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S250 Int J Earth Sci (Geol Rundsch) (2010) 99 (Suppl 1):S243–S264

Fig. 3 Compressional seismotectonic provinces (in grey) of central- central-right table reports some of the data used in the strain rate
eastern Italy and Sicily, with focal mechanisms and computed average calculation; the number of earthquakes for classes of magnitude is
tensor components. In the maps, which are located in Fig. 1, are also derived from Table 1 and the maximum observed magnitude
represented the Apennine and northern Sicily extensional seismotec- (M aw ± DM aw ) is derived from the CPTI04 catalogue (Working
tonic domains (rules) (after Lavecchia et al. 2007a). The focal group CPTI 2004a). In the lower-left inset, the average focal
mechanisms reported in the map are exclusively those falling within mechanism (moment tensor summation) of each province and the

the boundary of the compressional province and listed in Table 2. The related moment tensor F ij components are reported

catalogues, as well as from some specific papers (see Palermo and some surrounding localities (Azzaro et al.
Table 1 for the references). 2004), raising an obvious question about the attribution to
For the compilation of the earthquake–province asso- this province also of historical events sited along the
ciation datasets, we selected exclusively the historical and northern coast of Sicily. Following Azzaro et al. (2004)
instrumental events (Table 1), located within the province and Jenny et al. (2006), and on the basis of the ma-
boundary in the case of the Marche–Adriatic and main- croseismic data, we have attributed to the ST province the
land-southern Sicily areas. The choice of the historical earthquakes which hit Palermo in 1726 (M w 5.6), 1823
earthquake to be attributed to the Southern Tyrrhenian (M w 5.9) and 1940 (M w 5.4) (Working group CPTI
province has been much difficult. In fact, the earthquake 2004a). These events present very similar macroseis-
of 6 September 2002 (M w 5.6), located within the com- mic features to the 2002 event, and may therefore be
pressional Tyrrhenian strip about 45 km NE from Palermo ascribed to larger offshore seismic sources as stro-
at a depth range of *5–15 km, damaged the city of ngly supported by the distribution of the instrumental

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