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From Gibraltar to Anatolia, the active tectonics in the Mediterranean is studied by means of an integrated approach based on geophysical, geodetic, and seismological methodologies. The aim of this study is to gain a deep insight into the kinematics and dynamics of the crustal and lithospheric processes affecting the Mediterranean. Major tectonic processes, such as continental collision and subduction, characterize this region, which marks a broad transition zone between the African/Arabian and Eurasian plates. A thin-shell finite element approach allows us to simulate the deformation pattern in the Mediterranean, from 10°W to 40°E and from 30° to 50°N. The global plate motion model NUVEL-1A is used to account for the convergence, while the relative velocities of the overriding and subduction plates are obtained from another family of models. These models simulate the effects of the negatively buoyant density contrasts of the subducted lithosphere on the horizontal velocity at the surface. A systematic comparison between model results and the seismic strain rates obtained from the National Earthquake Information Center catalog, the geodetic velocity field and strain resulting from GPS, satellite laser ranging, and very long baseline interferometry analyses and the World Stress Map, indicate that Africa/Arabia versus Eurasia convergence and subduction in the Aegean Sea and Calabrian Arc are the major tectonic mechanisms controlling the deformation style in the Mediterranean. It is shown that in order to carry into coincidence the modeled and the seismic strain rate patterns and the geodetically retrieved strain rate tensors, a deep subduction in the Aegean Arc must be included in the modeling., This work is supported by the COFIN2000 project of the Italian Ministry of the Instruction, University and Research, “Active deformation at the northern boundary of Adria.” This has also been supported by the contract ASI-1998-2000-Working group on measurements and methods of high precision Space Geodesy.

The geodetic velocity and strain rate patterns in Anatolia constrain the rheology of the lithosphere, once compared with thin shell finite element tectonic model predictions. Geodetic and modeled deformation favors a hard lithospheric rheology, responsible for the high East-West horizontal velocities in the center of Anatolia, between 39°–41°N, in proximity of the North Anatolian Fault. The block like behavior of Anatolia, due to the hard lithospheric rheology, is responsible for the low geodetic and modeled strain rates in the center of the peninsula. The low strain rate is well correlated with the region of low release of seismic energy between 33°–36°E and 38°–40°N. The high seismic and geodetic strain rate region in the far west part of the NAF is also well reproduced by the modeling., This work is supported by the COFIN2000 project of M.I.U.R “Active deformation at the northern boundary of Adria”. Peter Bird is thanked for the finite element SHELLS program.

Recent investigations from laboratory and Monte-Carlo inversion of geophysical signatures have suggested that the transition zone of the mantle between 400 and 670 km depth may be stiffer than the lower and the upper mantle. By means of a five-layer viscoelastic spherical Earth model, we have calculated the displacement fields associated with post-glacial rebound, the induced polar motions, the temporal variations of the coefficients of the geopotential up to degree eight and the stress fields induced by deglaciation in the lithosphere and the upper mantle. Temporal variations of stress fields in the lithosphere reveal a non-monotonic behaviour due to the viscosity stratification. The results demonstrate the importance of the coming LAGEOS II geodetic satellite mission on constraining the rheological nature of the transition zone in the mantle. -from Authors

cited By 0; By means of a stratified Earth model with viscoelastic rheology, we have studied the long-term global fluctuations of Relative Sea Level (RSL) induced by subducting slabs. We have computed RSL variations for both a single subduction and a realistic distribution of slabs by a numerical simulation based on a simplified model of the subduction process. RSL is determined by the offset between the geoid and the dynamic topography; our analysis demonstrates that the latter provides the prevailing contribution. We have studied, in addition, the effects of rheological stratification upon the amplitude and time-evolution of these two quantities and, consequently, of RSL fluctuations. According to our results, an upper bound for the rate of RSL associated with subduction is of the order of 0.1 mm/yr, in agreement with previous studies. This rate of sea level variation is comparable with that attributed to changes in the tectonic regime on a large scale. This preliminary result corroborates the suggestion by other authors to include subduction in the list of geophysical mechanisms which contribute to long-term RSL fluctuations.