Abstract: :In this paper, the authors analyzed subsurface fluid physical, chemical and CO₂′s precursory anomalies, including near and outside epicenter region, two Yanjin M5.1 earthquakes occurred in the Northeast Yunnan region on July 22 and August 25, 2006. At the same time, the authors also summarized the characteristics of subsurface fluid anomalies. The results show that during the short term, the quantity of subsurface fluid precursory anomalies shows rising trend; during the short term and impending stage, macro anomalies near epicenter region are distributed within 120km range. The distribution of anomalies shows a phenomenon of variation and centrality within 180km range, and anomalies appear more. At two sites CO₂ shows medium term anomalies, while in short term turning rate become large. Therefore, in the impending stage, the accord integration analysis of micro and macro anomalies is important to improve the forecast ability.

Key words: Subsurface fluid, Precursory, Anomaly characteristics, Yanjin earthquake