Three-dimensional modelling of crustal motions caused by subduction and continental convergence in the central mediterranean

Crustal deformation in the central mediterranean is modelled by means of 3-D finite element models assuming a viscoelastic rheology. The tectonic mechanisms under investigation are subduction of the Ionian oceanic lithosphere beneath the Calabrian arc and continental convergence between the African and Eurasian blocks. Very Long Baseline Interferometry (VLBI) data at the station Noto in Sicily and the results from global models of plate motions are taken as representative of the motion of the African plate with respect to Eurasia, while VLBI solutions at Matera and Medicina, in the southern and northern parts of the Italian peninsula, are geodetic observations that must be compared with modelling results. Vertical deformation rates are taken from geological and tide gauge records. The model that best fits the observations includes the effects of subduction in the southern Tyrrhenian and convergence between Africa and Europe. The overthrusting of the Tyrrhenian domain onto the Adriatic domain results in an eastward component of the velocity at the eastern border of the Tyrrhenian domain, in agreement with VLBI data from the Matera and Medicina stations and GPS data from northeastern Sicily and the Eolian Islands. The highest subsidence rates are obtained in the southern Tyrrhenian, and are of the order of 1.2-1.4 mm yr^-1. Along the whole Adriatic coast of the Italian peninsula, subsidence in the foredeeps is of the order of 0.2-0.5 mm yr^-1. The Apenninic chain is rising with rates of the order of 0.2-0.4 mm yr^-1. Subduction beneath the Calabrian arc is responsible for a rollback velocity higher than in the northern areas. 2-D models, built for the geological past, indicate the possibility of roll-back velocities of several centimeters per year. In particular, active rifting in the Tyrrhenian and softening of the crust in the back-arc basin result in a trench retreat velocity in agreement with geological estimates. Our results show that numerical modelling can be used to estimate present-day deformation rates and the contribution of active tectonics to sea-level changes along coastal areas.