juan de la Cierva" program (JCI-2010-07502) and under the Marie Sklodowska-Curie Actions (H2020-MSCA-IF-2014 657769) ; Peer Reviewed

19 pages, 8 figures, supporting information https://doi.org/10.1029/2020JB019854.-- Data Availability Statement. The WESTMED data are archived at PANGAEA repository (https://doi.pangaea.de/10.1594/PANGAEA.921252), GEBCO bathymetry grid (https://doi.org/10.5285/a29c5465‐b138‐234d‐e053‐6c86abc040b9), and SRTM bathymetry/topography grid (https://doi.org/10.5067/MEaSUREs/SRTM/SRTMGL1.003) ; In continental settings, seismic failure is generally restricted to crustal depth. Crustal structure is therefore an important proxy to evaluate seismic hazard of continental fault systems. Here we present a seismic velocity model across the Gibraltar Arc System, from the Eurasian Betics Range (South Iberian margin), across offshore East Alboran and Pytheas (African margin) basins, and ending onshore in North Morocco. Our results reveal the nature and configuration of the crust supporting the coexistence of three different crustal domains: the continental crust of the Betics, the continental crust of the Pytheas Basin (south Alboran Basin) and onshore Morocco, and a distinct domain formed of magmatic arc crust under the East Alboran Basin. The magmatic arc under the East Alboran Basin is characterized by a velocity structure containing a relatively high‐velocity lower crust (~7 km/s) bounded at the top and base by reflections. The lateral extension of this crust is mapped integrating a second perpendicular wide‐angle seismic profile along the Eastern Alboran basin, together with basement samples, multibeam bathymetry, and a grid of deep‐penetrating multichannel seismic profiles. The transition between crustal domains is currently unrelated to extensional and magmatic processes that formed the basin. The abrupt transition zones between the different crustal domains support that they are bounded by crustal‐scale active fault systems that reactivate inherited structures. Seismicity in the area is constrained to upper‐middle crust depths, and most earthquakes nucleate outside of the magmatic arc domain ; This work is supported by the Cluster of Excellence "The Future Ocean", within the framework of the Excellence Initiative by the Deutsche Forschungsgemeinschaft (DFG) on behalf of the German federal and state governments. Efforts benefitted from funding of the German Science Foundation (DFG Grants GR1964/12‐1, RA 925/2‐1+2‐2, and RE 873/17‐1). The TOPOMED cruise was part of the EUROMARGINS and TOPO‐EUROPE initiatives of the EUROCORES Programme of the European Science Foundation (ESF). This study benefitted from an EU Marie Skłodowska‐Curie Individual Fellowship to L. Gómez de la Peña (H2020‐MSCA‐IF‐2017 796013). The Spanish Science and Innovation Ministry funded C. R. Ranero through the project FRAME CTM2015‐71766‐R and G. Booth‐Rea through the project PID2019‐107138RB‐I00. This is a contribution of the Barcelona Center for Subsurface Imaging, Grup de Recerca 2017 SGR 1662, Generalitat de Catalunya ; Peer reviewed

15 pages, 10 figures, 3 tables, supplementary material https://doi.org/10.1016/j.margeo.2022.106749.-- Data availability: The data (3D complex mesh of the ARFS and rake values, and the resulting grid files of the tsunami simulations containing the maximum wave amplitude) are archived at PANGAEA repository (https://doi.pangaea.de/10.1594/PANGAEA.941092).-- The EMODnet bathymetry is available at https://www.emodnet-bathymetry.eu/. The stochastic slip distributions have been produced by the code ANTI-FASc (https://github.com/antonioscalaunina/ANTI-FASc) a platform partially based on the code k223d (Herrero and Murphy, 2018 available at https://github.com/s-murfy/k223d), in turn based on the slipk2 (available at https://github.com/andherit/slipk2) and the trilateration codes (available at https://github.com/andherit/trilateration) ; The westernmost Mediterranean hosts part of the plate boundary between the European and African tectonic plates. Based on the scattered instrumental seismicity, this boundary has been traditionally interpreted as a wide zone of diffuse deformation. However, recent seismic images and seafloor mapping studies support that most of the plate convergence may be accommodated in a few tectonic structures, rather than in a broad region. Historical earthquakes with magnitudes Mw > 6 and historical tsunamis support that the low-to-moderate instrumental seismicity might also have led to underestimation of the seismogenic and tsunamigenic potential of the area. We evaluate the largest active faults of the westernmost Mediterranean: the reverse Alboran Ridge, and the strike-slip Carboneras, Yusuf and Al-Idrissi fault systems. For the first time, we use a dense grid of modern seismic data to characterize the entire dimensions of the main fault systems, accurately describe the geometry of these structures and estimate their seismic source parameters. Tsunami scenarios have been tested based on 3D-surfaces and seismic source parameters, using both uniform and heterogeneous slip distributions. The comparison of our results with previous studies, based on limited information on the fault geometry and kinematics, indicates that accurate fault geometries and heterogeneous slip distributions are needed to properly assess the seismic and tsunamigenic potential in this area. Based on fault scaling relations, the four fault systems have a large seismogenic potential, being able to generate earthquakes with Mw > 7. The reverse Alboran Ridge Fault System has the largest tsunamigenic potential, being able to generate a tsunami wave amplitude greater than 3 m in front of the coasts of Southern Spain and Northern Africa ; This work is supported by the Cluster of Excellence "The Future Ocean", within the framework of the Excellence Initiative by the Deutsche Forschungsgemeinschaft (DFG) on behalf of the German federal and state governments. This study benefited from an EU Marie Skłodowska-Curie Individual Fellowship to LGP (H2020-MSCA-IF-2017 796013). LGP, CS, FM and RB acknowledge the resources made available by the SISMOLAB-3D at INGV. This work has been carried out in collaboration with the Grup de Recerca Consolidat de la Generalitat de Catalunya "Barcelona Center for Subsurface Imaging" (2017 SGR 1662), and acknowledges the ICM "Severo Ochoa Centre of Excellence" accreditation (CEX2019-000928-S) ; Peer reviewed

