Interseismic deformation in the central-southern Apennine

The GPS results are of utmost relevance for the study of the complex plate boundary geodynamics. The lithosphere strain partitioning is part of the seismic cycle. We present the first GPS kinematic pattern obtained during the interseismic phase by a dense episodic GPS network, the Southern Apennine Geodetic Network (SAGNet), in the time span 2002-2013. This network is located across the transition zone between central and southern Apennine, including Meta-Mainarde-Venafro and Alto Molise-Sannio-Matese mounts. This region is one of the most seismic areas of Italy characterized by seismogenic faults systems responsible, in the past, for several destructive earthquakes of intensity I ≥ IX MCS and, in more recent years, characterised mainly by some lower magnitude seismic sequences (max magnitude Ml 4.9, December 29 2013) and single small events (Ml < 2.5). The GPS velocity field, obtained by combining data from (i) SAGNet network, (ii) continuous GPS stations and (iii) data of other episodic networks, shows a perpendicular maximum extension with respect to the Apennine chain of about 2.5 mm/yr. The strain rate field, estimated before the December 29, 2013 Ml 4.9 earthquake, shows in the epicentral area a lower value with respect to the surroundings. The results obtained indicate that the active deformation is controlled by the relative kinematic between Eurasia and Adria plates. We conclude that the active deformation is spreading in a narrow belt bordering the eastward flank of the Apennine chain.