Insights into the lithospheric architecture of Iberia and Morocco from teleseismic body-wave attenuation

The long and often complicated tectonic history of continental lithosphere results in lateral strength heterogeneities which in turn affect the style and localization of deformation. In this study, we produce a model for the attenuation structure of Iberia and northern Morocco using a waveform-matching approach on P-wave data from teleseismic deep-focus earthquakes. We find that attenuation is correlated with zones of intraplate deformation and seismicity, but do not find a consistent relationship between attenuation and recent volcanism. The main features of our model are low to moderate Δt⁎ in the undeformed Tertiary basins of Spain and high Δt⁎ in areas deformed by the Alpine orogeny. Additionally, low Δt⁎ is found in areas where the Alboran slab is thought to be attached to the Iberian and African lithosphere, and high Δt⁎ where it has detached. These features are robust with respect to inversion parameters, and are consistent with independent data. Very mild backazimuthal dependence of the measurements and comparison with previous results suggest that the source of the attenuation is sub-crustal. In line with other recent studies, the range of Δt⁎ we observe is much larger than can be expected from lithospheric thickness or temperature variations.