Moment tensor inversion for Iberia–Maghreb earthquakes 2005–2008

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]