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EARTHQUAKE ›› 2019, Vol. 39 ›› Issue (3): 61-70.

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Geochemical Characteristics of Soil Gas in the South-west and North-east Segments of the Tangshan Fault Zone, Northern China

YANG Jiang1, LI Ying1, CHEN Zhi1, SUN Feng-xia1, ZHAO Jian-ming2, LI Jing3, WANG Jiang4   

  1. 1.CEA Key Laboratory of Earthquake Prediction Institute of Earthquake Science, CEA, Beijing 100036, China;
    2.Tangshan Earthquake Station of Earthquake Administration of Hebei Province, Tangshan,Hebei 063021, China;
    3. Institute of disaster prevention, Sanhe 065201, China;
    4.Monitoring Network Center of Earthquake Administration of Hebei Province, Shijiazhuang 050021, China
  • Received:2017-09-01 Online:2019-07-31 Published:2019-08-09

Abstract: We discussed the geochemical characteristics of soil gas Rn and CO2 concentration and the correlation between the spatial variation of soil gas and tectonic activity, based on the measurements of Rn and CO2 concentrations in the south-west (Wanglanzhuang) and north-east (Weifengshan) segments of the Tangshan fault zone. The results show that the concentration range of Rn in Wanglanzhuang and Weifengshan are respectively 691 to 57671 Bq/m3 and 471 to 32739 Bq/m3, while the concentration range of CO2 are respectively 0.17 to 7.21% and 0.08 to 1.71%. The concentrations in these two profiles are higher than the regional background values, which may be caused by the open state of fault in the Tangshan area. The release intensity (KQ) of soil gas in these two profiles is different. KQ of Rn and CO2 is 2.90 and 4.04 respectively in Wanglanzhuang Profile, and is 0.90、0.99 respectively in Weifengshan Profile. This illustrates that the concentration in the middle part of Weifengshan Profile is much higher than that at the both ends, while in Weifengshan Profile, the concentration of each part is consistent. The soil gas geochemical results show that the variations of soil gas spatial distribution may be attributed to the different degree of fault fragmentation in the profiles. The higher the regional stress, the higher the fault activity and the concentrations of Rn in Weifengshan Profile. This indicates that the concentration of Rn is closely related to the activity of faults.

Key words: Tangshan fault, Soil gas, Rn and CO2, Geochemistry, Active fault

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