The Calabrian Arc subduction complex in the Ionian Sea: Regional architecture, active deformation, and seismic hazard

We analyzed the structure and evolution of the external Calabrian Arc (CA) subduction complex through an integrated geophysical approach involving multichannel and single‐channel seismic data at different scales. Pre‐stack depth migrated crustal‐scale seismic profiles have been used to reconstruct the overall geometry of the subduction complex, i.e., depth of the basal detachment, geometry and structural style of different tectonic domains, and location and geometry of major faults. High‐resolution multichannel seismic (MCS) and sub‐bottom CHIRP profiles acquired in key areas during a recent cruise, as well as multibeam data, integrate deep data and constrain the fine structure of the accretionary wedge as well as the activity of individual fault strands. We identified four main morpho‐structural domains in the subduction complex: 1) the post‐Messinian accretionary wedge; 2) a slope terrace; 3) the pre‐Messinian accretionary wedge and 4) the inner plateau. Variation of structural style and seafloor morphology in these domains are related to different tectonic processes, such as frontal accretion, out‐of-sequence thrusting, underplating and complex faulting. The CA subduction complex is segmented longitudinally into two different lobes characterized by different structural style, deformation rates and basal detachment depths. They are delimited by a NW/SE deformation zone that accommodates differential movements of the Calabrian and the Peloritan portions of CA and represent a recent phase of plate re‐organization in the central Mediterranean. Although shallow thrust‐type seismicity along the CA is lacking, we identified active deformation of the shallowest sedimentary units at the wedge front and in the inner portions of the subduction complex. This implies that subduction could be active but aseismic or with a locked fault plane. On the other hand, if underthrusting of the African plate has stopped recently, active shortening may be accommodated through more distributed deformation. Our findings have consequences on seismic hazard, since we identified tectonic structures likely to have caused large earthquakes in the past and to be the source regions for future events

Appraisal of a new low frequency seismic pulse generating method on a deep seismic profile in the Mediterranean Sea

FIRST BREA

The CROP3 traverse: insights on post-collisional evolution of Northern Apennines.

MEM. SOC. GEOLOG. IT

Crustal structure of the ionian margin of Sicily: Etna volcano in the frame of regional evolution

Crustal imaging could be achieved on normal-incidence reflection profiles offshore eastern Sicily by using industrial-grade reflection seismic with improved marine sources. Thick recent sediments, a reflective pile including the Mesozoic deposits, a transparent upper crust, and a band of low frequency reflections attributed to the lower crust, are imaged in the seismic sections. The structure of the crust and its thickness show features inherited from the Mesozoic evolution as a passive margin, by which Ionian basin crust was formed around the Hyblean continental promontory of Africa to constitute the southern plate in the later convergence with Europe. The seismic images are also marked by the lithospheric deformation due to the Neogene overriding of the northern part of this paleomargin by the Calabro-Peloritan block of European continental crust. This transpressive motion may have been guided along the northern part of this paleomargin where the seismic profiles evidence a hinge line between the northward upslope of the Moho of that old passive margin and its downslope to the present slab under the Tyrrhenian Sea. Etna volcano is located at the intersection of this mantle upwarp by a zone of active sea-bottom normal-faults, which cut across the formerly constructed compressional belt. The onset of its volcanic activity is roughly coeval with that of the cessation of interplate thrusting and could hence be related to a change of the coupling of the Ionian slab. This slab is now probably disconnected from the overriding plate and rolled back in front of the expanding hot Tyrrhenian asthenospheric dome with the mobilisation of a viscous mantle material at depth. An active lithospheric fault is here imaged which cuts over more than 100 km into the Ionian basin. The fault runs from the Tyrrhenian margin in the SSE direction of Etna updip of the southwestern lateral edge of this slab, leaving north-eastward the extruded Calabrian block and on its south-westward edge the uplifted crust and mantle structures of Etna. Along it, the crust, including the Mesozoic and deeper layers, has sagged vertically in the segment in front of the slab, with a finite throw across the fault increasing from the basin towards Etna. © 2000 Elsevier Science B.V. All rights reserved.Funding was mainly provided by EC Environment Programme, Volcanic Hazard, under contract ETNASEIS EV5V-CJ92-0187 and EC JOULE Programme, under contracts STREAMERS (JOUG-CT90-0013) and PROFILES (JOU2-CT93-0313).Peer Reviewe