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Abstract: We present and discuss a set of 77 moment tensor solutions for earthquakes in the Iberia–Maghreb region from mid 2005 to the end of 2008, with moment magnitudes ranging from 3.2 to 6.0. Inversion is based upon full, three-component, intermediate period waveforms recorded at regional seismic broadband stations. Following the recent densification of permanent broadband networks and large scale temporary deployments, at present more than 150 stations are recording in Spain, Portugal and Morocco. This unprecedented station density allows analysis of small events from available short-distance recordings, and in general leads to more reliable source estimates due to data redundancies that permit elimination of waveforms affected by noise or complicated propagation effects. The solutions for 2005–2008 constitute an important upgrade of the Iberia–Maghreb moment tensor inventory to 225 solutions to date, enhancing the image of seismotectonics at the compressive N-Algerian margin, in the Betic–Alboran shear zone and at the transpressive SW-Iberian margin, as well as providing valuable constraints on seismic deformation in the western Betics and the Iberian foreland where little information has been previously available. New solutions for the foreland and three recent seismic series in the western Betics show strike-slip and reverse faulting style, contrasting with the dominance of normal faulting in the adjacent areas towards east. In these areas, as well as at the SW-Iberian margin, faulting orientations are heterogeneous, including solutions with opposite kinematics. This indicates control by local stress conditions, and points to fault interaction. Along the N-Algerian margin, a counterclockwise rotation of slip vectors of thrust events from east to west becomes apparent. Several solutions for the area offshore Cape St. Vincent are located at sub-Moho depths between 40 and 60km, supporting a large brittle layer thickness in the oceanic lithosphere. [Copyright &y& Elsevier]

Examines the relative locations of multiplets in the vicinity of the Western Almerí earthquake series of 1993-1994 in Spain. Comparison of relative arrival times with possible selection of master event; Determination of relative epicenters; Indication of repeated slip on the same fault segment.

New seismic imaging and seismotectonic data from the southwest Iberian margin, the site of the present-day boundary between the European and African plates, reveal that active strike slip is occurring along two prominent lineaments that have recently been mapped using multibeam bathymetry. Multichannel seismic and subbottom profiler images acquired across the lineaments show seafloor displacements and active faulting to depths of at least 10 km and of a minimum length of 150 km. Seismic moment tensors show predominantly WNW--ESE rightlateral strike-slip motion, i.e., oblique to the direction of plate convergence. Estimates of earthquake source depths close to the fault planes indicate upper mantle (i.e., depths of 40--60 km) seismogenesis, implying the presence of old, thick, and brittle lithosphere. The estimated fault seismic parameters indicate that the faults are capable of generating great magnitude (Mw ≥ 8.0) earthquakes. Such large events raise the concomitant possibility of slope failures that have the potential to trigger tsunamis. Consequently, our findings identify an unreported earthquake and tsunami hazard for the Iberian and north African coastal areas. [ABSTRACT FROM AUTHOR]

Abstract: Active faults from the Campo de Dalías (SE Betic Cordillera) allow us to constrain the deformation styles involved in the development of segmented oblique-slip faults. This sector constitutes the widest outcrop of Plio-Quaternary sediments in the northern boundary of the Alboran Sea. It has emerged since the Late Pliocene, and therefore provides recent deformation markers that are not disturbed by erosive processes. The faults started to grow during the Pleistocene, reactivating previous hybrid joints, with a normal-dextral slip. We present a detailed map of the largest fault in the area, the Loma del Viento fault, comprising six onshore segments. Based on field work and aerial photography, the distributions of the contiguous joints have been mapped, and the joints reactivated as faults are identified. Some of these fault segments are hard-linked, and fault slip enhances toward the linkage sectors between them with associated sedimentary depocenters. An electrical tomography profile reveals the wedge geometry of a unit of Pleistocene conglomerates and red silts that were coevally deposited during the fault movement. Long-term slip rate in the central part of the fault is estimated at 0.07±0.03mm/y. In addition, a seismic crisis nucleated close to the Loma del Viento fault during November 2010 was recorded. Moment tensor analysis of the two mainshocks (Mw 3.5 and 4.2) provides a focal solution indicating a N120°E striking right-lateral strike-slip fault. The corrugated morphology of the Loma del Viento fault may have influenced its seismic behavior. Some of the fault segments are oblique to the general motion of the fault. These oblique segments would provide higher resistance against the general fault motion and could lock the fault, leading to accumulate elastic energy. [Copyright &y& Elsevier]

We study the crustal and lithospheric mantle structure under central Betics in the westernmost Mediterranean region by migrating P-receiver functions along a dense seismic profile (∼2 km interstation distance). The profile, North–South oriented, probes the crustal structure of different geological units, from the Alboran domain in the south with metamorphic rocks, through the External Zones with sedimentary rocks to the Variscan terrains of the Iberian Massif in the north. From north to south, the Moho depth increases from ∼30 km to ∼46 km underneath the Guadix basin, due to the underthrusting of the Iberian crust below the Alboran crust, and suddenly shallows to ∼30 km underneath the Internal Zones with a step of 17 km. This sharp Moho step correlates well with a lithospheric step of ∼40 km, where the thickness of the lithosphere changes abruptly from ∼100 km in the north to ∼50 km in the south. We interpret this sharp and prominent lithospheric step as the termination of the Iberian lithosphere caused by a near-vertical STEP (Subduction-Transform-Edge-Propagator) fault that continues towards the surface as a positive flower tectonic structure of crustal scale. This STEP fault is located at the northern edge of the narrow Westernmost Mediterranean subduction system facilitating the slab rollback motion towards the west. The sharp termination of the Iberian lithosphere occurs under the contact between the Alpujarride and the Nevado-Filabride complexes of the Alboran domain in an ENE-WSW right-lateral transpressive shear zone. The thickest crust and lithosphere do not correlate with the highest topography along the profile suggesting that this high topography is a combined effect of the positive flower structure, and the push up of the asthenosphere produced by the removal of the Iberian lithosphere. [ABSTRACT FROM AUTHOR]