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地磁变化的空间的不规律性,不能用两台观测值相减的办法完全消除,从而对震磁效应产生干扰。本文以垂直分量为例,分析了日变、日变幅、0点值、12点值和月均值的不规律性,给出两台差值的标准偏差和变化幅度与距离的关系。例如,两台相距600公里时,日变差值的标准偏差为4γ,日变差值一天内的变化幅度10γ以上,这可能给流动磁测造成假的震磁异常。0点值差值的标准偏差和变化幅度稍小,日变幅、12点值和月均值的这些参数较大,它们都可能形成假的震磁异常。本文最后以76年唐山大震为例,分析了地磁变化不规律性的干扰,认为在昌黎台的Z资料上,不能肯定震前两个月和一年多时间里有中、长期震磁异常。
The irregularity of the geomagnetic changing space can not be completely eliminated by subtracting the two observed values, thus interfering with the seismic magnetic effect. Taking the vertical component as an example, this paper analyzes the irregularity of daily variation, daily amplitude, 0 o’clock value, 12 o’clock value and monthly mean value, and gives the relationship between the standard deviation of the two differences and the variation range and distance. For example, the standard deviation of diurnal variation is 4γ and the diurnal variation of diurnal variation is more than 10γ over a distance of 600 km, which may cause fake anomalous seismic anomalies. The standard deviation and variation range of 0-point difference are slightly smaller. These parameters of daily amplitude, 12-point value and monthly mean value are larger, and they all may form fake seismic magnetic anomalies. Finally, taking the Tangshan earthquake of 76 years as an example, this paper analyzes the disturbance of the irregular geomagnetic variation. It is concluded that there is no certainty of the medium- and long-term seismic anomalies in the Chang-tai-tai Z data over the past two months and more than a year .