Abstract
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 (CO2) emissions associated with seismic activity, so far only observed in magmatic context. Here we report spectacular non-volcanic CO2 emissions and hydrothermal disturbances at the front of the Nepal Himalayas following the deadly 25 April 2015 Gorkha earthquake (moment magnitude Mw = 7.8). The data show unambiguously the appearance, after the earthquake, sometimes with a delay of several months, of CO2 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 CO2 from active orogens. Possible pre-seismic effects need further confirmation.
Highlights
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
We report spectacular outbursts of CO2 and hydrothermal disturbances at several sites in Central Nepal separated by >10 kilometres that have been triggered by the 2015 Gorkha earthquake
Outbursts of CO2 triggered by the Gorkha earthquake
Summary
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. Carbon dioxide (CO2) emissions were observed in association with seismicity in the case of the Matsushiro swarm[9] in Japan or, recently, at the Lassen volcano[22] (Cascades Range, USA) and in the Eger Rift[23] (Czech Republic), which suggests connection between the mid-crust and the ground surface through gas transport Such examples so far were only observed in the presence of magmatic activity. The seasonal and yearly stability of the soil–gas radon concentration time-series[34,35], the invariant radon–CO2 fluxes relationship[30,36], and the results of watering experiments[36] at selected sites attest to the remarkable temporal stability of these hydrothermal systems, even during monsoon These non-volcanic CO2 emissions are characterised by radiogenic helium, high radon content, and carbon isotopic compositions suggesting metamorphic CO2 production at >5 kilometres depth[30,31,32,34]. It partly ruptured the MHT along a 120-kilometre-long segment east from the epicentre[41], whose northern limit coincides with the
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