Gravity tide in the neapolitan volcanic area

Recording gravity stations are operating in volcanic areas aimed at the geophysical monitoring of the volcanic activity. The availability of reliable models of the gravity tide in a volcanic area is the main condition to extract from the gravity records the signal possibly associated to volcanic sources.Gravity records, spanning about 4 years, collected in different time intervals, respectively during 90's at Vesuvio and recently at Napoli stations have been analyzed. The sites where spring gravimeters (LCR, G and D) are recording are also sites surveyed by absolute and relative gravity measurements carried out to monitor the volcanic activity.The records have provided models of the gravity tide for both the areas; the knowledge of the gravity tide is also useful to a precise reduction of discrete absolute and relative measurements. Moreover the residual tidal vectors have been computed in order to take into account the contribution of the ocean tide loading to the body tide. The WDD Earth Model has been adopted as a reference in the computation of the residual vectors for the main tidal waves. The components of such residuals provide information about the sensitivity and reliability of the scale factors adopted to calibrate the gravimeters.