Advanced InSAR and GPS measurements for the detection of surface movements along the Alto Tiberina (Italy) normal fault system: data modeling and future perspectives

Abstract:

The Alto Tiberina fault (ATF) is a low-angle (east-dipping at 15°), 70 km long normal fault (LANF) located in the Umbria-Marche Apennines (central Italy), an area characterized by a SW-NE oriented extension occurring at rates of ~2 mm/yr. Active extension is precisely measured by a dense distribution of GPS stations belonging to several networks, thanks also to additional sites recently installed in the framework of the INGV national RING network and of the ATF observatory. Advanced Interferometry SAR (A-InSAR) techniques play today a key role in Earth Sciences thanks to their capability to detect and monitor slow surface movements over wide areas. A-InSAR techniques, along with in-situ ground measurements, can provide suitable information on the causes of interseismic (seismic, creep) movements. Large datasets of SAR images of European (ERS 1-2 and ENVISAT) and Italian (COSMO-SKyMed) satellites have been used to retrieve surface velocity maps and relevant time series from 1992 to 2014, along both ascending and descending orbits. A network of artificial Corner Reflectors has also been deployed in the proximity of some GPS sites in order to calibrate the processing results of the COSMO-SkyMed SAR data-set and to derive velocity maps.

We use an elastic Block Modeling (BM) approach in order to model GPS data by considering the major fault systems as bounds of rotating blocks, while estimating geodetic fault slip-rates.,Thanks to the latest imaging of its deep structure obtained from seismic profiles, the ATF is represented as a complex rough surface with the goal of evaluating the distribution of interseismic fault coupling. The preliminary results obtained show firstly that the observed extension is partially accommodated by interseismic deformation on the ATF, highlighting the important role of this LANF inside an active tectonic contest. Secondarily, using the ATF surface “topography”, we found for the resolved areas an interesting correlation between microseismicity and creeping portions of the ATF.

Thus we integrate A-InSAR results and GPS velocities in order to use such data within a BM approach, with the aim that the availability of high-resolution data will contribute to understand better the behavior of this LANF and to evaluate the seismic potential associated to this geologic structure.