Abstract: The paper discusses the relationship between distribution characteristics of precursory mercury anomalies and those of regional tectonics in the mainland of China on the basis of data of earthquakes ( ME≥ 6) and mercury anomalies in the different tectonical stress field. It is found that the spatial features of mercury are correlated not only with the magnitude of earthquakes, distance from epicenter to the observational site, but also the stress field and medium between the focus and the observational site. It shows obviously that the different mercury anomalies occurred in different stress fields before the earthquakes. Mercury anomalies found in the Northern China are shorter in the period and smaller in spatial. extent, but those found in the Northwestern China are usually farther from the epicenter and last for a longer period, and those found in Southwestern China are generally for a larger felt extent.

Key words: Tectonical stress field, Earthquake activity, Mercury anomaly