Geochemistry of soil gas in the seismic fault zone produced by the Wenchuan Ms 8.0 earthquake, southwestern China

• Published in: Geochemical transactions GT 2010-12, Vol.11 (1), p.5-5, Article 5
• Main Authors: Zhou, Xiaocheng, Du, Jianguo, Chen, Zhi, Cheng, Jianwu, Tang, Yi, Yang, Liming, Xie, Chao, Cui, Yueju, Liu, Lei, Yi, Li, Yang, Panxin, Li, Ying
• Format: Article
• Language: English
• Subjects: Earth and Environmental Science; Earth Sciences; Environmental Chemistry; Geochemistry; Research Article
• ISSN: 1467-4866; 1467-4866
• DOI: 10.1186/1467-4866-11-5

The spatio-temporal variations of soil gas in the seismic fault zone produced by the 12 May 2008 Wenchuan M s 8.0 earthquake were investigated based on the field measurements of soil gas concentrations after the main shock. Concentrations of He, H 2 , CO 2 , CH 4 , O 2 , N 2 , Rn, and Hg in soil gas were measured in the field at eight short profiles across the seismic rupture zone in June and December 2008 and July 2009. Soil-gas concentrations of more than 800 sampling sites were obtained. The data showed that the magnitudes of the He and H 2 anomalies of three surveys declined significantly with decreasing strength of the aftershocks with time. The maximum concentrations of He and H 2 (40 and 279.4 ppm, respectively) were found in three replicates at the south part of the rupture zone close to the epicenter. The spatio-temporal variations of CO 2 , Rn, and Hg concentrations differed obviously between the north and south parts of the fault zone. The maximum He and H 2 concentrations in Jun 2008 occurred near the parts of the rupture zone where vertical displacements were larger. The anomalies of He, H 2 , CO 2 , Rn, and Hg concentrations could be related to the variation in the regional stress field and the aftershock activity.