View article

Molecular hydrogen, H₂, is the key component to link the inorganic lithosphere with the subsurface biosphere. Geochemical and microbiological characterizations of natural hydrothermal fields strongly suggested that H₂ is an important energy source in subsurface microbial ecosystems because of its metabolic versatility. One of the possible sources of H₂ has been considered as earthquakes: mechanoradical reactions on fault surfaces generate H₂ during earthquake faulting. However it is unclear whether faulting can generate abundant H₂ to sustain subsurface chemolithoautotrophic microorganisms, such as methanogens. Here we present the result of high velocity friction experiments aimed to estimate the amount of H₂ generated during earthquakes. Our results show that H₂ generation increases with frictional work (i.e., earthquake magnitude) and that a H₂ concentration of more than 1.1 mol/kg of fluid can be …