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 mech anisms under investigation are subduction of the Ionian oceanic lithosphere beneath the Calabrian are and continental convergence between the African and Eurasian blocks. Very Long Baseline Interferometry (VLBI) data at the s tation Note in Sicily and the results from global models of plate motions a re taken as representative of the motion of the African plate with respect to Eurasia, while VLBI solutions at Matera and Medicina, in the southern an d northern parts of the Italian peninsula, are geodetic observations that m ust be compared with modelling results. Vertical deformation rates are take n from geological and tide gauge records. The model that best fits the obse rvations 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 Tyrr henian domain, in agreement with VLBI data from the Matera and Medicina sta tions and GPS data from northeastern Sicily and the Eolian Islands. The hig hest subsidence rates are obtained in the southern Tyrrhenian, and are of t he order of 1.2-1.4 mm yr(-1). Along the whole Adriatic coast of the Italia n 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 are is responsible for a rollback vel ocity higher than in the northern areas. 2-D models, built for the geologic al past, indicate the possibility of roll-back velocities of several centim etres per year. In particular, active rifting in the Tyrrhenian and softeni ng of the crust in the back-are basin result in a trench retreat velocity i n agreement with geological estimates. Our results show that numerical mode lling can be used to estimate present-day deformation rates and the contrib ution of active tectonics to sea-level changes along coastal areas.