Earthquakes produce carbon dioxide in crustal faults

Vincent Famin (1) , Satoru Nakashima (2) , Anne-Marie Boullier (3) , Koichiro Fujimoto (4) , Tetsuro Hirono (2)

1 LGSR - Laboratoire GéoSciences Réunion
2 AIST - Geological Survey of Japan
3 LGIT - Laboratoire de Géophysique Interne et Tectonophysique
4 Graduate School of Science, Department of Earth and Space Science

Fourier transform infrared (FTIR) micro-analysis of pseudotachylytes (i.e. friction-induced melts produced by seismic slip) from the Nojima fault (Japan) reveals that earthquakes almost instantaneously expel 99 wt% of the wall rock CO2 content. Carbon is exsolved because it is upersaturated in the friction melts. By extrapolation to a crustal-scale fault rupture, large events such as the M7.2 Kobe earthquake (1995) may yield a total production of 1.8 to 3.4 × 103 tons CO2 within a few seconds. This extraordinary release of CO2 can cause a flash fluid pressure increase in the fault plane, and therefore enhance earthquake slip or trigger aftershocks; it may also explain the anomalous discharge of carbon monitored in nearby fault springs after large earthquakes. Because carbon saturation in silicate melts is pressure-dependent, FTIR can be used as a new tool to constrain the maximum depth of pseudotachylyte formation in exhumed faults.

Keywords: Nojima fault; pseudotachylyte; infrared spectroscopy; fluids; CO2 exsolution; earthquake; slip weakening; Nojima fault.

Domains: Geophysics [physics.geo-ph]

Vincent Famin, Satoru Nakashima, Anne-Marie Boullier, Koichiro Fujimoto, Tetsuro Hirono. Earthquakes produce carbon dioxide in crustal faults. Earth and Planetary Science Letters, 2008, 265 (3-4), pp.487-497. ⟨10.1016/j.epsl.2007.10.041⟩. ⟨insu-00197197⟩