GNGTS 2013 - Atti del 32° Convegno Nazionale

Wessel P. and Smith W.H.F.; 1998: New, improved version of the Generic Mapping Tools released . Eos Trans. AGU, 79, 579. Williams, S.D.P., Bock, Y., Fang, P., Jamason, P., Nikolaidis, R-M., Prawirodirdjo, L., Miller, M., Johnson J., 2004. Error analysis of continuous GPS position time series, J. Geophys. Res. 109, B03412, doi:10.1029/2003JB002741. Williams, S.D.P., 2008. CATS: GPS coordinate time series analysis software, GPS Solutions 12(2), 147-153, doi:10.1007/ s10291-007-0086-4. 2D-3D GPR across theMt. Pollinoand Castrovillari faults (Southern Calabria): driving paleo-seismology researches in a complex site to infer Quaternary earthquakes M. Ercoli 1 , C. Pauselli 1 , E. Forte 2 1 Dipartimento di Scienze della Terra, Università di Perugia, Italy 2 Dept. of Mathematics and Geosciences, Università di Trieste, Italy Introduction. The definition of the seismic hazard of major seismogenic fault zones is often reached with the support of geophysical investigations to the geological and paleoseismological studies. Over the last years, paleoseismology investigates the subsurface through trenches realized across the fault branches (Galli et al. , 2008) and employing geophysical techniques like 2D-3D Ground Penetrating Radar (GPR) (Liner and Liner, 1997; Mc Clymont et al. , 2008; Pauselli et al. , 2010, Ercoli et al. , 2013). A multidisciplinary approach is particularly recommended on areas classified seismically “ silent ” from relatively long time and representing “seismic gaps”. On the other hand, these structures have morphological, geological and structural evidences compatible with the occurrence of past strong earthquakes, therefore any faults inside these “gaps” can be particular interesting for geoscientists in order to assess the seismic hazard. The knowledge of the characteristics and of the seismic behavior of the single fault segments, is fundamental to infer their evolution in the Quaternary age, to delineate which portion shows the highest probability of generate strong events, and to plan mitigation efforts for the area. The Mt. Pollino region can be classified as one of the most apparent “seismic gaps” along the central and southern Apennines seismogenic fault zone (Cinti et al. , 1997; Michetti et al. , 1997; Valensise and Pantosti, 2001), due to the historical seismicity and the poor “recent” instrumental activity consisting in small/moderate magnitude earthquakes (Ferreli et al. , 1994). Anyway, a recent paroxystic seismic activity, characterized by about 3400 seismic events of M>1, including an earthquake of M = 5.0 (2012/10/26, Mormanno) have been recorded during the last two years on the area surrounding Castrovillari, (ISIDe Working Group, INGV, 2010). The Project S1 “Miglioramento delle conoscenze per la definizione del potenziale sismogenetico” (Agreement INGV-DPC 2012-2013, https://sites.google.com/site/ progettisismologici/progetto-s1) is a recent integrated project started with two main aims: 1) to improve the base-knowledge for assessing the seismogenic potential of some areas considered of significant interest by the Project Board. 2) to develop innovative methodologies for the study of active faults, with a quantitative approach. The Pollino area, due to these uncertainties in the definition of the seismic hazard, is one of the zones studied during the last year. Among a broad spectrum of research topics and units, the project includes the GPR fault imaging on several sites close to Castrovillari, having different purposes: 1) to define the location and the geologic characteristics of the Quaternary faults in well-know sites; 2) to detect evidences of a geophysical signature interpretable with recent faulting extending the GPR surveys to new study sites; 3) to map these geological structures on thematic maps; 4) to support and drive new paleoseismological surveys. We collected 2D-3D GPR data on the Mt. Pollino and the Castrovillari Faults (Fig. 1) in several sites. A first 2D-GPR survey was done at the “Grotta Carbone” site in order to calibrate the data with available trench logs (Michetti et al. , 1997). The surveys have been extended to 169 GNGTS 2013 S essione 1.2