GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.3 275 Fig. 2 - Variation of N 2 (green circles; left axis) and O 2 (red circles; right axis) concentrations measured by the CMS. Fig. 3 - Variation of H 2 concentration measured by the CMS (orange circles; left axis) and air P (black triangles; right axis). that could somehow justify these variations was recorded beneath the bay, or very close. Three events (ML from 1.6 to 2.7) were located at 134 to 266 km depth with epicenters 25 km afar or more. One ML= 1.7 event was only ten km deep and ~22 km afar, but no correlation can be observed between this event and anomalous behavior in gas variation. A statistical analysis of the gas concentration was performed (Fourier transform) which allowed to highlight a main cyclicity at 24 hours especially for H 2 and CH 4 . Less evident is the daily ciclicity of CO 2 and O 2 . N 2 and H 2 S show a 48 hours ciclity. Helium doesn’t show apparent ciclicity. Besides the main long-term variations, air pressure has a daily ciclicity, as it can be expected. Although these considerations on the cyclicity are linked to a too short time