[S-GC37] Volatiles in the Earth - from Surface to Deep Mantle

[SGC37-04] Monitoring dissolved gases in thermal water to assess the potential relation between fluid geochemistry and seismicity

★Invited Papers

*Sebastien Giroud^1,2, Yama Tomonaga^1,4, Matthias Brennwald¹, Rolf Kipfer^1,2,3 (1.Dept. of Water Resources and Drinking Water, Eawag, 2.Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 3.Institute of Geochemistry and Petrology, ETH Zurich, 4.Dept. of Environmental Sciences, University of Basel)

Keywords:seismicity, noble gases, geochemical changes

The relationship between dissolved gas concentrations in geological fluids and seismic activity is a topic of ongoing debate. While there have been several examples of correlations between changes in gas composition and seismicity, these are often based on observations of single events. Moreover, data from long-term systematic gas monitoring are hardly available. This leads to the difficulty and complexity of determining the causality between earthquakes and evolution of gas dynamics [1].

To address this issue, we deployed a portable gas equilibrium membrane-inlet mass spectrometer (miniRUEDI, [2]) at the hot springs of Lavey-les-Bains located in a seismically active region of Switzerland (range of geothermal fluids: 50 °C – 65 °C). This instrument provided high-frequency and long-term time-series of dissolved gas concentrations (e.g., He, Ar, Kr, N₂, O₂, H₂, CH₄ and CO₂), including data from over a year-long period. These data set the experimental basis to critically assess if gas evolution in geological fluids and seismicity are causally linked.

[1] Toutain et Baubron (1999), Tectonophysics, 304, 1-27
[2] Brennwald et al. (2016), ES&T, 50, 13455-13463