Statistical approach for the geochemical signature of two active faults in the western Corinth Gulf rift (Greece)

Soil–gas measurements of different gas species were performed in two distinct areas of the Corinth Gulf
Rift (Greece): the Aigion-Neos Erineos-Lambiri (ANEL) fault zone and the Rion-Patras fault zone. Both
zones lie in one of the most seismically active areas of the Euro-Mediterranean region, where a fast-opening
continental rift is located. In particular, the geochemical investigations were focused on fault segments
and fracture systems previously inferred by geomorphological, lithological and structural studies.
In this work the applicability of soil–gas geochemistry surveys for the exploration of buried/hidden
faults was tested by using various statistical methods. Moreover, a comprehensive geostatistical treatment
of the collected data provided new insights into the control exerted by active structures on
deep-seated gas migration towards the surface. In both investigated areas, the highest 222Rn and CO2 concentration
peaks correspond with zones where the interaction among fracture and fault segments was
inferred by structural and morphological methods. This indicates a clear correlation between the shape
and orientation of the anomalies and the different attitude and kinematic behavior of the faults recognized
in the two areas. Furthermore, obtained results show that gases migrate preferentially through
zones of brittle deformation by advective processes, as suggested by the relatively high rate of migration
needed to obtain anomalies of short-lived 222Rn in the soil pores