Abstract
We analyzed the instrumental seismicity of Southern Italy in the area
including the Lucanian Apennines and Bradano foredeep, making use
of the most recent seismological data base available so far. P- and
S-wave arrival times, recorded by the Italian National Seismic Network
(RSNC) operated by the Istituto Nazionale di Geofisica e Vulcanologia
(INGV), were re-picked along with those of the SAPTEX temporary array
deployed in the region in the period 2001-2004. For some events located
in the upper Val d'Agri, we also used data from the Eni-Agip oil
company seismic network. We examined the seismicity occurred during
the period between 2001 and 2006, considering 514 events with magnitudes
M>=2.0. We computed the VP/VS ratio obtaining a value of 1.83 and
we carried out an analysis for the one-dimensional (1D) velocity
model that approximates the seismic structure of the study area.
Earthquakes were relocated and, for well- recorded events, we also
computed 108 fault plane solutions. Finally, using 58 solutions,
the most constrained, we computed regional stress field in the study
area.Earthquake distribution shows three main seismic regions: the
westernmost (Lucanian Apennines) characterized by high background
seismicity, mostly with shallow hypocenters, the easternmost below
the Bradano foredeep and the Murge with deeper and more scattered
seismicity, and finally the more isolated and sparse seismicity localized
in the Sila Range and in the offshore area along the northeastern
Calabrian coast. Focal mechanisms computed in this work are in large
part normal and strike-slip solutions and their tensional axes (T-axes)
have a generalized NE-SW orientation. The denser station coverage
allowed us to improve hypocenters determination compared to those
obtained by using only RSNC data, for a better characterization of
the crustal and subcrustal seismicity in the study area.
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