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158 G. Lavecchia et al. / Tectonophysics 445 (2007) 145–167

Fig. 9. Epicentral distribution of the events contained in the merged list of Table 1 and comparison with the SBT depth-contour lines. The dark grey
and light grey areas above the isobaths distinguish seismic zones situated above the upper crust and the mid-to-lower crust SBT portions, respectively;
the dotted area corresponds with the Agrigento–Licata aseismic zone.

central-southern Sicily. These events are highly debated macroseimic field as modelled by Gasperini et al. (1999)
from the seismotectonic point of view. and the northward deepening, from close to the surface
The 1968 Belice earthquake is the strongest event to to crustal depths, of the seismic sequence events with a
likely location of the main event at a depth of 13 km
have occurred in western Sicily in historical times (M aw
6.12, Working Group CPTI, 2004). It has been attributed (Anderson and Jackson, 1987; Monaco et al., 1996).
to either to N–S right lateral faulting along a lithospheric Still, it is coherent with the compressional kinematics on
transcurrent fault system, which would extend from the an E–W thrust plane of the neighbouring Mazara 1981
Sicily Channel to the southern Sicilian coast and would earthquake (M w 4.9). Last, but not least, there is no field
have allowed differential flexural retreat of the Pelagian evidence of N–S strike slip faulting in the epicentral
foreland (Cardamone et al., 1976; Gasparini et al., 1985; area, whereas evidence of fold-and-thrust activity in
Michetti et al., 1995; Meletti et al., 2000; Finetti and del Quaternary times has been observed (Monaco et al.,
Ben, 2005), or to reverse faulting along the E–W 1996). Considering all these arguments, the Belice event
striking Mt. San Calogero–Sciacca inner splay of the has been categorized as deep compressional event with-
SBT (Monaco et al., 1996; Valensise and Pantosti, in our merged dataset (Table 1).
2001). Both interpretations have the comfort of pub- The 1818 Catanese (M aw 6.0) earthquake is the
lished focal mechanisms that according to the Authors strongest event to have occurred in eastern central Sicily,
varies from strike–slip (Gasparini et al., 1985) to purely at the eastern Etna flank. There is a general consensus in
compressional (Anderson and Jackson, 1987). The considering it as a tectonic, crustal scale, event, not
reverse solution better fits the configuration of the associated to the Etna volcanic dynamics, but the likely