769 ANNALS OF GEOPHYSICS, VOL. 51, N. 5/6, October/December 2008 Key words Southern calabria – Seismicity – Stress tensor – Attenuation – Source parameters 1. Introduction The Calabrian arc (fig. 1) is the most arcu- ate southern part of the Mediterranean orogenic belt. The arc connects the E-W and the NW-SE trending branches of the belt, which are repre- sented by the Maghrebian and the southern Apennines chains, respectively. The most im- pressive tectonic feature of the arc is a promi- nent normal fault belt that extends, more or less continuously, for a total length of about 180 km along the inner side of the arc (Tortorici et al., 1995). The morphological features of the fault escarpments suggest slip rates of 0.8-1.1 mm/yr for the last 700 k.y. and values of 0.6-0.9 mm/ yr for the last 120 k.y., indicating a uniform rate of faulting since the Middle Pleistocene (Tor- torici et al., 1995). The different normal fault segments separate the main Pliocene-Pleis- tocene basins from the uplifted mountain rang- es (Tortorici et al., 1995). The study area (fig. 1) is a ca. 40 km long section of the Calabrian arc that includes the Gioia-Tauro basin and the Aspromonte mountain range. In particular, the Gioia Tauro basin (fig. 1) is part of a system of basins that border the Serre-Aspromonte to- ward the western coast of southern Italy. It is characterized by the Cittanova fault (hereafter referred as CF), a well exposed west dipping high-angle normal fault about 20 km long, which separates metamorphic and igneous rocks to the east from sedimentary marine and continental successions to the west (Galli and Bosi, 2002). In the field, the CF appears both as a single ~10 m high scarp or as smaller multiple Seismological investigations in the Gioia Tauro Basin (southern Calabria, Italy) Elisabetta Giampiccolo ( 1 ), Carla Musumeci ( 1 ), Filippo Falà ( 2 ) and Stefano Gresta ( 2 ) ( 1 ) Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Catania, Italy ( 2 ) Dipartimento di Scienze Geologiche, Università degli Studi di Catania, Italy Abstract This study provides new seismological information to characterize the seismically active area of the Gioia Tauro basin (southern Calabria, Italy). Seismic activity recorded by a temporary network from 1985 to 1994 was analyzed for focal mechanisms, stress tensor inversion, P-wave seismic attenuation and earthquake source pa- rameters estimation. Fault plane solutions of selected events showed a variety of different mechanisms, even if a prevalence of normal dip-slip solutions with prevalent rupture orientations occurring along ca. NE-SW direc- tions was observed. Stress tensor inversion analysis disclosed a region governed mainly by a NW-SE exten- sional stress regime with a nearly vertical σ1. These results are consistent with the structure movements affecting the studied area and with geodetic data. Furthermore, evaluation of P-waves seismic attenuation and earthquake source parameters of a subset of events highlighted a strong heterogeneity of the crust and the presence of fault segments and/or weakened zones where great stress accumulation or long-rupture propagation are hindered. Mailing address: Dr. Elisabetta Giampiccolo, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy; e-mail: giampicco- lo@ct.ingv.it