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Soil gas distribution in the main coseismic surface rupture zone of the 1980, Ms = 6.9, Irpinia earthquake (southern Italy)

 

Ciotoli, G. 2, S. Bigi2, C. Tartarello2, P. Sacco2, S. Lombardi2, A. Ascione1, and S. Mazzoli1

 

1 Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università degli Studi di Napoli Federico II, Largo San Marcellino 10, 80138 Napoli, Italy

2 Università di Roma La Sapienza

 

J. Geophys. Res. Solid Earth, 119, 2440–2461, 2014

doi:10.1002/2013JB010508

 

 Abstract

jgrb50469-fig-0003Soil gas measurements of different gas species with different geochemical behaviors were performed in the area of the Pecore Plain, a 200m Å~ 300m sized, fault-bounded extensional basin located in the northern Mount Marzano massif, in the axial belt of the southern Apennine chain. The Pecore Plain area was affected by coseismic surface faulting during the Ms = 6.9, 1980 Irpinia earthquake, the strongest and most destructive seismic event of the last 30 years in southern Italy. The collected data and their geostatistical analysis provide new insights into the control exerted by active fault segments on deep-seated gas migration toward the surface. The results define anomalies that are aligned with the NW-SE trending coseismic rupture of the 1980 earthquake along the western border of the plain, as well as along the southern border of the plain where a hidden, E-W striking fault is inferred. Geospatial analysis highlights an anisotropic spatial behavior of 222Rn along the main NW-SE trend and of CO2 along the E-W trend. This feature suggests a correlation between theshape and orientation of the anomalies and the barrier/conduit behavior of fault zones in the area. Furthermore, our results show that gas migration through brittle deformation zones occurs by advective processes, as suggested by the relatively high migration rate needed to obtain anomalies of short-lived 222Rn in the soil pores.

 

Key-words: active tectonics, normal faults, Apennines