The interseismic velocity field of the Central Apennine from a dense GPS network

Since 1999 we have repeatedly surveyed the Central Apennines by means of a dense survey style geodetic network (CAGeoNet) consisting in 123 benchmarks distributed in an area of ~180 x 130 km extended from the Tyrrhenian Sea to the Adriatic Sea with an average inter-site distance of 3-5 km. The network is located across the main seismogenic structures of the region, able to generate destructive earthquakes. Here we show the horizontal GPS velocity field of the CaGeoNet and the available continuous GPS (CGPS) stations in this region, that are estimated from their position time series in the time span 1999-2007. Data have been analyzed using Bernese and Gamit software and the two solutions have been rigorously combined to minimize software-dependent systematic errors. We analyze the strain rate field, which shows a region characterized by extension located along the axis of the Apennines chain, with values ranging from 2 to 66 10-9 yr-1 and a relative minimum of 20 10-9 yr-1 located in the L’Aquila basin area. Our velocity field represents an improved estimation of the ongoing elastic inter-seismic deformation of central Apennines in particular of the L’Aquila earthquake of April 6th, 2009 area.