GPS mesurements of active strains across the Apennines (Italy)

Abstract Geodetic data are providing a new prospective in studying active tectonic processes that are occurring in peninsular Italy. In this paper we use a recently published GPS velocity solution, obtained by merging a data set of permanent and non-permanent networks spanning the 1991-2002 time interval, to provide new quantitative constraints of the active deformation rates across the Apennine chain and the Calabrian Arc. The velocity field, given with respect to a fixed Eurasian frame, has been used to compute horizontal strain-rates within polygonal regions that connect and include geodetic stations and to draw velocity cross sections along 5 different profiles through this region. The computed strain-rates provide a picture of the regional deformation field, which is in agreement with other seismological and geological data, and show that the Apennines are mainly extending in a SW-NE direction, while in Calabria extension is NW-SE oriented. Only in the outer Northern Apennines indications of active shortening are present. The velocity profiles, constructed across the Northern and Southern Apennines and along the Tyrrhenian Sea across Calabria, provide a quantitative measurement of the active extension and shortening rates, which are taking up at a more local scale