Results concerning the modeled and observed tidal factors at Mt. Etna and Stromboli volcanoes (Italy)

Tidal gravity observations performed in the last few years, both at Mt Etna and Stromboli, have revealed the necessity of improving the tidal analysis in order to get the best corrected data for the detection of volcano related signals. On Mt. Etna the sites are very close to each other and the expected tidal factors differences are negligible. It is thus useful to try to unify the tidal analysis results of the different data sets on a unique tidal model. In order to get the best model for the gravity data tide correction, we compared the results and finally we normalized all the estimated tidal factors with respect to the best data set. The change in time of the gravimeters sensitivity is also an important issue to be checked since it affects the quality of the data and thus the results of tidal analysis. Conversely, if a good tidal model is available, the sensitivity variations can be accurately reconstructed such as to retune observed tidal records with the synthetic tide, since the tidal parameters are assumed as constant. Subsequently, we tried to check if a tidal modulation exists on the heat flow beneath the gravity station, by using two temperature signals recorded inside and outside it. This analysis suggests an unexpected correlation between thermometric observations and some lunar tidal components.