Gas emission from the Qingzhu River after the 2008 Wenchuan Earthquake, Southwest China

Four gas and six water samples were collected from the Qingzhu River in Qingchuan County, one of the regions affected by the 2008 Ms8.0 giant Wenchuan Earthquake. Gases were discharged soon after the earthquake, but such emissions ceased in October 2008. The predominant gases are CH4, CO2, N-2 and O-2. The N-2, 02 and noble gases are of atmospheric origin. In contrast, the CH4 and CO2 have typical biogenic signatures, with high C-1/(C-2+C-3), delta C-13(CH4) (-56.1 to -56.6 parts per thousand); delta D-CH4 (-328 to 345 parts per thousand); and delta C-13(CO2) (-6.7 to -4.9 parts per thousand). These measurements indicate that the gases are discharged from a shallow reservoir through faults or fractures caused by the earthquake. The discharging gases are significantly distinct from the natural gas fields nearby, suggesting that there are no direct pathways, such as faults or fractures, between the surface and the natural gas reservoir. (C) 2012 Elsevier B.V. All rights reserved.