GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 1.2 197 horizontal GPS velocity field, estimated using a multi-scale, spherical wavelets method (Tape et al. , 2009). The final vertical geodetic velocity field (Fig. 2) highlights several spatially consistent features, such as a relative vertical motion between the northeastern and southwestern sectors of the study area of ~1 mm/yr accommodated in a 30-40 km distance. This signal, of regional interest, shows a good agreement with GPS measurements (Fig. 2), mainly with those with longer time series whose vertical velocities are well constrained. It can be interpreted in terms of active tectonic deformation due to a deep compressional process, even if we cannot exclude the presence of other natural and/or anthropic processes (such as compaction of sediments and water pumping) that may affect the vertical signal. Due to the high InSAR data scattering in correspondence of more vegetated areas (central portions of the frame), we cannot clearly identify other velocity gradients referable to the ongoing tectonic extension. We made a preliminary attempt to apply a simple modeling approach that may reproduce the observed signal and we selected a sub-frame keeping the central part closest to the reference point, where the gradient is corroborated also by GPS data (sections 1-4 of Fig. 2). Moreover we subsampled the data considering only pixels with coherence value higher than 0.9. In order to invert the vertical InSAR data for position, dip and locking depth of a thrust fault below the eastern bound of this sector of Northern Apennines, we used a dislocation model (Savage, 1983). We observed that the fault geometry well reproduces the first order shape of the gradient, finding a good correlation with geological known structures (Barchi et al. , 1998; Lavecchia et al. , 2003) and with some of historical and instrumental seismic events located in this region (Rovida et al. , 2011). Fig. 2 – Vertical deformation rate extrapolated from InSAR data and compared with GPS vertical velocities along five cross sections.