Earthquake-induced structural deformations enhance long-term solute fluxes from active volcanic systems

Takahiro Hosono (1, 2, 3) , Jens Hartmann (1, 4) , Pascale Louvat (5) , Thorben Amann (4) , Kirstin E Washington (6) , A Joshua West (6) , Koki Okamura (2) , Michael E Böttcher (7) , Jérôme Gaillardet (3)

1 Kumamoto University
2 Department of Earth and Environmental Science [Kumamoto]
3 IPGP - Institut de Physique du Globe de Paris
4 Institute for Geology, Universität Hamburg, Center for Earth System Research and Sustainability (CEN), Bundesstrasse 55, 20146, Hamburg, Germany
5 IPGP - Institut de Physique du Globe de Paris
6 Department of Earth Sciences [University of Southern California]
7 Geochemistry & Isotope Biogeochemistry Group, Leibniz Institute for Baltic Sea Research (IOW), Seestrasse 15, D-18119, Warnemünde, Germany

Evidence for relationships between seismotectonic activity and dissolved weathering fluxes remains limited. Motivated by the occurrence of new springs emerging after the 2016 Kumamoto earthquake and supported by historical groundwater data, this study focuses on the long-term effect of near-surface structural deformation on the contribution of deep, highly saline fluids to the solute fluxes from the Aso caldera, Kyushu, Japan. Available hydrologic and structural data suggest that concentrated, over-pressured groundwaters migrate to the surface when new hydraulic pathways open during seismic deformation. These new springs have a hydrochemical fingerprint (including δD H2O , δ 18 O H2O , δ 7 Li, δ 11 B, δ 18 O SO4 , and δ 34 S SO4) indistinguishable from long-established confined groundwater that likely reflects a mixture of infiltrated meteoric water with high-sulfate hydrothermal fluids. A comparison of historical hydrochemistry data and patterns of past seismicity suggests that discharge of deep fluids is associated with similar deformation structures to those observed during the Kumamoto earthquake, and that seismic activity plays an important role over historic timescales in delivering the majority of the solutes to the caldera outlet, sustaining fluxes that are amongst the world's highest. This upwelling mechanism might be relevant for other systems too, and could contribute to the over-proportional share of active volcanic areas in global weathering fluxes.

Domaines: Planète et Univers [physics]; Sciences de la Terre; Géochimie

Takahiro Hosono, Jens Hartmann, Pascale Louvat, Thorben Amann, Kirstin E Washington, et al.. Earthquake-induced structural deformations enhance long-term solute fluxes from active volcanic systems. Scientific Reports, 2018, 8, ⟨10.1038/s41598-018-32735-1⟩. ⟨insu-02381520⟩