New insights in the geodynamics of the Lipari-Vulcano area (Aeolian Archipelago, southern Italy) from geological, geodetic and seismological data

Geological, geodetic and seismological data have been analyzed in order to frame the Lipari-Vulcano complex (Aeolian archipelago, southern Italy) into the geodynamic context of the southeastern Tyrrhenian Sea. It is located at the northern end of a major NNW-SSE trending right-lateral strike-slip fault system named “Aeolian-Tindari-Letojanni” which has been interpreted as a lithospheric discontinuity extending from the Aeolian Islands to the Ionian coast of Sicily and separating two different tectonic domains: a contractional one to the west and an extensional one to the north-east. Structural field data consist of structural measurements performed on well-exposed fault planes and fractures. The mesostructures are mostly represented by NW-SE striking normal faults with a dextral-oblique component of motion. Minor structures are represented by N-S oriented joints and tension gashes widespread over the whole analyzed area and particularly along fumarolized sectors. The analyzed seismological dataset (from 1994 to 2013) is based on earthquakes with magnitude ranging between 1.0 and 4.8. The hypocenter distribution depicts two major alignments corresponding to the NNW-SSE trending Aeolian-Tindari-Letojanni fault system and to the WNW-ESE oriented Sisifo-Alicudi fault system. GPS data analysis displays ∼3.0 mm/yr of active shortening between the two islands, with a maximum shortening rate of about 1.0 × 10−13 s−1, between La Fossa Caldera and south of Vulcanello. This region is bounded to the north by an area where the maximum values of shear strain rates, of about 0.7 × 10−13 s−1 are observed. This major change occurs in the area south of Vulcanello that is also characterized by a transition in the way of the vertical axis rotation. Moreover, both the islands show a clear subsidence process, as suggested by negative vertical velocities of all GPS stations which exhibit a decrease from about −15 to −7 mm/yr from north to south. New data suggest that the current kinematics of the Lipari-Vulcano complex can be framed in the tectonic context of the eastward migrating Sisifo-Alicudi fault system. This is dominated by transpressive tectonics in which contractional and minor extensional structures can coexist with strike-slip motion.