GNGTS 2018 - 37° Convegno Nazionale

186 GNGTS 2018 S essione 1.2 GEOGENIC RADON AS GEOPHYSICAL TRACER OF ACTIVE FAULTS: THE FUCINO PLAIN (CENTRAL ITALY) G. Ciotoli 1,2 , L. Ruggiero 3 , G.P. Cavinato 1 , L. Modesti 2 , S. Bigi 2 , V. Romano 4 1 Institute of Environmental Geology and Geoengineering, National Research Council, Rome, Italy 2 National Institute of Geophysics and Volcanology, Rome, Italy 3 Department of Earth Sciences, Rome University Sapienza, Rome, Italy 4 Dept. of Geology, University of Illinois, Urbana-Champaign, USA Introduction. In geosciences, the analysis of the spatial distribution of radon ( 222 Rn) concentrations in the shallow environment provides insights into a range of primary spatial/ temporal geochemical/geophysical processes. Among the soil gases, 222 Rn is considered a convenient fault tracer, because of its ability to migrate to long distances from host rocks, as well as the efficiency of detecting it at very low levels. In the scientific literature, many papers are focused on Rn as tracer of hidden faults, and reported Rn anomalies significantly higher than background levels along active faults and associated fracture zones (King et al. , 1996; Ciotoli et al. , 2007, 2014, 2016; Davidson et al. , 2016). Evidences suggest that these anomalies can provide reliable information about the location and the geometry of active faults, and the width of the surrounding fracture zones (also if buried under the sedimentary cover) (Ciotoli et al. , 2016, 2007; Seminsky et al. , 2014). In this work, new soil gas measurements were carried out at different scales across known and inferred structural discontinuities in the Fucino plain (central Italy) in order to homogenise and densify the sampling reported in Ciotoli et al. , 2007. Dataset has been re-interpreted by using new GIS and geospatial analysis techniques and discussed in the light of new seismic data interpretation (Cara et al. , 2011). In particular, the correlation between the distribution of radon anomalies and the offsets measured along the San Benedetto-Gioia dei Marsi Fault (SBGMF) are discussed. Furthermore, new hypotheses are proposed regarding the link between radon migration and the process of fault evolution during the progressive linkage mechanism of several fault segments. Fig. 1. Main known and buried and faults of the Fucino plain. ACF, Avezzano-Celano fault; SSMF, Statale Marsicana fault; SBGMS, San Benedetto- Gioia dei Marsi fault; OF, Ortucchio fault, TF, Trasacco fault; LMF, Luco dei Marsi fault. The thickness of the line indicates the fault offset as reported in Cara et al. , 2011. Map limits are in WGS84 decimal coordinates.