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We present the first rupture models of the two mainshocks of the 2012 northern Italy sequence, determined by jointly inverting seismic and geodetic data. We aim at providing new insights into the mainshocks for which contrasting seismotectonic interpretations are proposed in literature. Sources' geometric parameters were constrained by seismic reflection profiles, 3‐D relocations and focal mechanisms of mainshocks/aftershocks. Site‐specific velocity profiles were used to model accelerograms affected by strong propagation effects related to the Po basin. Our source models differ significantly from previous ones relying on either seismic or geodetic data. Their comparison against geological sections and aftershock distribution provides new insights about the ruptured thrust faults. The May 20th Mw6.1 mainshock activated the Middle Ferrara thrust‐ramp dipping ∼45° SSW‐wards, breaking a main eastern slip patch 4–15 km deep in Mesozoic carbonates (maximum slip 0.7–0.8 m) and Paleozoic‐Triassic basement rocks, and a small western patch in the basement. The May 29th Mw6.0 mainshock featured two separated asperities along the Mirandola thrust‐ramp dipping ∼42° S‐wards: an eastern asperity 4–15 km deep in Mesozoic carbonates and basement rocks (maximum slip 0.7 m) and a deeper western one (7–16 km depth) mainly in the basement (slip peak 0.8 m). On‐fault aftershocks were concentrated within the basement and Mesozoic carbonates, devoiding high‐slip zones. Slip and aftershock distribution was controlled by the rheological transition between Mesozoic carbonates and Cenozoic sediments. Unlike previous thin‐skinned tectonic interpretations, our results point to a complex rupture process along moderately dipping (40°–45°) thrust‐ramps deeply rooted into the Paleozoic crystalline basement. Plain Language Summary: The two M6 mainshocks of the 2012 Italy sequence are the strongest earthquakes ever observed in the Po Plain, a strategic region for the Italian economy. The mainshocks ruptured blind thrust‐faults, however their source models and seismotectonic interpretation are still debated because the thrust‐system architecture is controversial. Contrasting thick‐skinned and thin‐skinned tectonic models are proposed. In thick‐skinned interpretations, shortening is accommodated by thrust‐ramps rooted into the crystalline basement that represent main seismogenic structures, whereas in thin‐skinned interpretations, shortening and seismicity are controlled by listric faults splaying out from dècollement levels in the sedimentary crust. A comprehensive analysis of the mainshocks' source represents an opportunity to provide new insights into the seismogenesis in northern Italy and on a broader scale into seismotectonics of thrust‐and‐fold belts. We get a complete picture of the mainshocks kinematics by jointly inverting, for the first time, seismic and geodetic data, and unravel rupture heterogeneities not resolved by previous studies. By integrating source models with aftershock locations and geological models, we propose a comprehensive seismotectonic interpretation of the sequence. We conclusively identify the ruptured faults that correspond to thrust‐ramps rooted into the crystalline basement and evidence the key role played by lithological changes in the rupture process. Key Points: Rupture models of the 2012 northern Italy mainshocks obtained by inverting the most comprehensive geodetic and strong motion data set to dateBoth mainshocks ruptured two asperities along moderately dipping thrusts rooted into the Paleozoic crystalline basement down to ∼15 km depthAsperities located in Mesozoic carbonates and Paleozoic basement and slip distribution controlled by lithological and structural barriers [ABSTRACT FROM AUTHOR]

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. Plain Language Summary: Deformation along the present‐day plate boundary between Africa and Eurasia off SW Iberia is distributed over a 200‐km‐wide and 600‐km‐long area, and is mainly accommodated by thrusts and strike‐slip faults. The region hosts frequent seismic activity of moderate magnitude punctuated by higher magnitude events, which have also originated major historical and pre‐historical tsunamis. The run‐up and coastal area affected by these tsunamis depend on the characteristics and location of the seismic source, bathymetry, and morphology of the coasts. Previous tsunami hazard assessments in the region used simplified fault models for tsunami simulations, ignoring the detailed 3D fault geometry and slip distribution. To investigate the sensitivity of the tsunami impact and eventually of the hazard to these complexities, we have carried out a series of tsunami simulations using planar and 3D fault surfaces, as well as homogeneous and heterogeneous slips. To build the fault surfaces, we used a large dataset of 2D multichannel seismic profiles that images the active faults in the region. Our study indicates that using the more complex fault models produce significantly larger tsunamis with the modeled wave heights at the coastline that can be several times bigger than those generated using planar fault sources. Key Points: The tsunami is sensitive to both the fault geometry and the slip distributionIntroducing complexity into the fault geometry and slip distribution can strongly enhance the simulated wave height at the coastOversimplified source models may hinder the prediction of the tsunami intensity, hence the tsunami hazard analysis [ABSTRACT FROM AUTHOR]