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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
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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.
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