%0 Journal Article
%T Geochemistry of soil gas in the seismic fault zone produced by the Wenchuan Ms 8.0 earthquake, southwestern China
%A Xiaocheng Zhou
%A Jianguo Du
%A Zhi Chen
%A Jianwu Cheng
%A Yi Tang
%A Liming Yang
%A Chao Xie
%A Yueju Cui
%A Lei Liu
%A Li Yi
%A Panxin Yang
%A Ying Li
%J Geochemical Transactions
%D 2010
%I BioMed Central
%R 10.1186/1467-4866-11-5
%X The MS 8.0 Wenchuan earthquake of 12 May 2008 produced a 285-km long surface rupture zone along the pre-existing Yingxiu-Beichuan, Guanxian-Anxian, and Qingchuan faults, which indicated the faults were reactivated. The maximum thrust slip distance was estimated to be about 10 m, accompanied by 9 m of shortening across the rupture zone [1]. Most of the large aftershocks were distributed in the north and south parts of the Longmenshan fault zone. The dominant focal depths of the aftershocks were between 5 and 20 km, and the depth of the main shock was 16.0 km. The focal depth distribution in some areas was characterized by high-angle westward dipping. The rupture mode of the main shock was characterized by reverse faulting in the south and with a large strike-slip component in the north [2].The spatial and temporal patterns of deep-source gas leakage can be investigated by measuring soil gas in the faulted zones. The variations of soil-gas concentrations can serve as useful tools for monitoring earthquakes. The short-term decrease of helium concentrations in soil gas along the San Andreas Fault in central California was well-correlated with aftershocks [3]. The sudden increase in CO2 and Rn concentrations at the Mari¨¢nsk¨¦ L¨¢zn£¿ fault in the NW Bohemian swarm quake region might indicate an increase of fault permeability caused by stress redistribution, resulting in the opening of migration pathways [4]. Across two fault segments that ruptured during the magnitude 7.5 Landers earthquake in 1992, anomalously high radon concentrations were found in the fractures three weeks after the earthquake [5]. In parts of southeastern Ghana, In the highly faulted area, radon activity up to 115.00 k Bq/m3 was measured, on the contrary in non-faulted areas radon activity was less than 20.00 k Bq m3 [6]. The concentrations of He, Rn, CO2, and N2 in soil gas clearly showed anomalous values along the fault of Hsincheng in the Hsinchu area of Taiwan [7]. High H2 concentrations of up to 3%
%U http://www.geochemicaltransactions.com/content/11/1/5