Seismic Constraints on the Western Mediterranean Geodynamics.

Speaker: Ramon Carbonell
“A large scale research initiative has been develloped within the Iberia Peninsula, Topo-Iberia. This aims to unravel the complex structure and mantle processes in the area of interaction between the African and European continental plates in the western Mediterranean. The project, funded by the Spanish Ministry of Science and Education, started in 2007 and will be active till Fall 2013. Topo-Iberia has gathered expertise of different fields of the Earth Sciences. One of the key assets of the project involves the deploying of a technological observatory platform, IberArray, with unprecedented resolution and coverage. This platform is currently building up a comprehensive, multidisciplinary data set, stored by the SIGEOF database, which includes seismological, GPS and magnetotelluric data. Using also other analytical methodologies included in the Topo-Iberia program (potential fields, quantitative analysis of the topography, dating methods) the final scope of the project is to study the relationship between superficial and deep-rooted processes. Topo-Iberia has also benefited from the interaction with other projects investigating the same area, as the American program PICASSO, the French Pyrope or the Portuguese WILAS. This interaction includes sharing the available data to better assess the key geological questions. The current state of the most significant scientific results which are arising from the data acquired using the Iberarray platform include:
-. SKS splitting analysis has provided a spectacular image of the anisotropic pattern over the area, including a clear rotation of the fast velocity direction along the Gibraltar Arc.
-. Receiver functions have revealed the crustal thickness variations beneath the Rif and southern Iberia, including a crustal root beneath the Rif not clearly documented previously. The 410-km and 660-km upper mantle discontinuities have been investigated using novel cross-correlation/stacking techniques.
-. Surface wave tomography using both earthquakes and ambient noise allows describing the main characteristics of crustal structure. Local body-wave tomography, currently focused on Northern Morocco, has improved the location of the small magnitude events affecting the area and the details of the crustal structure. Teleseismic tomography has confirmed, using an independent data set, the presence of a high-velocity slab beneath the Gibraltar Arc.
-. A number of 2-D Magnetotelluric (MT) profiles have been acquired in Iberia and Morocco. These MT profiles provide a 1500 km long N-S lithospheric transect extending from the Cantabrian Mountains to the Atlas.
-. The Topoiberia GPS deployments acquired long-term time series of data allowing well resolved determinations of the relatively small velocity displacements affecting the region.
-.Additional high-resolution active-source seismic experiments recently carried out in the Atlas, the Rif and the Central and Iberian Massifs piggy back with this large scale project are complementing this multidisciplinary data base.”