Persistent CO$_2$ emissions and hydrothermal unrest following the 2015 earthquake in Nepal
Résumé
Fluid–earthquake interplay, as evidenced by aftershock distributions or earthquake-induced effects on near-surface aquifers, has suggested that earthquakes dynamically affect permeability of the Earth’s crust. The connection between the mid-crust and the surface was further supported by instances of carbon dioxide (CO$_2$) emissions associated with seismic activity, so far only observed in magmatic context. Here we report spectacular non-volcanic CO$_2$ emissions and hydrothermal disturbances at the front of the Nepal Himalayas following the deadly 25 April 2015 Gorkha earthquake (moment magnitude M$_w$ = 7.8). The data show unambiguously the appearance, after the earthquake, sometimes with a delay of several months, of CO$_2$ emissions at several sites separated by > 10 kilometres, associated with persistent changes in hydrothermal discharges, including a complete cessation. These observations reveal that Himalayan hydrothermal systems are sensitive to co- and post- seismic deformation, leading to non-stationary release of metamorphic CO$_2$ from active orogens. Possible pre-seismic effects need further confirmation
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