Purpose. It is well-known that strong earthquakes are typically accompanied by some phenomena which relate to variations of natural electromagnetic fields. Based on the idea about the mechanism of lithosphere–atmosphere–ionosphere coupling we expect to detect some precursors of strong natural earthquakes in electromagnetic data sets recorded by magnetotelluric instruments far enough from epicenters.
The earthquakes monitoring in all world reveals that the “seismogenic” fluctuations of magnetic field in wide frequency band often occur before these seismic events. We believe that the most reliable information is concentrated in ultra low frequency (ULF) band (0.001-3 Hz). The earthquake ULF magnetic precursors of lithospheric origin are very weak as a rule and their frequency range is overlapping with signals of ionospheric origin. The new method of the seismomagnetic signals selection at the background of more powerful magnetic variations of other nature is proposed.