Crustal deformation of a sector of the southern Alps adjacent to the Po plain (Northern Italy): an integrated study.

The zone of deformation of the central-eastern Southern Alps and their adjacent Po plain sector (Giudicarie sensu lato) represents the tectonic divide between the Central and the Eastern Alps. Its role in accommodating crustal scale deformation was investigated, through the analysis of the effects of past (pseudotachylytes) and present-day (earthquakes) deformations, and thermal/rheological modelling. The Palaeogene-Neogene tectonic activity of the Tonale nappe, pertaining to the Giudicarie fault system in the internal Alpine chain, is testified by both ductile (mylonites) and brittle (pseudotachylytes) indicators. The present-day seismotectonic activity of the Giudicarie-Lessini region (Southern Alps) was highlighted by seismicity, focal mechanisms, and directions of principal stress and strain axes. In this region a significant change of kinematic regimes and maximum horizontal compressive stress directions is observed (seismotectonic zones G and L). The crust thermal/rheological setting of the Po plain sector adjacent to the Giudicarie-Lessini region was characterized for two different contiguous domains (zones W and E). The crustal thickness of the western domain is hotter (modelled temperature) and less resistant (calculated total strength of the crust) than the eastern domain. Different-type geological-geophysical results demonstrate the presence of the still active Giudicarie sensu lato tectonic divide, which may be interpreted also in the light of active deformation along the Eastern Alps and the Northern Apennines.