Abstract: The precursory anomaly of an earthquake can provide some precursory information, such as anomaly spot, anomaly variable, anomaly duration, and validated time after anomaly occurrence. All these clues define the precursory anomaly information variable, S-value to describe the earthquake anomaly. Based on the synthetic math expression of earthquake precursory anomaly information variable in this paper, by using some data processing methods, including the smooth filter canceled cycle, trend item and membership functions, we acquired the S-values according to the information provided by 22 main seismic stations in Liaoning area. Analyzing these S-values, we conclude that before 12 earthquakes with M_L≥5.0 in Liaoning Province and its neighboring area (37~44°N, 117~127°E). S-value scheduling curve will present anomalous peak values (S≥0.12) in some degrees. It means that within 6 months of S-value peak, the earthquake (M_L≥5.0) will happen in Liaoning. The spatial scanning of S-value also shows us that anomaly peaks are focused around the seismic epicenter, and earthquake will happen in a scope of 150 km around the epicenter.

Key words: Membership function, Spatial scanning, S-value, Precursory anomaly