Behncke, Berrino and Velardita (2003) Ground deformation and gravity changes on the island of Pantelleria

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Boris Behncke, Giovanna Berrino and Rosanna Velardita (2003)
Ground deformation and gravity changes on the island of Pantelleria
in the geodynamic framework of the Sicily Channel
Abstract (invited paper) presented at the Annual Workshop 2003, Pantelleria, Sicily (23-28 September 2003)
on: Seismic Phenomena Associated With Volcanic Activity


Since the 1980's the island of Pantelleria has been periodically surveyed by means of geodetic and geophysical methods to monitor the regional and local volcanic dynamics. Horizontal and vertical ground movements and deformation are monitored through EDM, levelling and GPS. Additionally, high precision gravity measurements aimed to detect underground mass movements were started in 1990.
The results obtained by the analysis of the gravity data, collected during several field surveys carried out from 1990 to 1996, have shown that the gravity field changes generally appear composed by the superposition of short and long wavelengths, due to the combined effect of shallow and deep level sources. They also seem to reflect, to some degree, the structural setting of the island as sketched by the Bouguer anomaly field which indicates that the island is constituted by a basement dislocated in two main blocks. These latter are also bordered by two SE-NW and ENE-WSW trending lineaments, probably regional faults related to the global geodynamics of the Sicily Channel Rift Zone. A strong direct correlation between the gravity variation fields with the large-scale basement feature is apparent, mainly with the ENE-WSW lineation, visible along the Kaggiar-Cuddia Caffefi trend and corresponding to the limits between the two blocks.
Moreover, there is an inverse correlation between the gravity and altimetric variations. The joint analysis of gravity and elevation changes implies that Pantelleria appears to be divided in two blocks also from the kinematic behaviour.
In addition, comparison of the geological-structural setting of Pantelleria with that of the Sicily Channel, as outlined by geophysical and geological data, suggests that the observed phenomena may be also ascribed to the influence of the geodynamics of the Sicily Channel.
The present study is aimed at a comprehensive analysis of the time-space features of the horizontal ground deformation and gravity changes.
On the base of the previous conclusions we re-analysed all the EDM data collected on the island from 1976 to 1997, after which they were properly reorganized for comparison with gravity and altimetric data. This allows a joint interpretation taking also into account the structural setting and the geodynamics of the Sicily Channel to evaluate its influence on the local volcanic dynamics of the island.

Copyright © Boris Behncke, "Italy's Volcanoes: The Cradle of Volcanology"

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