Abstract: Water level observation data can be influenced by various factors or be caused by complicated reasons, therefore, research on the causesof abnormity is of significant importance in terms of the earthquake prediction accuracy. In this paper, we give a systematic analysis of the water level changes of Huoshan 33 well in Anhui province since 1998 and a detailed investigation of the environmental influences on the water level changes. Further comparative experiments with the observation system show that the environmental influences scarcely affect the water level, whereas the observation system proves to be a non-negligible factor that may have a profound effect on the water level observation. Through the study in the paper, we have made beneficial efforts to enhance the quality of observation data and obtain more reliable earthquake precursory signals by eliminating interferences.

Key words: Water level change, Observation system, Cause of abnormality, Huoshan 33 well