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柱坑深井水位年变规律明显,主要受降雨调制,多年来观测资料连续可靠,反映地震信息敏感清晰,与邬Ms5.5级震中相距约80公里。 对该井水位变化与降雨量的关系用最小二乘法进行相关分析,显示出在寻邬Ms5.5级地震前水位约有113天的低值短期异常前兆。异常最低值超出二倍均方差达120毫米。异常开始水位逐渐下降,在震前57天下降到最低值,接着转为回升,在回升的过程中发震,这一异常特征可用含水岩体在应力作用下裂隙演变过程来解释。
The variation law of water level in deep pits and pit wells is obvious, mainly due to rainfall modulation. The observed data are reliable over the years, reflecting the sensitive and clear seismic information and about 80 km away from the epicenter of Ms5.5 magnitude. Correlation analysis between the water level change and rainfall in this well was carried out by the least squares method. It shows that the water level near the Xunwu Ms5.5 earthquake is about 113 days low and short-term anomalous precursors. Abnormal minimums more than twice the mean square error of 120 mm. The anomalous water level gradually decreased and dropped to its lowest level 57 days before the earthquake, then turned to rebound and started to erupt during the rebound. This anomaly can be explained by the evolution of fractures in aquifer under stress.