19 pages, 9 figures, 1 table, supporting information https://doi. org/10.1029/2021JB022127.-- Data Availability Statement: Fault meshes and Slip distributions are available at the figshare repository: https://figshare.com/s/02e19886d2ded8ec9145. MCS data is available at the following published articles: SWIM profiles: Bartolome et al., (2012); Martínez-Loriente (2013); Martínez-Loriente et al., (2013); Martínez-Loriente et al., (2018). VOLTAIRE profiles: Banda et al., (1995); Zitellini et al., (2001); Terrinha et al., (2009). BIGSETS profiles: Zitellini et al., (2001); Zitellini et al., (2004); Vizcaino (2009); Serra et al., (2020). IAM profiles: Sartori et al., (1994); Jiménez-Munt et al., (2010); Terrinha et al., (2009); Zitellini et al., (2009). ARRIFANO profiles: Sartori et al., (1994); Zitellini et al., (2004); Serra et al., (2020). Bathymetry used for the tsunami simulations (Figures 3-7) is available in the SRTM public repository: https://www2.jpl.nasa.gov/srtm/. Detailed bathymetry used to define the fault traces is published in Zitellini et al., 2009. Seismicity data used in Figure 1a is available at the IGN catalog website: https://www.ign.es/web/ign/portal/sis-catalogo-terremotos ; The SW Iberian margin is one of the most seismogenic and tsunamigenic areas in W-Europe, where large historical and instrumental destructive events occurred. To evaluate the sensitivity of the tsunami impact on the coast of SW Iberia and NW Morocco to the fault geometry and slip distribution for local earthquakes, we carried out a set of tsunami simulations considering some of the main known active crustal faults in the region: the Gorringe Bank (GBF), Marquês de Pombal (MPF), Horseshoe (HF), North Coral Patch (NCPF) and South Coral Patch (SCPF) thrust faults, and the Lineament South strike-slip fault. We started by considering for all of them relatively simple planar faults featuring with uniform slip distribution; we then used a more complex 3D fault geometry for the faults constrained with a large 2D multichannel seismic dataset (MPF, HF, NCPF, and SCPF); and finally, we used various heterogeneous slip distributions for the HF. Our results show that using more complex 3D fault geometries and slip distributions, the peak wave height at the coastline can double compared to simpler tsunami source scenarios from planar fault geometries. Existing tsunami hazard models in the region use homogeneous slip distributions on planar faults as initial conditions for tsunami simulations and therefore underestimate tsunami hazard. Complex 3D fault geometries and non-uniform slip distribution should be considered in future tsunami hazard updates. The tsunami simulations also support the finding that submarine canyons attenuate the wave height reaching the coastline, while submarine ridges and shallow shelves have the opposite effect ; The authors are grateful for funding from MINECO through the project INSIGHT (CTM2015-70155-R), the project STRENGTH (PID2019-104668RB-I00), a MINECO FPI-2016 grant (BES-2016-078877) to Cristina S. Serra (ICM-CSIC), a MICINN "Juan de la Cierva-2017" grant (IJCI-2017-33838) to Sara Martinez-Loriente (ICM-CSIC), and from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2019-000928-S). We acknowledge the resources made available by the SISMOLAB-3D at INGV for the 3D fault modeling ; Peer reviewed