Mechanically Consistent Model of the 2018 Christmas Volcano‐Tectonic Event at Etna.

The interaction between volcanic activity and flank instability during the Christmas Eve eruption at Mount Etna in 2018 is explored, using a mechanically consistent inverse model fitting high spatial resolution SAR data. Inversions search for fractures that may be curved and can accommodate co‐eval pressure and shear stress changes. Displacements associated with the eruption result from the interaction between two intrusion sources: a buried dyke and a curved sheared intrusion that fed the eruption. Moreover, we identify that the sheared magmatic intrusion induced the observed eastward slip on the Pernicana fault, while the Fiandaca fault was undergoing stress accumulation, which was suddenly released during a M5.0 seismic event. The Fiandaca fault is determined to be listric, rooting beneath the mobile eastern flank of the volcano. This study highlights the role of curved fractures, acting as sheared intrusions or as faults, in volcanoes exhibiting flank instabilities. Plain Language Summary: In this study, we thoroughly examine how volcanic activity and flank dynamics interacted during the 2018 eruption of Mount Etna. We use high‐resolution satellite SAR data and a model considering complex mechanical aspects of the volcano's behavior. Formal inversions reveal that the eruption is triggered by the interplay between two intrusion sources: a buried dyke and a curved sheared intrusion, consistent with the earthquake pattern. This study emphasizes the significant role of curved sheared intrusions and faults at volcanoes prone to flank instabilities. Furthermore, we quantify how summit magmatic intrusions promote fault slip in the eastern flank of Etna. These findings differ from previous research that used simpler approaches. In summary, our study provides a new insight into how volcanoes like Etna can erupt and trigger flank slip, shedding light on the complex interactions between magma and tectonics. Key Points: Modeling shows that the magma intrusion feeding the 2018 eruption accommodated coeval opening and shear displacementsBoth the summit intrusions and the Fiandaca fault are curved, probably connected to the detachment at the base of the mobile eastern sectorThe Fiandaca fault was previously locked. It released accumulated stress, while the Pernicana fault passively responded to the intrusion [ABSTRACT FROM AUTHOR]