关键词: 模糊集从属函数, 唐山地震, 地下水位

Abstract: By using the method of membership function of fuzzy set, which is also called the direct method of fuzzy recognition, we have collected and analysed the data of ground-water level in more than 30 wells located in the Beijing-Tianjin-Tangshan area before and after the 1976 Tangshan earthquake (M = 7.8). The results obtained show that the long and intermediate-term anomalies of groundwater level in wells before Tangshan earthquake are difficult to discover but the short-term and imminent anomalies can be recognized obviously. Moreover, the more the time is closed to occurrence of great earthquakes, the more wells show underground level anomalies.

Key words: The fuzzy recognition of precursory anomalies, Tangshan earthquake, Groundwater level