Page 1 - LaVecchia_Ferrarini_alii_2007

Available online at www.sciencedirect.com

Tectonophysics 445 (2007) 145–167
www.elsevier.com/locate/tecto

Active thrusting as a possible seismogenic source in Sicily
(Southern Italy): Some insights from integrated structural–kinematic

and seismological data

a,⁎ b c
Giusy Lavecchia , Federica Ferrarini , Rita de Nardis ,
a
Francesco Visini , Maria Serafina Barbano d
a
Laboratorio di Geodinamica e Sismogenesi, Dipartimento di Scienze della Terra, Università “G. d'Annunzio”,
Campus Universitario, 66013 Chieti Scalo, Italy
b
Dipartimento S.T.A.T., Università degli Studi del Molise, Contrada Fonte Lappone, 86090 Pesche (Isernia), Italy
c
Dipartimento della Protezione Civile, Servizio Sismico Nazionale, DPC-SSN, Roma, Italy
d
Dipartimento di Scienze Geologiche, Università di Catania, Corso Italia 55, 95129 Catania, Italy
Received 13 September 2006; received in revised form 18 July 2007; accepted 21 July 2007
Available online 3 August 2007

Abstract

This paper proposes a new seismogenic interpretation of mainland and central-southern Sicily, based on an integrated
structural–kinematic–seismological approach. Through analysis of available structural and geophysical data, the tectonic setting,
the major kinematic units and the crust geometry of the Sicilian southward-verging fold-and-thrust belt system are schematized in
sections and in map form. The depth-contour lines of the outermost basal thrust plane, which dates back to Plio-Pleistocene times
with some evidence of Holocene activity, are reconstructed. This plane, here named Sicilian Basal Thrust (SBT), emerges along the
southward convex Sciacca–Gela–Catania front and reaches the base of the crust at a depth of about 30 km beneath northern Sicily.
Additionally, an important regional upper crust splay, with the same arched shape, has been identified some kilometres northward.
In order to detect any possible indication of seismogenic activity linked to ongoing deformation of the SBT and its splay, we
analyzed the distribution and kinematics of the instrumental seismicity in the period between 1981 and 2006. Particular attention
was given to the background seismicity (Ml up to 4.6) located beneath the sedimentary cover at Mt. Etna, as it allows individuating
a northward deepening seismogenic volume undergoing an average N–S compression, which corresponds well with the SBT
geometry in section view. A merged dataset of all the known major historical and instrumental events (moment magnitude ≥ 4.5)
that occurred above the SBT 0-to-30 km depth-contour lines from 217 B.C. to 2006 was compiled and analyzed. Based on
information from instrumental data and/or on speculations on the shape and extent of the historical earthquake macroseismic fields,
two major ranges of hypocentral depths have been schematically identified within the merged dataset: an upper crust range (in
average b~ 10 km) and a mid-to-lower crust range. Focal mechanisms available in the literature show prevailing reverse and
reverse-oblique kinematics, compatible with a nearly average N–S shortening and with some field evidence of active fold-and-
thrust deformation at the SBT front and along its inner splay. Several moderate earthquakes (nearly 40 in the last 400 years with
moment magnitude ranging from 4.5 to 5.5) and a few more energetic events with moment magnitude up to ~ 6.0, such as the
Mineo 1624, the Belice 1968 and the Catania 1818 events, can be attributed to an ongoing activity of the SBT. In previous studies,
these events had been often attributed to isolated N–S strike-slip sources located within the Hyblean-Pelagian foreland, while all
the interposed areas had been considered aseismic, as well as the SBT had been considered inactive. The identification in the SBT

⁎ Corresponding author. Tel.: +39 0871 3556415.
E-mail address: glavecchia@unich.it (G. Lavecchia).
0040-1951/$ - see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.tecto.2007.07.007