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

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 MS = 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 SO42- in water samples from the Guanding, Zheduotang, Xinxing and Gonghe springs decreased, indicating a dilution of shallow waters. Concentrations of Na+ and SO42- 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.