Abstract: 12 wells (springs), using for o digitalized observation of radon (gas radon), have already been built in Beijing-Tianjin-Hebei region. Among them, 8 wells are running. Because the radon value in one of the eight wells is less than limit of detection, there are only 7 wells (springs) that are used for effective observation. After systematically analyzing different the yearly, monthly and daily gas radon dynamic behaviors of 7 wells (springs) in 2004, and evaluating the possibility of precursory anomaly of earthquake's medium-term, short-term and short-impending-term by comparing with water radon, we consider that it is possible to make out the medium-term precursory anomalies which take the yearly regularity break as mark, and it is hard to make out the short-term and short-impending-term precursory anomalies which take step-change and impulse as mark. By analyzing behavior difference between gas radon and water radon in the same well (spring), we find that gas radon is less stable than water radon. It is not propitious to exert efficiency for gas radon in short-term or short-impending-term precursory anomaly monitoring.

Key words: Gas-radon, Behavior characteristics, Monitoring efficiency, Beijing-Tianjin-Hebei region