GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 1.1 145 areas. Gravity data are extracted from the Bouguer Gravity Anomaly Map of Italy published by CNR (Carrozzo et al. , 1986; reduction density: 2.4 g/cm 3 ) with a step grid of 1 km. The inclusion of higher vertical derivatives in the EHD allows a good detail for shallower sources. By computing a medium scale EHD, we are able to recognize both shallow and deep structures. From the MDA gravimetric maps, we have mapped the gravimetric lineaments and created a layer with an associated attribute table in which, for each MDA maximum, we reported the correlation with the local topography and the correlated fault and earthquakes. Moreover, we used the DEXP method ( Depth from Extreme Points , Fedi, 2007; Fedi and Pilkington, 2012) to constrain the geometry of the identified seismogenic faults (dip angle). The three different datasets (faults, earthquakes and gravimetric lineaments) were overlapped above the DEM of the studied areas. This multi-method approach allowed us to highlight four possible scenarios: • � ������ ����������� ������� ������ ���������� �� ����������� ����������� ���������� a strong correlation between faults identified by literature, earthquakes epicentral distribution and MDA lineaments could confirm the presence of active faults already known in literature; • � ����� ����������� ������� ��� ������ ��� �� ���������� ������� ������������ �� a clear correlation between MDA maxima and an associated spatial distribution of earthquakes epicentral location, but without the presence of faults known from geological data, could suggest the existence of buried active faults; • ��� �������� �� ��� ������ ���������� ���� ������ �������� �� ��� ���������� �������� the presence of MDA maxima correlated with faults reported in the geological datasets and literature but with no associated earthquakes could imply the existence of inactive or silent faults; • ��� ��������� �� ������� ���� ������ ��� ��������� ���������� ���� ��� ���������� ��� ��� the existence of faults, both active and inactive, identified from the literature but not correlated with MDA maxima could be due to faults putting in contact two lithologies with a similar density. In Fig. 1 we show the map of faults and earthquakes overlapped on medium scale MDA of the study areas. The Abruzzo region is marked by MDA maxima with NW–SE and NE–SW strikes. Our study is focused on the area hit by the 2009 L’Aquila seismic sequence. A trend of MDAmaxima runs parallel to the Paganica Fault but shifted westward of about 6 km. In the hypothesis of correlation with a tectonic contact, this trend is compatible with a fault model displacing rocks with different densities in the depth range of 5–15 km, along a flat surface dipping westward with an angle of 45°. A good agreement exists between such a model surface and the fault plane defined by the hypocenters of the seismic events correlated to the Paganica Fault (Chiaraluce et al. , 2011), even though they are limited within the depth range of 4–10 km (Luiso et al. , 2016a). This suggests that only the intermediate part of the fault plane could have been reactivated during the recent 2009 seismic swarms.  The San Giuliano di Puglia area, hit by the 2002–2003 seismic sequence, is marked by strong Apennine MDA anomalies and minor anti-Apennine ones. The town of San Giuliano di Puglia is located above a NW–SE normal fault dipping SW, characterized by scarce seismicity. The seismic swarm is concentrated in the western part of the area correlated with different trends of gravimetric anomaly, including an E–W MDA maximum (Luiso et al. , 2016b). The third studied area, the Mt. Massico area, is bordered by two NE–SW gravimetric anomalies, coincident with two normal faults known from the literature (Gaudiosi et al. , 2012). The 3D hypocentral map of earthquakes after relocation highlights clustering of events coincident with the two main faults. Conclusion. In this paper a multiparametric data analysis has been applied to the Abruzzo (central Italy), San Giuliano di Puglia (Molise, southern Italy) and Mt. Massico (Campania, southern Italy) areas through merging of seismicity, tectonic and gravity data, with the aim of identifying structural lineaments responsible for seismic activity. Accordingly, three thematic data sets have been generated for these areas: “fault”, “earthquake” and “gravimetric” datasets, in order to collect and integrate the whole set of existing information. The GIS system has