Dyke intrusion, earthquake and flank collapse at Mt. Etna: co- and post- 2018 events deformation from multisensor InSAR and CGPS

In the last decades, a number of studies have pointed out how the pressurization of magmatic bodies and/or magmatic intrusions through the shallow crust influences local stress promoting fault slip within or close to volcanic edifices. Similarly, inherited tectonic structures might impact on inhomogeneous long-term updoming, complex asymmetric topography and flank instability, as suggested for Mt. Etna volcano. Here, we focus on the shallow dyke intrusion occurred on 24^th December 2018 beneath the summit area as well as a seismic swarm (Mmax=4.9) striking the south-eastern flank of the volcano. Exhaustive multisensor SAR interferometry and continuous GPS measure the 2018 Dec. co- and post-intrusive deformation. By inverting the displacement dataset, we model i) a shallow dyke intrusion correlating with deep faults cutting through the sedimentary basement below the volcanic edifice, observed in tomographic model, ii) a fault plane activated on 26^th December 2018. Moreover, flank collapse occurs at volcanic-sedimentary interface where the stress strongly increases due to the dyke intrusion. Mutual interaction between intrusions and collapse promotes a feedback process favoring the fault activation along the unstable flank edges and the long term refeeding of the deep plumbing system.