CO diffusive emission in the co-seismic rupture zone of the Wenchuan M_S 8.0 earthquake

Abstract

Carbon monoxide (CO) is one of the most important components in the troposphere, which plays a significant role in the oxidation and reduction chemistry of the atmosphere. Surface rupture zones are one of the main regions of gas degassing. The Wenchuan M_S 8.0 earthquake produced the ~240-km-long Yingxiu-Shuiguan rupture zone and the ~72-km-long Tongji-Hanwang rupture zone. In this study, soil CO flux in the surface rupture zones produced by the Wenchuan M_S 8.0 earthquake (WSRZ) was measured using the closed-chamber method. The results showed that soil CO flux in the WSRZ ranged from 0.2 to 25.4 mg m⁻² d⁻¹ with background value of 5.2 mg m⁻² d⁻¹, which indicated gas was still degassing after the Wenchuan M_S 8.0 earthquake. Abiogenic CO in the WSRZ might origin from the low crust flow and chemical reactions of the C-H-O fluids in the active fault zone. The spatial variations of CO fluxes along the WSRZ show significant segmentation characteristics. This research implicates the geochemical characteristics and origin of CO from natural fault zones as well as provides basic data for geochemical characteristics of soil CO degassing in co-seismic surface rupture zones.