Response of the Beiwenquan hot spring’s hydrochemical features in Chongqing to the Wenchuan earthquake of magnitude 8.0 in Sichuan

The Beiwenquan hot springs were continuously monitored from May 1 to July 4, 2008. It proves that the temperature and discharge as well as hydrochemistry have obvious response to the earthquake of magnitude 8.0 in Wenchuan. (1) After the earthquake, temperature of these springs all dropped about 1℃. (2) Three higher elevation springs BWQ-2,BWQ-3,BWQ-4 ceased to flow, but BWQ-1, being located lower, increased its discharge by nearly 50%, and BWQ-6's discharge also increased.(3) Concentration of K+, Na+, Ca2+ in those lower located hot springs reduced after the earthquake and has excellent linear correlation with the earthquake. But concentration of Mg2+ increased. Concentration of Fe2+, Mn2+ increased several fold on May 12 and decreased gradually thereafter. On July 4, the Concentration of Fe3+, Mn2+ was the same with May 1. Concentration of SO42-, F- changed anomalously. It is believed that the variation of physicochemical properties in hot springs results from the mixture of cold waters from surface or from overlying aquifer mixed with the hot water of the spring because the fractures connected the upper or overlying aquifer with the hot spring after the earthquake.