GNGTS 2014 - Atti del 33° Convegno Nazionale

model of Ponziani et al. , (1995) (Tab. 1). The density values obtained were compared with the density for the same crust used by many authors for gravity modelling at regional and local scale (Tab. 2). We used these values for estimating the reliability of calculated densities. Gravity Section. In this work in order to compare the suitability of the crustal models we made a first attempt studying the intermediate 2D section that extends for 170 km from the southern slope of M.Amiata to the Adriatic coast. It contains 144 gravity stations and shows the gravity signal of the main tectonic structures of the studied area (Fig. 1). Moving from the eastern part of the profile to Perugia regional gravity anomaly is positive with a maximum value of +40 mGal in correspondence of Perugia Massive, and negative with a minimum value of - 44 mGal in the Adriatic coast (Fig. 2). In the east side of the section, four relative gravity minimum are present: one located to the southern slope of M. Amiata (with a wavelength of about 20 km), and other in correspondence with the Radicofani Basin and Val di Chiana Basin (with a wavelength of about 10 km), and Tiber basin (with a wavelength of about 5 km). Our 2D section is close to M. Amiata and we had to consider the presence of an intrusive body. According to the following studies (Barberi et al. , 1994; Orlando et al. , 1994; Acocella, 2000) we defined in our model an intrusive body at a depth of about 5 km with a lenght of 15 km and a density of 2.4 g/cm 3 . In the section, we fixed the geometries of the sedimentary cover and we performed many gravity models changing the depth of lower crust and upper mantle following the information given by Ponziani et al. (1995), Piana Agostinetti et al. (2002) and Mele and Sandvol (2003). Summary and conclusion. The model presented is a preliminary result of a research project aimed to propose new gravimetric modelling of both deep and surface structures of northern Apennines (Fig. 3). The model shows how the two different crustal domains are recognizable in the gravimetric signals. The feature of the regional gravity response of this model and particularly the wide deficit mass observed beneath the western part of the section are caused by the doubling of Moho and the crustal root beneath the Apennine Chain. GNGTS 2014 S essione 3.2 155 Fig. 3 – Preliminary gravimetric model of the intermediate section, see text for details.