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震磁效应信息的提取是在强干扰的背景上进行的,按现在的认识,震磁效应是微弱的。因此,在判断震磁效应信息之前,除了要弄清楚变化场的背景规律外,还须弄清楚基本场长期变化的时空分布特征。 本文采用我国及其邻近地区1955—78年50个地磁台站三要素(磁偏角D,水平强度H和垂直分量Z)实测年均值资料,用“按距离加权最小二乘曲面拟合”法,计算、绘制并分析研究了北纬10°—64°、东经75°—153°这一区域内地磁场各要素(D,H,Z等)长期变化的时空分布特征。结果表明: 1)长期变化有大尺度的区域性差异,如垂直分量Z的等变线1965,0年代以前在我国南部出现了由下降转为上升的转折,其它地区仍在下降。1975,0年代转折移动至华北南部,1978,0年代整个中国地区都现生了转折。同样,其它要素亦有类似的时空分布特征。 2)我国地球磁分布比较均匀,表现出受东亚大陆磁异常控制的整体性特征。 3)“按距离加权最小二乘曲面拟合”法,不仅适用于较大的区域,而且有较高的拟合精度,具有实际应用价值。
The extraction of seismic magnetic effect information is carried out on the background of strong interference. According to the present understanding, the seismic magnetic effect is weak. Therefore, before judging the information of seismic effect, in addition to clarifying the background law of the changing field, the temporal and spatial distribution characteristics of long-term changes of the basic field must also be clarified. In this paper, the annual average data of three elements (declination D, horizontal intensity H and vertical component Z) of 50 geomagnetic stations in China and its adjacent areas from 1955 to 1978 were used. According to the method of “least square fitting by distance weighted” , Calculated, plotted and analyzed the temporal and spatial distribution characteristics of long-term variation of each element (D, H, Z, etc.) in the region from 10 ° -64 ° North latitude and 75 ° -153 ° East longitude. The results show that: 1) There are large-scale regional differences in long-term changes, such as the isotropic variation of the vertical component Z in 1965, a transition from decline to rise in the southern part of China before the 0’s, and the decline in other regions. The turning in 1975 and the 1980s shifted to the south of North China, and a turning point came to an end in 1978 and the whole of China. Similarly, other elements have similar spatial and temporal distributions. 2) The earth’s magnetic distribution in China is relatively uniform, showing the holistic characteristics controlled by the magnetic anomalies in the East Asia continent. 3) “The method of distance-weighted least-squares surface fitting” not only applies to large area, but also has higher fitting accuracy and has practical application value.