龙岩地震台地倾斜观测数据降雨干扰及福建中强地震前异常分析

Rainfall interference of ground tilt observation data at Longyan Seismic Station and analysis of anomalies before moderate strong earthquakes in Fujian

龙岩地震台垂直摆倾斜仪受降雨干扰严重,人为延迟降雨发生时间,研究观测值与降雨量累积值之间的相关系数,认为将降雨时间人为延迟13天,二者相关性较好,利用一元线性回归方法剔除降雨干扰,数据预处理效果更理想。使用剔除降雨干扰的观测数据,基于曲线形态、二阶差分求加速度、矢量图等手段,分析福建几次中强地震前龙岩地震台倾斜观测数据变化特征,研究数据异常与中强震的关系,结果发现:在福建中强地震发生前1年内,龙岩地震台垂直摆倾斜仪NS、EW分量与降雨量累积值(降雨人为延迟13天)的残差值曲线,均出现超出或达到2倍中误差现象,且临震前几天到几个月,残差值曲线多出现转折现象;中强震发生前2—8个月,NS、EW分量日均值二阶差分求加速度值曲线,均有超2倍中误差现象。

The vertical pendulum tiltmeter at Longyan Seismic Station is seriously interfered by rainfall.Studying the correlation coefficient between the observed values and the accumulated rainfall values by artificially delaying the rainfall occurrence time shows that dallying the rainfall time by 13 days can get a goodcorrelation between the two.Eliminating the rainfall interference by using the monadic linear regression method can get a better data preprocessing effect.Using the observation data excluding rainfall interference,based on curve shape,second-order difference to calculate acceleration,vector map,and other means,the variation characteristics of tilt observation data at Longyan Seismic Station before several moderate strong earthquakes in Fujian Province were analyzed and the relationship between data anomalies and moderate strong earthquakes was studied.The results showed that,within one year before the occurrence of moderate strong earthquakes in Fujian,the difference curves between the NS and EW components of the vertical pendulum tiltmeter observations at the Longyan Seismic Station and cumulative rainfall values(artificially delayed by 13 days)exceeded or reached 2 times of the mean square errors,and the residual curvesturned several times a few days to months before the earthquakes.Two to eight months before the occurrence of moderate and strong earthquakes,the second-order difference derived acceleration value curves of NS and EW components’daily mean value exceed twice the mean square errors.