The contribution of InSAR analysis for the characterization of fault dynamics at Etna volcano (Italy): an application to microzonation studies

Mt. Etna is a complex and highly dynamic system, where tectonic structures, gravitational instability, and magmatic processes interact to produce heterogeneous deformation patterns, particularly along its eastern flank. This sector is affected by a network of active faults accommodating the seaward motion of the unstable flank and capable of producing shallow and damaging earthquakes, such as the Mw 5.0 Fiandaca event of 26 December 2018. Beyond the seismotectonic implications for seismic hazard, active faulting also has significant consequences for land management, since buildings and infrastructure located close to fault traces are particularly exposed to damage due to ground ruptures. Here we analyze the spatio‑temporal evolution of ground deformation using a DInSAR time‑series approach based on Sentinel‑1 data over the 2015‑2020 period. We focus on a fault‑oriented differential LOS analysis able to distinguish creeping, locked/seismogenic, and coseismically activated fault segments along Mt. Etna’s eastern flank. While both viewing geometries were processed to characterize the deformation field at the volcano scale, the differential fault‑slip investigation was developed, in this first application, on the ascending dataset. The results reveal a fault‑controlled deformation pattern marked by spatial discontinuities across the main tectonic structures, two distinct deformation phases before and after the December 2018 intrusive‑seismic event, and strong variability in fault behavior. By reducing the broader background deformation, the differential approach isolates the fault‑related component and highlights the coexistence of persistent creep, locked/seismogenic behavior, and coseismic activation along adjacent fault sectors. Overall, these findings confirm the effectiveness of DInSAR time‑series techniques for resolving fault kinematics in volcanic environments and provide support for the definition (extension and size) of Susceptibility and Respect Zones in Level 3 seismic microzonation applications at Mt. Etna.