Active upper crust deformation pattern along the southern edge of the Tyrrhenian subduction zone (NE Sicily): Insights from a multidisciplinary approach

Using a multidisciplinary dataset based on gravimetric, seismic, geodetic and geological observations,we provide
an improved picture of the shallow structure and dynamics of the southern edge of the Tyrrhenian subduction
zone.With a local earthquake tomographywe clearly identify twomain crustal domains in the upper 15 kmcharacterized
by different P-wave velocity values: a high-velocity domain comprising southeasternmost Tyrrhenian
Sea, NE Sicily and Messina Straits, and a low-velocity domain comprising Mt. Etna and eastern Sicily. The transition
between the two domains shows a good spatial correspondence with a wider set of faults including the
Taormina Fault System (TFS) and the Aeolian–Tindari–Letojanni Fault System (ATLFS), two nearly SE-striking
fault systems crossing northeastern Sicily and ending on the Ionian shoreline of Sicily according to many investigators.
Within this set of faults, most of the deformation/seismicity occurs along the northern and central segments
of ATLFS, compared to lowactivity along TFS. A lack of seismicity (both recent and historical) is observed in
the southern sector of ATLFS where, however, geodetic data reveal significant deformation. Ourmultidisciplinary
dataset including offshore observations suggests the southeastward continuation of the ATLFS into the Ionian Sea
until joiningwith the faults cutting the Ionian accretionarywedge described in the recent literature. Our findings
imply the existence of a highly segmented crustal shear zone extending from the Aeolian Islands to the Ionian
Abyssal plain, that we believe plays the role of accommodating differential motion between the Southern
Tyrrhenian unit and the western compressional domain of Sicily. The ATLFS, which is a main part of the inferred
shear zone, behaves similarly to what often observed at the edges of retreating subduction