水位前兆异常特征分析

Statistic and Analysis on Precursory Anomalies of Water Level

以正式出版的《中国震例》（1966-2006年）资料为基础，选取肘≥5．0地震的水位异常数据，分别从水位异常形态、异常数量、异常幅度、震中距分布、异常时间、震级等方面进行分析，发现所有震例中，水位上升形态最多，占43．82％；震级越大，水位平均异常数量越多；在渐变幅度≥3．0cm、突变幅度≥0．5cm、破年变幅度≤70％或≥120％的情况下，可初步判定为水位前兆异常；震级越大，水位异常范围越广；地震前水位异常集中爆发的时间越长，距离震中越远。地震孕育进入短临阶段的水位异常特征如下：云南和川滇地区在震前50-75天时，水位异常数量突然减小，之后增加；西北地区从震前75天开始，水位异常数量减少；其它地区从震前50天开始，水位异常数量急剧增加；从全国整体来看，在震前100天后，水位异常数量逐渐增加。

Based on ＂Earthquake Cases in China＂ which was formally published from 1966 to 2006, we selected the water level precursory anomalies data of M ≥ 5.0 earthquakes, and analyzed the anomaly shape, anomaly a- mount, anomaly amplitude and anomaly time of water level, epicenter distance distribution, and magnitude etc.. We found that the amount of rising pattern of water level which was the most accounted for 43.82%, and the higher the magnitude was, the more the amount of water level anomaly was. When the gradient amplitude of wa- ter level was more than 3.0 cm, the mutation amplitude was more than 0. 5 cm, and the amplitude of broken an- nual variation was no more than 70% or no less than 120% , we could judge it as the precursory anomalies of water level. The higher the magnitude was, the wider range of the water level anomaly was. The longer the time of water level anomaly concentrated appeared before the earthquake, the longer the distance of water level anom- aly from the epicenter was. The characteristic of the earthquake preparation which was going into shorten and im- pending earthquake stage shows as follow ： the amount of water level anomaly decreased suddenly in Yunnan and Sichuan-Yunnan area from 50 to 75 days before the earthquake, then increased. The amount of water level a- nomaly decreased in 75 days before the earthquake in northwest area of Yunnan, and increased sharply in 50 days before the earthquake in other area, and it increased gradually in 100 days before the earthquake in China.