The role of trench retreat on the geometry and stress regime in the subduction complexes of the Mediterranean

Numerical modelling of the Aegean and Calabrian subductions using geological reconstructions starting 75–80 Myr before the present reproduces the present-day geometries of the slabs and mantle wedges imaged by seismic tomography. The change from a shallow subduction dip of about 15° from the surface to a depth of 200 km into a dip of 60° below this depth in the Aegean subduction is caused by the south-west migration of the trench at the velocity of 3 cm/yr, obtained from GPS and geological data. The largest dip of 70° Calabrian subduction is caused by the termination of the active phase of opening of the Tyrrhenian back-arc basin and by the essentially purely gravitational sinking of the slab, in agreement with the null trench-migration velocity obtained from GPS data in Calabria. These two different tectonic settings are the ultimate causes of the different styles of seismicity within the two subduction complexes.