The Alpine Pyrenean‐Cantabrian orogen developed along the plate boundary between Iberia and Europe, involving the inversion of Mesozoic hyperextended basins along the southern Biscay margin. Thus, this margin represents a natural laboratory to analyze the control of structural rift inheritance on the compressional reactivation of a continental margin. With the aim to identify former rift domains and investigate their role during the subsequent compression, we performed a structural analysis of the central and western North Iberian margin, based on the interpretation of seismic reflection profiles and local constraints from drill‐hole data. Seismic interpretations and published seismic velocity models enabled the development of crustal thickness maps that helped to constrain further the offshore and onshore segmentation. Based on all these constraints, we present a rift domain map across the central and western North Iberian margin, as far as the adjacent western Cantabrian Mountains. Furthermore, we provide a first‐order description of the margin segmentation resulting from its polyphase tectonic evolution. The most striking result is the presence of a hyperthinned domain (e.g., Asturian Basin) along the central continental platform that is bounded to the north by the Le Danois High, interpreted as a rift‐related continental block separating two distinctive hyperextended domains. From the analysis of the rift domain map and the distribution of reactivation structures, we conclude that the landward limit of the necking domain and the hyperextended domains, respectively, guide and localize the compressional overprint. The Le Danois block acted as a local buttress, conditioning the inversion of the Asturian Basin.
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Mapping and distribution with depth of alteration in rocks is critical in engineering planning because it has a fundamental impact on the geotechnical properties of the materials. Lateral heterogeneity on a weathered rock massif makes boreholes inadequate for its complete characterization. Geophysical methods increase spatial sampling along the study area and can be related to geotechnical parameters, so subsoil conditions can be better understood.In order to determine its geotechnical qualities and variability along two different profiles, we attempt to characterize a granite massif in north‐west Spain by the integration of results from seismic refraction, multichannel analysis of surface waves (MASW) and electrical resistivity tomography methods (ERT). The study area, the so‐called Carlés granite, shows all the weathering grades from sandy soil to fresh rock. A reference borehole where samples were taken and laboratory measurements were made, serves as a direct check for the results of one of the profiles, the other being interpreted without any direct information. This approach has permitted the evaluation of the advantages and limitations of each geophysical method and created an accurate geotechnical model of the massif, correlating physical and geotechnical parameters such as rock quality designation, weathering grade, or standard penetration test.The field seismic velocities have been compared with the ultrasonic measurements at the laboratory, permitting an evaluation of the field and laboratory elastic constants. The trend in the values of these parameters agrees with the field and laboratory test for the shallow parts of the massif. However, unrealistic elastic constants have been obtained for fresh rock based on the results of the field experiments. This is related to an apparent underestimation of the velocity of seismic S‐waves for the deepest layers. This fact suggests that the methodology followed throughout this work is able to provide a full geotechnical model of an altered rock massif for the first tens of metres, discriminating between different weathered levels. It is also useful and reliable when inferring elastic constants for depths of up to 20 m. However, its validity becomes doubtful with depth, so care must be taken when calculating elastic moduli and trying to extrapolate directly to a rock massif.
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