Page 20 - LaVecchia_Ferrarini_alii_2007

G. Lavecchia et al. / Tectonophysics 445 (2007) 145–167 163

structure, which extends from west to east across the Escarpment (Camassi and Stucchi, 1997; Azzaro and
entire Sicilian island, allows us to attribute in a simple Barbano, 2000; Monaco and Tortorici, 2000) and, finally,
way all the mainland and central-southern Sicily major to compression at the outer front of the Calabrian thrust
earthquakes (moment magnitude ≥ 4.5) to one single belt, along the offshore Ionian segment (Gutscher et al.,
regional seismogenic source. The definition of such 2006). We suggest to also consider the likelihood of an
large seismotectonic province, which has a total surface association of the 1693 earthquake with the offshore
2
extent of nearly 16,000 km , may be useful for seismic prosecution of the same SBT segment which was struck
hazard purposes as it overcomes the intrinsic problems by the 1818 Catania event. This alternative working hy-
in the location and magnitude estimation of historical pothesis is at the moment extremely preliminary and
earthquakes, that do not have to be so bound, and at the further research on this topic is required.
same time helps to individuate potentially seismic areas
also in the absence of historical and instrumental record. Acknowledgments
During the last 400 years, a lower level of seismic
activity and of energy release has characterized the We wish to thank Paolo Boncio, Bruno Pace,
shallow SBT compared to the deep SBT, with an almost Giuliano Milana, Salvatore Barba, Laura Peruzza and
total lack of historical and instrumental seismicity in the Pierpaolo Guarnieri for useful, friendly and stimulating
Agrigento–Licata central zone (dotted area in Fig. 9). discussions at different stages of the paper. Two
Available data do not permit us to infer if this deficit, anonymous reviewers and the editor Mike Sandiford
which is the equivalent of a magnitude 6 event, might be are kindly acknowledged for their critical reading of the
due to aseismic slip along a very flat portion of the SBT, manuscript and for their valuable suggestions. The work
to historical catalogue incompleteness and/or to longer was supported by Ud' A grants to G.L.
recurrence times. We also cannot exclude that the 361
Central Sicily earthquake (M aw 6.6) might have nucleated References
within the shallow sub-province. Evidently, these doubts,
which had not been considered in the previous literature,
Amodio-Morelli, L., Bonari, G., Colonna, V., Dietrich, D., Giunta, G.,
may have strong implication in terms of seismic hazard Ippolito, F., Liguori, V., Lorenzoni, S., Paglionico, A., Perrone, V.,
assessment. We must not forget that also the Belice Piccareta, G., Russo, M., Scandone, P., Zanettin-Lorenzoni, E.,
earthquake arrived completely unexpected and we should Zuppetta, A., 1976. L'arco Calabro–Peloritano nell'orogene
not make the same error again. Appenninico–Maghrebide. Boll. Soc. Geol. Ital. 17, 1–60.
Anderson, H., Jackson, J., 1987. Active tectonics of the Adriatic
In conclusion, although the geology of Sicily is espe-
region. Geophys. J. R. Astron. Soc. 91, 937–983.
cially complicated and the quality of available instru- Argnani, A., 1987. The Gela Nappe: evidence of accretionary mélange
mental data is not favoured by the configuration of an in the Maghrebian foredeep of Sicily. Mem. Soc. Geol. Ital. 38,
island seismic network, the joint interpretation of data 419–428.
from different sources, together with the analysis of a Azzaro, R., 1999. Earthquake surface faulting at Mount Etna volcano
(Sicily) and implications for active tectonics. J. Geod. 28, 193–213.
seismological updated merged (historical and instru-
Azzaro, R., Barbano, M.S., 1997. Intensity–magnitude relationship for
mental) dataset of all the known major (moment mag- the Mt. Etna area (Sicily). Acta Vulcanol. 9 (1/2), 15–21.
nitude ≥ 4.5) earthquakes occurring in the study area Azzaro, R., Barbano, M.S., 2000. Analysis of seismicity of
nearly in the last 2000 years (Table 1), has allowed to Southeastern Sicily: proposal of a tectonic interpretation. Ann.
build a well constrained and coherent picture and to assign Geofis. 43, 171–188.
Azzaro, R., Barbano, M.S., Antichi, B., Rigano, R., 2000a.
a fundamental role to the crust-scale thrust tectonics in the
Macroseismic catalogue of Mt. Etna earthquakes from 1832 to
seismogenesis of the region. Furthermore, the identifica- 1998. Acta Vulcanol. 12, 3–36 and CDROM.
tion of a new regional seismogenic source, the SBT, might Azzaro, R., Barbano, M.S., Rigano, R., Antichi, B., 2000b. Contributo
offer new key-interpretation to still debated events such as alla revisione delle zone sismogenetiche della Sicilia. In: Galadini,
the highly destructive and tsunamogenic 1693 eastern F., Meletti, C., Rebez, A. (Eds.), Le ricerche del GNDT nel campo
della pericolosità sismica (1996–99). CNR-Gruppo Nazionale per
Sicily earthquake (I 0 XI MCS scale) (see upper left inset in
la Difesa Terremoti, Roma, pp. 31–38.
Fig. 10). The event, whose isoseismal are open seawards Baratta, M., 1897. Materiali per un catalogo dei fenomeni sismici
(Piatanesi and Tinti, 1998; Azzaro and Barbano, 2000; avvenuti in Italia (1800–1872). Mem. Soc. Geogr. Ital. VII, 81–164.
Gutscher et al., 2006), has been associated to SW–NE Barbano, M.S., Rigano, R., 2001. Earthquake sources and seismic
striking blind normal fault along the Lentini graben hazard in South-eastern Sicily. Ann. Geofis. 44, 723–738.
Bello, M., Franchino, A., Merlini, S., 2000. Structural model of
(D'Addezio and Valensise, 1991), to blind strike slip
Eastern Sicily. Mem. Soc. Geol. Ital. 55, 61–70.
faulting parallel of the N–S Scicli line (Sirovich and Ben Avraham, Z., Boccaletti, M., Cello, G., Grasso, M., Lentini, F.,
Pettenati, 1999), to faulting along the NNW–SSE Malta Torelli, L., Tortorici, L., 1990. Principali domini strutturali