The influence of erosional processes on the visibility of Permanent Scatterers Features from SAR remote sensing on Mount Etna (E Sicily)

• We analysed the interferograms based on SAR images of Mt. Etna.
• Permanent Scatterers Features following the main active faults have been recognised.
• The recognised PSFs form two distinct groups, according to their kinematics.
• Strike-slip faults are constantly visible, normal faults only appear episodically.
• The visibility of PSFs results from the combination of tectonic offset and erosion.

Analysis of 1549 DInSAR interferograms, covering the period from 2003 to 2010, has highlighted significant motion along the entire set of the active faults identified by advanced DInSAR analyses (i.e. Permanent Scatterers Features, PSF), affecting the Mount Etna volcano, in eastern Sicily. In the analysed period, the absence of significant seismicity producing co-seismic ground deformation suggests that the overall deformation that has been recognized on the interferograms is to be associated with interseismic, almost continuous creep which is, well documented along most of the active faults. According to field evidence, the structures should accumulate displacements resulting in their permanent visibility on the interferograms, progressively increases through time. This expected behaviour has been recognised only for part of the entire set of structures. Other tectonic features, in fact, show episodic appearances, alternating with periods of absence of ground displacement on the interferograms, simulating a stick-slip mechanism of deformation, conflicting with field evidence. This apparently incongruous behaviour can be interpreted as the result of topographic changes due to the combination of the tectonic displacements with related amounts of the differential erosion and deposition across the fault line. The comparison between the history of the appearances and the monthly rainfall in the region seems to demonstrate that these structures appear when one of the two interacting processes governing the topographic changes around the fault, i.e. tectonic vs. erosional, prevails over the other. Otherwise, the same structures are not evident on the interferograms when the two components are in balance.