Abstract: A fast measurement method is introduced here for measuring CO₂ in fault gas. The characteristics of CO₂ precursory anomalies, which were observed in 9 earthquakes (M≥4) in Houhaoyao, Huailai county for last 7 years, are analyzed. Forty-seven days before the Zhangbei-Shangyi earthquake, an anomaly of abrupt increase in CO₂ in fault gas was observed. The peek value of CO₂ is about 10 times as the background value. Based upon the above-mentioned result, a relatively accurate short-term and impending prediction for the earthquake was made 12 days before it.

Key words: Fault product gas, Precursory anomaly, Short-term and impending prediction, Zhangbei-Shangyi earthquake, Fast measurement method for co₂