Abstract: Using telluric field minute values of EW and NS directions at Pingliang station, the vector synthesis results show that the telluric field intensity and direction variations were characterized by daily period. The direction is consistent with the rock cracks (α angle) of the preferred orientation calculated with tidal harmonic amplitudes. At this site, magnetic storm interferences from space have little effect on the calculation results of α. The typical interferences of pulse, manual power supply of resistivity observation and subway were simulated and analyzed. The results show that the calculations of α are unaffected, basically, when the disturbance amplitudes are less than the peak values of diurnal variation at Pingliang station. When direct current step disturbance was added, the calculation of α is affected on the same day, but no longer affected from the second day.

Key words: Geoelectric field, Typical interferences, Preferred orientation of cracks