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为了消除 ρs观测资料中的年周期变化 ,对宝坻、塘沽地震台的地电阻率观测资料与台站附近地区的气压、气温、相对湿度、水位及海水水位的同期资料进行了相关处理分析 ,并对地电阻率年周期变化产生的原因进行了分析 ,认为产生地电阻率与气象要素年周期变化的外因是同一源场作用的结果。而地电阻率变化的内因 ,则是基于地下咸水层厚度的改变及地壳应力场的变化。采用最小二乘法由气象参量和水位变化拟合出地电阻率模型值 ,并计算出观测值与拟合值的残差 ,以消除电阻率观测资料中的年周期变化。结果表明 ,近年来华北地区发生的 6级左右地震前 ,在宝坻、塘沽地震台的观测资料中均存在明显的短期前兆异常。
In order to eliminate the annual cycle variation in ρs observation data, the geo-resistivity observation data of Baodi and Tanggu Seismic Stations are processed and analyzed in relation to the same period data of barometric pressure, temperature, relative humidity, water level and seawater level in the vicinity of the station, The reason of the annual variation of earth resistivity is analyzed, and it is considered that the external source of the earth resistivity and the annual variation of meteorological elements are the result of the same source field. The internal cause of the resistivity change is based on the change of the thickness of the brackish groundwater and the change of crustal stress field. The least square method was used to fit the ground resistivity model values from the variation of meteorological parameters and water level and the residuals of the observed and fitted values were calculated to eliminate the annual cycle variation in the resistivity observation data. The results show that there are obvious short-term precursory anomalies in the observation data of Baodi and Tanggu Seismic Stations before the magnitude 6 earthquakes occurred in North China in recent years.