The application of a stacking method to detect weak tidal modulation of thermometric signals recorded at Mt. Etna

Volcanic areas are characterised by high heat fluxes due to the presence of magma bodies near the surface. In these areas the convection is the major heat transfer mechanism. The strain field within the volcanic edifice due to the gravitational forces exerted mainly by the Sun and the Moon (tidal stress) could affect this convective process. Time variations of the efficiency of the convective process should produce corresponding temperature changes observable at shallow depth. In the present work, we analysed a thermometric signal recorded on Etna volcano at a site very close to the main active craters. The aim of the study was to investigate about the presence of periodic variation due to the main lunar tidal component (M2). This component was chosen in order to avoid the solar radiation effects. The data set at hand was processed with a stacking technique coupled with a wavelet analysis for a preliminary denoising. Through this procedure an anomalous amplitude of the spectral component with a period equal to that of M2 tidal wave was found in the studied thermometric record. The coincidence among M2 tidal period and that of the observed temperature signal could suggest a physical interaction between the two phenomena.