GNGTS 2016 - Atti del 35° Convegno Nazionale

176 GNGTS 2016 S essione 1.1 Fig. 2 – 2013-2015 seismicity and fault map of the Mercure Basin (MB) and surroundings (SAB=Sant Arcangelo Basin). Faults: CPST=Castello Seluci-Piana Perretti-Serra Mancieri-Timpa della Manca; MSF=Madonna del Soccorso; CaF=Castelluccio; RF=Rotona fault; MF1, MF2=Mercure fault 1, 2, which are considered the seismogenic sources of the 2010-2013 sequence. Sources: Brozzetti et al. (2009); Totaro et al . (2015). Inverted triangles are INGV stations used in this study. were re-located (Fig. 2) and ~25 well-constrained focal mechanisms were computed. The epicentral distribution is nearly parallel to the mapped faults and to the axis of the chain (Fig. 2). The concentration of events SE of the Mercure basin falls in the same area affected by the Pollino seismic sequence. The hypocenters distribution show that about 85% of the events are confined between ~5-12 km depth, whereas the remaining events have depth between 16 and 22 km (Fig. 2). Fault plane solutions of the 5-12 km deep events show an extensional kinematics with prevailing NNW-SSE to NW-SE trending nodal planes. The trend of the T-axes ranges from ENE-WSW to NE-SW (Fig. 3) and keeps sub-orthogonal to the mapped normal faults (Fig. 2). The projection of nodal planes from the focal depth to the surface suggests possible relation with the mapped normal faults (Brozzetti et al. , 2009; Totaro et al. , 2015). Although the dataset is relatively limited, we found that some events are consistent with activation of the deep (5- 12 km) parts of the WNW-ESE striking Castelluccio and Castello Seluci-Piana Perretti faults (thick solid faults in Fig. 2). The latter fault, including its southward extension to Timpa della Manca (CPST fault), was considered the seismogenic structure of the Mw=5.5 1998 earthquake by Brozzetti et al. (2009).