The effect of recent resurfacing in volcanic areas on the distribution of co-seismic ground deformation due to strike-slip earthquakes: New insights from the 12/26/2018 seismic event at Mt. Etna

We analyzed the dispersion of the co-seismic fracturing due to the December 26, 2018 event at Mt. Etna (Italy) along the deformation belt matching the seismogenic source at depth. Our study, based on measurement of 390 ground fractures, reconstructed the variability of the geometry and the changes in the rank (length and displacement) of the ground breaks, through different compound lava fields. The study evidenced that the narrow capable dextral fault zone emerges where ancient lavas crop out or are draped by a thin layer of younger lava flows. Conversely, within recent compound lava fields, consisting of multiple superimposed flow units, the main mechanical anisotropy within the near-surface layers inhibited the along-dip fault propagation. The vertical restriction of the fault propagation produced a spread ground deformation, responding to the motion along the blind main fault. Our results provide a significant example how the laterally changing near-surface stratigraphy of an active volcano edifice can influence the ground effects due to the co-seismic displacement along strike-slip active fault. This evidence could represent new insights to be considered in predicting the susceptibility zone around active transcurrent faults in volcanic settings, prone to instabilities for future seismic events.