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During the Mw 4.9 earthquake of December 26, 2018, an 8 km long arc‐shaped coseismic fracture belt formed along the southeastern flank of Etna Volcano (Sicily, Italy). We performed prompt field mapping of the 2018 coseismic fracture field, integrated with structural measurements in about 600 sites. The fracture belt comprises a northern, 3‐km‐long N130° striking segment, and a southern, 5‐km‐long N150°–170° portion. Along the former segment our data document a dextral shear zone, geometrically and kinematically coherent with the focal mechanism of the earthquake and indicating N170‐oriented compression. This shear zone shows a distinctive ground signature affecting lava flows of different ages, suggesting progressive growth of the structure through repeated coseismic cycles. The coseismic strain migrated to the NNW‐oriented segment, along which the strike‐slip deformation changed into N100–120°‐trending extension. The deformation along this segment is derived from the reactivation of a Late Quaternary tectonic boundary separating two adjacent compressional and extensional domains. The overall coseismic deformation is the result of these two different kinematics, consistent with the long‐term dynamics of both adjacent domains. The growth rate of recent cumulative morphotectonic features along the remobilized NNW‐striking fault demonstrates that the structure is still deforming at a rate comparable to the long‐period estimate. Our study points out that the 2018 seismic event, even if triggered by volcano‐tectonic processes, represents the expression of the composite regional dynamics, which are well constrained by large scale geodetic data. Key Points: The study is based on field mapping of the 2018 Mount Etna coseismic fracture field and on 600 structural in situ measurementsWe compared the kinematics along the composite coseismic fracture belt to the Late Quaternary regional kinematicsThe seismic event is coherent with the active dynamics at the regional scale [ABSTRACT FROM AUTHOR]

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. • The 2018 earthquake at Mt. Etna produced a very variable ground fracture belt. • Geometry and rank of the ground breaks vary with the near surface stratigraphy. • The ground fracturing was inhibited through thickened recent lava fields. • Widespread contractional deformation locally balanced the vertical fault restriction. [ABSTRACT FROM AUTHOR]

A geologic and geodetic integrated analysis of the northern margin of the Hyblean Plateau (SE Sicily) has been carried out in order to test the relationship between the active deformation, recorded by GPS data, and the long-term tectonic evolution, reconstructed by the interpretation of structural and morphological data. Our study revealed the active growth of a large antiform, as a consequence of the positive tectonic inversion of the previous flexure, bordering the Hyblean Foreland. The deformation of Middle–Late Pleistocene marine terraces and the evolution of the drainage system are consistent with a progressive regional tilting of the entire eastern sector of the Hyblean Plateau (Siracusa Domain), representing the southern limb of the active antiform. The geometry of the Late Quaternary marine strandlines, compared with the results of analogue models, is compatible with the effects of the NW-ward propagation of a detachment fault at depth. The active deformation of the Hyblean region, coherent with the Nubia–Eurasia plate convergence, suggests to candidate the inverted tectonics at the northern border of the Hyblean Plateau as potential seismogenic sources of the area. [ABSTRACT FROM AUTHOR]