Publication Date:
2017-04-04
Description:
In this paper we present the first geochemical data set regarding long-term monitoring of dissolved gases in thermal waters from a seismic area. Three sites in Umbria (Central Apennines, Italy) were studied both for the chemical and for the helium isotopic composition of the dissolved gases. Data were collected during and after the seismic crisis that struck the region in 1997â 1998. The chemical composition of the dissolved gases revealed that a CO2-rich gas phase was always mixed with an atmospheric-derived component dominated by N2. A normal faulting marked the beginning of the seismic activity enhancing the release of CO2 on a regional scale. Variations in both the chemical and isotopic compositions of the dissolved gases were also observed as preseismic, synseismic, and
postseismic phenomena related to the seismic shock of March 1998. Those geochemical modifications were interpreted as being the consequence of a drop in the CO2 degassing rate, in good agreement with the compressive focal mechanism of that seismic event. Furthermore, this interpretation was also consistent with the geologic and tectonic setting of the study area and induced us to postulate that changes in the local rock permeability, due to crustal deformations (i.e., coseismic deformation and
postseismic release), were responsible for the geochemical modifications observed. On the basis of the foregoing, we have concluded that the geochemistry of dissolved gases in groundwaters
represents a useful tool for the investigation of the relationships between circulating fluids and seismic activity.
Description:
Published
Description:
partially_open
Keywords:
dissolved gases
;
geochemistry
;
seismic areas
;
04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes
;
04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
;
05. General::05.02. Data dissemination::05.02.01. Geochemical data
;
05. General::05.02. Data dissemination::05.02.04. Hydrogeological data
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Format:
337669 bytes
Format:
503 bytes
Format:
application/pdf
Format:
text/html
