Page 1 - Visini_de Nardis_Lavecchia_2010

Int J Earth Sci (Geol Rundsch) (2010) 99 (Suppl 1):S243–S264
DOI 10.1007/s00531-009-0473-x
ORIGINAL PAPER

Rates of active compressional deformation in central Italy
and Sicily: evaluation of the seismic budget

Francesco Visini Æ Rita de Nardis Æ Giusy Lavecchia

Received: 11 August 2008 / Accepted: 12 July 2009 / Published online: 5 August 2009
Ó Springer-Verlag 2009

Abstract Historical and recent seismicity records and shear zones, in agreement with recent horizontal GPS
available source mechanisms in eastern-central Italy motion model and other independent evidence.
(Marche–Adriatic region), in mainland-southern Sicily and
in the Tyrrhenian offshore of northern Sicily show com- Keywords Seismotectonics Active thrust faulting
parable deformation patterns. Seismotectonic consider- Seismogenic crustal deformation Sicily
ations indicate that each of the three areas represents a Marche–Adriatic region Southern Tyrrhenian Sea
broad seismogenic province of relatively homogeneous Italy
deformation. On the basis of the historical earthquake
catalogue, the parameters of the Gutenberg–Richter dis-
tribution have been calculated by means of a Monte Carlo Introduction
simulation method. The average moment tensors have been
computed from focal mechanism data and the strain rate Knowledge of the velocity and strain tensors of seismo-
and velocity tensors evaluated by means of Kostrov’s (in genic deformation is an essential tool for determining the
Izv Acad Sci USSR Phys Solid Earth 1:23–44, 1974) seismic hazard of an active region. Geological, geodetic
relation, which also considers the shape and size of the and seismological data may provide insights into the strain
seismogenic volume. The uncertainties have been system- fields, and their integration is necessary in order to obtain
atically incorporated. The results show that the three seis- more constrained and stable strain parameters and to
motectonic provinces are all undergoing shortening at improve estimates of earthquake forecast.
seismic rates (*0.3 mm/year in the WSW–ENE direction Geological data are capable of recording the long-term
in the eastern Marche–Adriatic region, *0.1 mm/year in deformation history of a region and the related strain
the N–S direction in mainland-southern Sicily and release patterns. Consequently, they may allow us to
*0.2 mm/year in the NW–SE direction in the Southern extend the history of slip of a seismogenic region to a large
Tyrrhenian zone). The motion pattern in the Marche– number of earthquake cycles (Yeats and Prentice 1996;
Adriatic and in the Sicilian provinces suggests that these Ward 1998; Papanikolaou et al. 2005). Obviously, the
areas undergo active crust-scale deformation along reverse completeness of geological strain rate depends on the
availability of quantitative geological data for the study
area. Well-constrained data such as the 3D geometry and
kinematics of the seismogenic structures, timing of the
F. Visini (&) G. Lavecchia deformation, accurate displacement evaluation and slip
Laboratorio di Geodinamica e Sismogenesi, Dipartimento di
Scienze della Terra, Universita ` ‘‘G. d’Annunzio’’, rates are not always available (Ward 1998; Roberts 2006;
Campus Universitario, 66013 Chieti Scalo, Italy Wallace et al. 2007).
e-mail: f.visini@unich.it Geodetic strain takes into account the total value of the
active deformation, but it is unable to discriminate the
R. de Nardis
Dipartimento della Protezione Civile, seismic components from the aseismic ones. Moreover, it
Servizio Sismico Nazionale, DPC-SSN, Rome, Italy is still unclear whether geodetic data can be extrapolated to

123