GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 1.1 71 distributed in two clusters: a larger one to the W below Mormanno (MMN station) where the M L =5.0 event occurred, and a smaller one to the E, closer to Castrovillari town, where the M L =4.3 event occurred. In the map of Fig. 3 these two larger events are represented by the purple stars and earthquakes with magnitude larger than 3.5 are the yellow stars. The swarm like activity, of November 2011-May 2012 and again August 2012-November 2012, seems to be concentrated mainly in the northwestern part of the activated fault system and occurred on a diffuse crustal volume more than on fault planes (see sections in Fig. 3). The western cluster is active since the end of 2011: in its northern portion (section 3) hypocenters are localized in a ball-shaped volume, while in the southern part (section 5) hypocenters define a SW-dipping fault plane. The plane was imaged by the seismicity also in the period before the M L =5.0 event. In the section 5 it is also visible an antithetic fault plane to the W. Even if the eastern cluster has a lower number of refined locations, nevertheless the hypocenters define a NE-dipping plane, which seems related to the occurrence of the M L =4.3 event of May 2012. Conclusion. ��� �������� �������� �� ��� ���������� ��� ����� �� ���� � ������ ��� The geometry depicted by the seismicity and shown in Fig. 3 images the activated fault system: i) it affects the shallower 10 km of the crust; ii) it is constituted by at least three faults shorter than 10 km; iii) it strikes about NW-SE. The dip of the fault of the M L =5.0 event is toward SWwhile the two other smaller faults dip toward NE. A similar geometry of the main fault has been pointed out Totaro et al. (2013), although with lower resolution Comparing our results with the seismogenic sources reported in the DISS we find that the activated fault system is placed between the two major faults reported in this Database. The geometry of the “Rimendiello-Mormanno” fault system, constrained by geological data, is roughly consistent with the trend of the recent seismicity, but its dip is to the NE. The “Pollino” source (Castrovillari Fault, according to Cinti et al. , 1997) has a comparable trend (N20W) and a western dip, as the 2010-2012 seismicity, but its northern edge corresponds with the southernmost epicenters. Lastly, the fault systems described by Brozzetti et al. (2013), in the detailed structural map, shows several faults that could be connected to the faults depicted by the seismicity at depth. The scientific developments of this work will aim at a better understanding of the origin of the ongoing seismic activity in the Pollino area. Furthermore we are analyzing thousand of seismograms looking for anisotropic parameters, by means of Anisomat code (Piccinini et al. , 2013); and tomographic vp and vp/vs models, by means of Simulps14q code (Haslinger, 1998) to gain a better understanding of the ongoing seismic activity and to yield a better correlation between the fault structures at the surface and at depth. References Amato, A. and F. Mele (2008). Performance of the INGV National Seismic Network from 1997 to 2007, Annals Geophys., 51, n. 2-3, 417-431. Amato, A., Cecere G., Chiarabba C., De Gori P., Di Bona M., Gervasi A., Govoni A., Lucente F.P., Margheriti L., Mele F., Moretti M., Scognamiglio L., Selvaggi G., and E. Tinti (2012). Seismic activity in the Pollino region (Basilicata- Calabria Border). Atti del 32° Convegno GNGTS, Potenza, Italy. Brozzetti, F., LavecchiaG., ManciniG., MilanaG., and M. Cardinali (2009). Analysis of the 9 September 1998 Mw 5.6 Mercure earthquake sequence (Southern Apennines, Italy): A multidisciplinary approach. ��������������� ���� Tectonophysics, 476, 210–225. Brozzetti, F. (2013). Structural map of active faults in the Calabro-Lucania region, INGV-DPC, S1 project 2012-2013, Final Report, 364-385. Chiarabba, C., Jovane L., and R. Di Stefano (2005). � ��� ���� �� ������� ���������� ����� �� ����� �� ������������ A new view of Italian seismicity using 20 years of instrumental recordings. Tectonophysics, 395, 251–268. doi:10.1016/j.tecto.2004.09.013. Cinti, F.R., Cucci L., Pantosti D., D’addezio G., and M. Meghraoui (1997). A major seismogenic fault in a “silent area”: the.Castrovillari fault (southern Apennines, Italy). Geophys. J. Int., 130, 595-605. D’Agostino, N., and G. Selvaggi (2004). Crustal motion along the Eurasia-Nubia plate boundary in the Calabrian Arc and Sicily and active extension in the Messina Straits from GPS measurements. J. Geophys. Res., 109, B11402,. doi:10.1029/2004JB002998. D’Agostino, N. (2013). GPS velocity and strain field in the Calabro-Lucania region. INGV-DPC, S1 project 2012- 2013, Final Report , 314-321.