Modeling ground deformation associated with the destructive earthquakes occurring on Mt. Etna’s southeastern flank in 1984

The Timpe Fault System is the source of very shallow
but destructive earthquakes that affect several towns and
villages on the eastern flank of Mt. Etna (Italy). In 1984, several
seismic events, and specifically on 19 and 25 October,
caused one fatality, 12 injuries and produced serious damage
in the Zafferana and Acireale territories. This seismicity was
mainly related to the activity of the Fiandaca Fault, one of
the structures belonging to the Timpe Fault System.
We inverted ground deformation data collected by a
geodimeter trilateration network set up in 1977 at a low altitude
along the eastern side of the volcano in order to define
the Timpe Fault System faulting mechanisms linked to the
seismicity in 1984.
We have found that in the period May 1980–October 1984,
the Fiandaca Fault was affected by a strike-slip and normal
dip-slip of about 20.4 and 12.7 cm respectively. This
result is kinematically consistent with field observations of
the coseismic ground ruptures along the fault but it is notably
large compared to displacements estimated by seismicity,
then suggesting that most of the slip over the fault plane
was aseismic.
The results once again confirm how seismicity and its relation
with ground ruptures and creep displacement represent
a very high hazard to the several towns and villages situated
along the Timpe Fault System.