关键词: 地震前兆异常, 井水位, 中期, 中短期, 从属函数

Abstract: Based on careful selection of underground fluid observation wells(springs),and using the monthly means and subordinate function method,we select the precursory anomalies information of underground water level before the moderately strong earthquakes in Hainan and its vicinity from these wells(springs)and analyze the characteristics of these precursory anomalies.Anomalies in water level are categorized into two classes: ascending medium term anomalies and descending medium-short term anomalies.Statistics show that the average time of medium-short term anomalies in subordinate function is approximately one year before the earthquake,which can be used as reference time index for mid and short term earthquake prediction in this area.

Key words: earthquake precursor anomalies, well water level, medium term, medium-short term, subordinate function