A Mass Spectral Method for He/Ar, N_2/Ar Ratio Measurement of Groundwater and Its Application to Monitor Earthquake

A new special spectral equipment has been developed in our laboratory for measuring He/Ar, N_2/Ar ratio of lithosphere gases in groundwater. Its sensitivityfor He is less than 0.1 ppm, the precision is within ± 2%. Hot groundwaterwas measured continually by this equipment at two places in Beijing. Half amonth before the earthquake of 6.1 classss occurred in Xingtai, the He/Ar ratiobegan to increase obviously and went up continually for one week before theearthquake. The maximum volume was 40% higher than the normal, then wendown gradually to normal level.