Seismomagnetic effect is due to the piezomagnetic effect or magnetostriction of some materials. Therefore, it is believed that not only the change of geomagnetic field will occur in local areas after the occurrence of a large earthquake, but also before the occurrence of a large earthquake, due to the different squeezing or different temperature effects of materials, the magnetic properties of materials will also be changed and reflected as the abnormal change of local geomagnetic field.
Therefore, it is possible to predict large earthquakes by using this change. Others believe that the preparation, occurrence and development of earthquakes are related to the change of local geomagnetic field, and this connection is collectively called seismomagnetic effect. In order to make use of seismomagnetic effect, it is necessary to eliminate the influence of outer space current system changes on the geomagnetic field. At present, the method of subtracting data from two or more geomagnetic stations (selected according to different magnetic longitude or latitude) is mostly used to extract the "information" of seismomagnetic effect and analyze and predict earthquakes.
