Seismological temporal patterns at Mefite d’Ansanto CO2 emission field.

Vienna, Austria

Mefite d’Ansanto (Italy) is the largest non-volcanic CO2 emission field on the Earth. The isotopic
signature of the CO2 testifies a deep origin of the gases emitted at this site, whose source is
probably the mantle wedge beneath the Apennines along the Tyrrhenian side (Chiodini et al.,
2010). Mefite is located between the Sannio and the Irpinia seismogenic regions, that are
considered among the most active areas of the southern Apennines. The emission site falls at the
northern tip of the Irpinia fault system that is associated with the destructive MS = 6.9, 1980 Irpinia
earthquake. The gas leakage from this zone is linked to active faulting that characterized the area
and determined large historical earthquakes
A temporary acquisition survey close to the Mefite emission field was carried out between 8 June
and 28 September 2020 by using a seismic array, named Array MEfite (AME), composed of seven
short-period stations. We have analyzed the characteristics of the recorded background seismic
noise, e.g., spectral properties, energy temporal pattern (RMS) and polarization (Montalbetti et al.,
1970), and estimated site effects (Nakamura, 1989; http://www.geopsy.org/). The seismological
temporal patterns have been compared with the meteorological parameters, such as temperature
and rainfall, to find possible relationships with exogenous factors. We found a well-defined spatial
pattern for the spectral components above 5 Hz, which appear clearly linked to the emission field
dynamics. On the other hand, the spectral components below 5 Hz result from the overlapping of
multiple sources, of both exogenous, such as anthropogenic and meteorological factors, and
endogenous nature. Application of the Independent Component Analysis (ICA) technique
(Hyvärinen et al., 2001) contributed to discriminate between natural and anthropogenic sources.

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Hyvärinen, A., Karhunen, J. & Oja, E. (2001). Independent Component Analysis. Wiley, New York,
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Nakamura, Y. (1989). A method for dynamic characteristics estimation of subsurface using
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