Significance of earthquake-related anomalies in fluids of Val D'Agri (southern Italy)

Abstract

Geochemical investigations carried out at the Campano-Lucano Apennine (Southern Italy) revealed the presence of fluids composed of a mixing between components of shallow and deep origin, where mantle-derived helium is also detectable. For the gas phase, the deep component is represented by both CH4 and CO2-rich gases, while the shallow one is N2-dominated. Coinciding with the 3 April 1996 ML = 4.9 earthquake, the CH4- rich component mixed with the shallow, NZ-dominated one at the Tramutola well (Val dfAgri), displaying wide variations in mixing proportions. In contrast, no significant modificationsoccurred in relation to the 1998 ML = 5.5 event. According to the collected data, an earthquake-related transient modification of local crustal permeability is suggested for the 1996 event. The different crustal response to the two events may be related to different stress distributions around the epicentres or may suggest a different tectonic connection between the Val d'Agri and the two earthquake locations.