地磁场包含有丰富的地球内部信息，探索地震孕育过程中地磁的前兆异常，对地震预报具有现实意义。在地震孕育过程中，震源场及较大范围的区域应力场的变化可能伴随着地下电导率的某种变化，从而使变化磁场的感应场产生一定的异常而反映到地磁日变化上来。这种异常日变化一般在 The geomagnetic field contains rich information of the Earth’s interior and exploring the precursory anomaly of the geomagnetic during the process of earthquake gestation, which is of practical significance for earthquake prediction. In the process of earthquake breeding, the change of stress field in the source field and the larger area may be accompanied by some change of underground conductivity, so that the induced field of the changing magnetic field will produce some abnormalities and reflect the diurnal variation of the geomagnetic field. This abnormal change in the general