Local, regional, and plate scale sources for the stress field in the Adriatic and Periadriatic region

Abstract

The stress field at a specific location is the sum of regional stress, controlled by plate-scale tectonic processes, with local sources. Here we evaluate and discuss the different sources (from geodynamic to local scale) and the controlling factors (including the Jurassic paleogeography of the Adriatic passive margin) of present-day stress in the Adriatic Sea and Periadriatic regions of Italy using two kinds of numerical models: 3D mantle scale viscoelastic models and 2.5D lithosphere scale thin-shell models.The subcrustal stress field of the slabs in the Dinarides–Hellenic and Apennines–Calabrian subduction zones are characterized by downdip extension and compression, respectively. This difference is explained by the velocity of the Adriatic slab with respect to the upper mantle in the hotspot reference frame. The slab in the Calabrian subduction zone is encroached and down-pushed, whereas the slab in the Hellenic subduction zone is sustained by the mantle flow. At the plate scale, the upper crustal stress field at the Apennines front is governed by the different nature of the lithosphere (probably oceanic in the Ionian Sea and continental elsewhere), which in turn determines first-order rotations of the stress axes. Second order rotations of the stress axes depend on the Jurassic paleogeography and consequent differential advancement of the thrust fronts, with recesses and salient occurring in correspondence with Jurassic structural highs and lows respectively. The eastward relative motion of the mantle with respect of the lithosphere enhances the onset of NW–SE oriented compression within the Adriatic plate, consistent with observations. Finally, 2.5D thin-shell models demonstrate that present-day stress does not simply follow the long wavelength pattern (500–1000 km) due to plate tectonics and mantle interaction, but is greatly affected by the presence of second and third order sources, like crustal structure, faults and topography. Most importantly, these factors give an observable effect in data.