IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4W_2C-P11

Date/Time: July 24 Poster

The Pernicana and Trecastagni faults: the most active structures dissecting Mt. Etna
volcano (Sicily) studied by multidisciplinary ground deformation measurements
Alessandro Bonforte1 , Gianpiero Aiesi1 , Giuseppe Brandi2 , Francesco Calvagna1 , Salvatore Consoli1 ,Giuseppe Falzone1 , Angelo Ferro1 , Salvatore Gambino1 , Francesco Guglielmino1 , Giueppe Laudani1 ,Francesco Obrizzo2 , Giuseppe Puglisi1 , Benedetto Saraceno1
1Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, Italy, 2 Istituto Nazionale diGeofisica e Vulcanologia, Osservatorio Vesuviano, Italy
E-mail: alessandro.bonforte@ct.ingv.it

The complex interaction between regional stress, gravity forces and dike-induced rifting, seems to have a role in
the eastward movement of the Mt. Etna eastern flank. In this context the Pernicana and the Trecastagni-Tremestieri
Fault systems seem to identify the northern and southern boundaries of the unstable sector.
The Pernicana fault system forms a left-lateral shear zone that dissects the north-eastern flank of Etna. The
kinematics of this system is related to shallow seismic crises (M ≈ 4.0) occurring along the western segment. The
eastern segment, ESE trending, is only affected by aseismic creep with purely left-lateral displacement.
The Trecastagni fault is a NNW-SSE tectonic structure on the lower southern flank, characterized by evident
morphological scarps and normal and right-lateral movements damaging roads and buildings. This fault is affectedby continuous dynamics with episodic accelerations accompanied with shallow seismicity.
The dynamics of these faults has been analysed by a multi-disciplinary approach with terrestrial (levelling acrossboth faults and extensometers record on the Trecastagni fault) and satellite (InSAR data and GPS surveys) grounddeformation data.
The levelling route on Mt Etna is 150 km long and consists of 200 benchmarks. Part of the levelling route crosses
the Pernicana fault, at an altitude of 1400 m asl. A new levelling network has been installed across the Trecastagni
fault and it showed a mean vertical slip rate of about 1 cm/y and episodic acceleration on short segments of thefault, with displacements of almost 3 cm.
The monitoring of the Trecastagni fault is also performed by two continuous wire extensometers and a system forperiodic direct measurements across the fault in its central and north-central sectors. The two stations measure
the relative displacements perpendicular to the fracture, evidencing an opening of about 2-3 mm/y.
Both faults show clear traces on SAR interferograms and time series. InSAR data allows tracking the path of thePernicana fault with a rate of about 2-3 cm/y. The Trecastagni fault shows a main vertical kinematics, at a rate ofabout 4 mm/y, with a minor E-W component.
The dense GPS network is measured periodically and has more than seventy benchmarks. Two GPS sub-networks
lie across the eastern segment of the Pernicana fault. The first one was installed in April 1997; the second one
was measured for the first time in July 2002 upgrading an EDM network. The aim of these networks is to detail thestructural framework and displacements along the aseismic sector of the fault.
Integration of this wide spectrum of geodetic data allows strongly constrained ground deformation pattern to bedefined and modeled. Furthermore, the very long time series available on the Pernicana fault, allows its behavior
to be investigated in time and its role and relationships in the framework of flank instability and eruptive activity tobetter understood.

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