提取地震前的地磁异常,排除外空场的影响是很重要的。就地磁“变化场”而言,它包括“内场”和“外场”二个部分,其中“内场”主要是“外场”作用于地球内部而产生的感应磁场,其量约占总变化场的三分之一。对于相距几百公里的两个地磁台而言,可以认为外空场对于它们的影响是一致的。但由于各台台址的地下构造和电导率不相同,使得同一外空场变化对它们产生的感应场增量不一。江苏处于中、低纬度地区,地磁总强度主要 It is very important to extract the geomagnetic anomalies before the earthquake and eliminate the influence of the outer space. In terms of geomagnetic “change field”, it includes two parts: “inner field” and “outer field”, in which “inner field” is mainly the induced magnetic field generated by “outer field” One-third of the time. For two geomagnetic stations hundreds of kilometers apart, one can consider the effect of the outer space on them to be consistent. However, due to the different subsurface structures and conductivities of the stations, the changes of the same outer field have different increment of the induced fields. Jiangsu is located in the middle and low latitudes, the main geomagnetic total strength