Fault creep and kinematics of the eastern segment of the Pernicana FaultMt.Etna,Italy)derivedfromgeodeticobservationsandtheir tectonic signi®cance R. Azzaro a, * , M. Mattia a , G. Puglisi b a Istituto Nazionale di Geo®sica Ð Sistema Poseidon, via Monti Rossi 12, 95030 Nicolosi CT), Italy b Istituto Internazionale di Vulcanologia Ð CNR, Piazza Roma 2, 95123 Catania, Italy Received 13 July 2000; accepted 22 January 2001 Abstract Aseismic fault displacements related to numerous fast-slipping active faults are frequently observed on Mt. Etna, but the characteristicsandtherateofdisplacements,alongwiththebehaviourofindividualfaultsegments,arepoorlyconstrained.To resolvethis,weinstalledtwolocalgeodeticnetworksin1997alongtheeasternsegmentofthePernicanaFault,oneofthemost active structures in the geodynamic framework of the volcano. The networks are based on the electroptical distance measure- ments EDM) and global positioning system GPS) techniques and consist of four and six benchmarks, respectively. Geodetic data con®rm that the tectonic activity of the eastern Pernicana Fault is controlled by fault creep, i.e. a near- continuous stable sliding at a mean slip-rate of 2.8 cm/yr punctuated by aseismic displacement episodes. The analysis of the strain tensor calculated from the EDM and GPS data indicates that deformation in the fault zone is related to a clear sinistral strike-slipmovement.AmorecompletepictureisobtainedfromtheGPSmeasurementsfortheRoccaCampanaarea,wherethe mainstructurebranchesouteastwardintoasplayfault.Theinversionof3Ddisplacementvectorssuggestsadeformationmodel consisting of two principal sinistral strike-slip faults with an oblique component of movement. The maximum observed displacement, 6.1 cm measured in the period April 1997±February 1999, is accommodated by the splay fault. This ®nding corroborates the hypothesis that, as proposed by the tectonic models in the literature, the movement of the eastern segment of the Pernicana Fault is transferred easterly towards structures at a lower altitude along the same strike e.g. the Fiumefreddo Fault). As a consequence, the Pernicana Fault may constitute part of a continuous left-lateral trans-current zone, which displaces the whole north-eastern ¯ank of Mt. Etna. q 2001 Elsevier Science B.V. All rights reserved. Keywords: active faulting; creeping; geodetic measurements; deformation model; Pernicana Fault; Mt. Etna 1. Introduction The Pernicana Fault is one of the most active tectonic structures in the Etna area. Its geometry, kinematics and the exceptionally high slip-rate, suggest that it may play a key role in controlling the instabilityofthevolcano'seastern¯ank,andprobably represents the northern boundary of the unstable sectorFig.1a).Theseawardmovementofthevolcanic edi®ce has been interpreted as being gravity-driven Neri et al., 1991; Borgia et al., 1992; Lo Giudice and Rasa Á,1992)orduetodyke-inducedriftingMcGuireet al., 1996; Rust and Neri, 1996). In the latter case, the Pernicana Fault could also account for the extension inducedbymagmaintrusionintotheNEriftzone. Tectonophysics 333 2001) 401±415 0040-1951/01/$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII:S0040-195101)00021-X www.elsevier.com/locate/tecto * Corresponding author. E-mail address: azzaro@poseidon.nti.it R. Azzaro).