Complete one or several phases of repeated geomagnetic field surveys in the earthquake epicenter and the adjacent areas. The observation elements may be geomagnetic vectors (total intensity, magnetic declination, magnetic inclination) or only total geomagnetic intensity according to the specific scheme. According to the obtained geomagnetic field measured results, the spatial structure of the lithospheric magnetic field in the earthquake epicenter and the adjacent areas can be obtained. The temporal variation of the lithospheric magnetic field can be obtained with multi-phase measurements.