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Int J Earth Sci (Geol Rundsch) (2010) 99 (Suppl 1):S243–S264 S245

southern Sicily in the NW–SE direction at *3 mm/year earthquake distribution data, also integrated with kinematic
(Ferranti et al. 2008) and across the southern Tyrrhenian data referring to the long-term (generally the last 6 Ma)
strip in the NW–SE direction at *2 to 4 mm/year (Jenny history of geological deformation.
et al. 2006; Serpelloni et al. 2007). Cristofolini et al. (1985) and Lavecchia et al. (1994)
The aim of our study is to provide an evaluation of the stressed the importance of such a 3D stress-field insight
seismic deformation budget over a period of nearly into the definition of the seismotectonic domains for Sicily
400 years for the active compressional domains of central and for Central Italy, respectively. They all interpreted the
Italy (Marche–Adriatic area) and of Sicily (offshore and present seismicity in the frame of a progressive long
onshore), where active shortening evaluation from geo- history of deformation characterised by the outward
logical data is difficult and continuous geodetic observation migration, with time, of the thrust belt foredeep system,
exists only for the last decade, with a non-optimal network synchronous to that of the coaxial extensional domain
configuration (RING, Selvaggi 2006; IGFN, Vespe et al. extension in the rear. This contraction–extension pair is
2000). Computed seismic strain rate and velocity tensors still active today, as witnessed by the coexistence of
will allow us to compare the three study areas in terms of seismogenic extension in the Apennines and northern
seismogenic activity and will give a term of comparison Sicily and of seismogenic compression along the Padani-
with the deformation budgets computed with different an–Adriatic and Sicilian outer thrust systems.
methodological approaches, highlighting the possible gap The seismotectonic zones proposed in the course of the
in seismic release with respect to the overall seismogenic years by various authors for central Italy have remained
potential. We will adopt a procedure which takes into substantially unchanged (Fig. 2a and references therein).
consideration both geological and seismological data input Four zones, elongated in an average NW–SE direction, are
(Papazachos and Kiratzi 1992). The earthquake data have delineated from west to east. They are the Tuscan–Latium
been derived from two datasets. The first one, used for the thinned crust province with a very low extensional seis-
computation of the moment magnitude relations, consists micity, the highly seismogenic intra-Apennine province
of a list of M w C4.5 historical events; the second one, used which is undergoing SW–NE extension, the moderately
to get the tensor components, consists of a compilation of seismogenic pede-Apennine province which is undergoing
the available fault plane solutions of major and minor SW–NE contraction at mid-deep crust level and the
earthquakes. Geometric parameters of the seismogenic Marche–Adriatic coastal province, which is undergoing
volumes involved in the deformation have been assumed upper crust contraction. The latter is characterised by
from previous papers (Lavecchia et al. 2007a, b), where active folds, thrusts and strike–slip faults nucleated since
they had been derived from an integrated analysis of geo- middle Pliocene times.
logical, geophysical and seismological data. More controversial is the situation for Sicily, where
substantially different zonations have been proposed year
by year. At the beginning (Barbano et al. 1979; Working
Seismotectonic framework Group GNDT 1982), the main traits of the Sicilian zonation
consisted of three seismotectonic zones running roughly
In the last 25 years, three well-known seismotectonic east–west and corresponding, from north to south, to the
zonings of the Italian territory have been elaborated in the northern Sicilian active extension domain, to the mainland
frame of three national multidisciplinary research projects: Sicilian active compressional domain, and to the active
Progetto Finalizzato Geodinamica developed in the early foredeep and foreland domains. Subsequently, (Fig. 2b1) in
1980s (Working Group GNDT 1982), Gruppo Nazionale northern Sicily the E–W extensional zone was substituted
per la Difesa dei Terremoti developed in the early 1990s by a WNW–ESE transpressional zone and mainland Sicily
(Scandone et al. 1992; Meletti et al. 2000; Scandone and was interpreted as a completely aseismic domain. In wes-
Stucchi 2000) and INGV-DPC-Redazione della Mappa tern Sicily, a N–S strike–slip zone (Michetti et al. 1995),
di Pericolosita ` Sismica developed in the early 2000s which would accommodate a differential foreland flexure
(Working group MPS 2004a; Meletti et al. 2008). The retreat, was identified and was considered responsible for
corresponding elaborated seismic source models are known the Belice event in 1968. In addition (Fig. 2b2), an E–W
in the Italian scientific community as ZS-PFG, ZS4 and zone undergoing N–S compression was identified off the
ZS9, where ZS stands for Zonazione Sismotettonica. The northern coast of Sicily (Working group MPS 2004b).
common methodological approach has been the kinematic More recently, (Fig. 2b4, b5), a large domain undergoing
one; this means that the boundaries of the seismic zones nearly N–S compression across mainland and southern
correspond to the surface projection of kinematically Sicily was identified by Jenny et al. (2006), based on
homogeneous, active, domains defined on the basis of a geodetic-seismological data, and by Lavecchia et al.
cross-correlation of structural–geological data and 3D (2007a), based on geological–seismological data.

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