GNGTS 2015 - Atti del 34° Convegno Nazionale

spherical plate, but that are below the top of planar Bouguer plate. The estimated density value for CB and CT corrections was 2.00 g/cm 3 , bearing in mind that the elevations range from -2.30 to 14.20 m asl and the shallow subsurface is composed of loose, fine sediments. The cumulative error of the gravity anomalies is equal to the square root of the estimated errors of the individual components involved in the calculations above briefly described; the estimated error is of the order of ±0.035 mGal. As well known, the observed Bouguer anomaly is the summation of the gravity effects related to deep anomalous bodies with shallower ones: the different effects can be recognized by the different curvatures, weaker for deeper bodies, steeper for shallow ones. A lot of strategies were introduced to separate the contributions of the deeper sources from the shallower ones. Among them, the upward continuation, the calculation of the horizontal and vertical gradients and the least-square residual anomaly separation were applied to the map reported in Fig. 2a. The upward continuation smooths the effects of the higher frequencies to enhance the lowers: an approach based on the equivalent source technique (Dampney, 1969; Xia et al. , 1993) was used to carry out this analysis. The heights of the upward continuation spanned from -1 to -5 km: the results show that the overall anomaly pattern that increases the height, is mainly due to the deepening of the basal detachment of the Apennines accretionary wedge. Fig. 2 – a) Bouguer anomaly over the transect and b) along the investigated profile. c) Residual anomaly over the transect and d) along the investigated profile. 130 GNGTS 2015 S essione 1.2