GNGTS 2015 - Atti del 34° Convegno Nazionale

GNGTS 2015 S essione 1.2 111 CNR (Carrozzo et al. , 1986; reduction density: 2.4 g/cm 3 ) were sampled with a step grid of 1 km. By including higher vertical derivatives, a better detail for shallower sources is obtained. For this study we computed MDA at three resolution scales to investigate structures of different depths and extents. However, in this paper the map obtained by computing a medium scale EHD, which yields insights about both shallow and deep structures has been used. A layer of gravimetric lineaments has been created with an associated attribute table in which they were entered, for each maximum MDA value, the correlation with the local topography, the probable fault and earthquakes associated. The merge of the three different datasets (faults, earthquakes and gravimetric lineaments) in GIS environment is shown in Fig 3. GIS allows us to work with different types of data in a one geographic reference system with the elaboration of thematic information and the creation of 2D and 3D representations of geodynamic phenomena. The analysis of the map (Fig. 3) shows a good correlation among earthquakes, faults and MDA lineaments along NW-SE and NNW-SSW alignments. These faults may be considered active. Among the most important tectonic structures recognized in this paper, we have concentrated our investigation on the Fucino and l’Aquila basins. The L’Aquila basin is marked by MDA maxima with NW-SE and NE-SW strikes. The Fucino basin seem to be surrounded by a series of MDAmaxima in the same directions (NW-SE and NE-SW), but more evident. However, the MDA maxima could also be generated by the strong contribution of the topography and so the effect of the faults could be hidden. Thus, it is important to understand if the maxima are created by the topography or by a fault. For example, if we have a strong maximum, but there is no correlation with the topography (such as a relief) the maximum could be generated by a buried or outcropping fault. For this reason we have used the MDA medium scale map, where the topography effect is less evident. In conclusion this study has highlighted four possible scenarios: 1) the existence of active faults, shown by a strong correlation among the epicentral location of seismic clusters matching the fault and MDA lineaments. 2) the existence of buried active faults, highlighted by a correlation of MDAmaximum with an associated spatial distribution of epicentral location, but without correspondence with faults known from geological data; 3) the existence of inactive or silent faults, detected by the presence of faults reported in the geological datasets and literature which are correlated with a MDA maximum, but without correlation of spatial distribution of earthquakes; Fig. 3 – Map of three different thematic layers: faults, earthquakes and medium scale MDA overlapped on shaded relief of topography.