Abstract: The capital circle region is one of the special areas for monitoring seismicity and prevention of seismic disaster in China, and is an important test area for earthquake monitoring and prediction study, where a lot of seismic fluid geochemistry researches have been done and plentiful results have been gained. This work has made an important contribution to earthquake prediction research. The authors studied the regional features of some geochemical components. The results show that under normal condition, the background values of radon, mercury and hydrogen in ground water are lower and the variation amplitudes are relatively small, while the measured values of the components at most stations become higher when seismicity is active in the region. This can be used as an index for short-term earthquake prediction.

Key words: Earthquake prediction, Capital circle region, Gas geochemistry, Regional characteristics