Hydrochemical characteristics of hot spring waters in the Kangding district related to the Lushan M_S = 7.0 earthquake in Sichuan, China

Abstract. Hydrogeochemistry of 10 hot springs in the Kangding district was investigated by analyzing cation and anion concentrations in the spring water. The water samples were collected in the 5 days after the Lushan M_S = 7.0 earthquake, which occurred on 20 April 2013. The spring waters are classified into seven chemical types based on their hydrochemical compositions. Compared with hydrochemical data before the Lushan earthquake, concentrations of Ca²⁺, HCO₃^- and total dissolved solid (TDS) in water samples from the Guanding, Erdaoqiao, Gonghe, Erhaoying, Tianwanhe and Caoke springs significantly increased, which may be the result of a greater increase in groundwater from carbonate rocks, and water–carbonate rock interactions, enhanced by the increment of CO₂. Concentrations of Na⁺, Cl^- and SO₄^2- in water samples from the Guanding, Zheduotang, Xinxing and Gonghe springs decreased, indicating a dilution of shallow waters. Concentrations of Na⁺ and SO₄^2- in water samples from the Erhaoying spring water increased, which may be attributed to water–granite interactions enhanced by H₂S. The results indicated that hydrochemical components of spring water could be used as an effective indicator for earthquakes.