Three-dimensional numerical modeling of contemporary mantle flow and tectonic stress beneath the Central Mediterranean

The structure, density and effective viscosity of the crust and uppermost mantle beneath the Central Mediterranean influence lithospheric deformation, mantle flow, and tectonic stress state. To estimate the contribution of buoyancy forces to regional dynamics, three-dimensional finite-element models are devel- oped to determine contemporary uppermost mantle flow and tectonic stresses. We use density models for the crust and uppermost mantle derived from S-wave seismic velocities and constrained by gravity data. The viscosity model is constrained by the observed strain rate and regional heat flow data. The modeled movement of the uppermost crust is consistent with the northeast-oriented motion of the lithosphere and is in an agreement with the geodetic measurements. The modeled flow patterns of the lower crust and uppermost mantle are consistent with the regional observations. The models predict (i) northwest-oriented movements beneath the southeast part of the Adriatic Sea region, (ii) the northeastern subduction beneath the western part of the Adriatic Sea, (iii) the upwelling beneath the Tyrrhenian Sea and its eastern coast, (iv) the western movement of the Ionian Sea sub-plate, and (v) the subduction beneath the western Calabria region. Our models predict also a distinct compressional regime along the northeast part of the Italian peninsula and to the east of Sicily, and a tensional regime beneath the Tyrrhenian Sea, Umbria–Marche region, and Ionian Sea. The predicted tectonic stress regimes in the northern and central Apennines are in agreement with stress regimes derived from earthquake fault-plane solutions. Changes in the predicted crustal stress pattern and magnitude are likely to be caused by buoyancy-driven mantle circulation beneath the region rather than by gravitational potential energy differences in the crust itself. Based on the model results, we conclude that the buoyancy forces play an important role in the contemporary tectonics of the region.