Abruzzi region (central Italy) producing vast damage in the L'Aquila town and surroundings. In this paper we present the location and geometry of the fault system as obtained by the analysis of main shock and aftershocks recorded by permanent and temporary networks. The distribution of aftershocks, 712 selected events with M L ! 2.3 and 20 with M L ! 4.0, defines a complex, 40 km long, NW trending extensional structure. The main shock fault segment extends for 15-18 km and dips at 45°to the SW, between 10 and 2 km depth. The extent of aftershocks coincides with the surface trace of the Paganica fault, a poorly known normal fault that, after the event, has been quoted to accommodate the extension of the area. We observe a migration of seismicity to the north on an echelon fault that can rupture in future large earthquakes.
Combining tectonics, with seismological and geochemical data, we reconstruct the deformation history of the presently narrow Calabrian slab and the path of mantle circulation during the last 10 Ma. We show that during the slab deformation the mantle laterally flowed inside the back arc region permitting its retrograde motion and giving a seismological and volcanological record after 1–2 myr
SKS‐wave birefringence is likely caused by ongoing and/or fossil mantle flow. Splitting parameters in the southern Tyrrhenian subduction zone define a quite complex pattern of fast directions with large delay times up to 2.7 s. Fast directions are prevalently trench parallel below the slab and rotate to trench normal at the western edge of the slab depicting a ring around it. We interpret these anisotropic patterns, also observed in laboratory experiment, as toroidal mantle flow induced by rollback subduction.
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