A strategy to study the effect of rainfall and snow melting on gravity recordings from a superconducting gravimeter installed on Mt. Etna volcano, Italy

We study the transient effect of groundwater mass changes on the observed gravity signal from a superconducting gravimeter deployed on Mt. Etna, Italy. Gravimeters are capable of detecting minor changes in the vertical component of gravity over time scales from minutes to years. Insight on geophysical phenomena that cause mass displacements in the subsurface can be obtained through the use of gravimetry. Gravity recordings integrate multiple components that contribute to the signal with different magnitudes. The effects of earth tides, atmospheric pressure changes, hydrological processes are among the above components. They need to be precisely evaluated, in order to isolate the signal caused by the volcanic processes. Here, we study the effect of groundwater mass changes on gravity, as a result of rainfall and snow melting, the latter estimated through GNSS interferometric reflectometry. A forward charge-discharge model is used to compare gravity recordings between 2018 - 2019 with observed precipitation events. We show that the observed gravity signal cannot be explained only through changes in groundwater mass, implying that other (volcanic) processes must have been at play.