On the mechanism of intensity variations of geoacoustic emission caused under the action of audio-frequency electromagnetic field

Abstract

The physical mechanism is suggested to account for the phenomenon of modulation of the intensity of geoacoustic emission (GAE) by the external electromagnetic field of audio-frequency band, which was previously revealed by the borehole measurements at the Petropavlovsk-Kamchatsky geodynamical testing area. The key role in this mechanism is played by the electrical double layers (EDL) at the interfacial boundaries between the solid and liquid phases in the fluid-saturated medium. The theoretical estimates based on a simple EDL model show that the modulating effect of the weak audio-frequency elecromagnetic fields on the intensity of GAE is due to the variations in the forces of viscous friction between the mobile part of the liquid fluid and the surface of the solid phase of EDL. The variations in the forces of viscous friction occur with the frequency of the external elecromagnetic field and with the amplitude that is proportional to the amplitude of the external elecromagnetic field. On the scale of a macroscopic volume of the geological medium, the periodical decrease in the friction forces facilitates the increase in the number of the acts of motion of the solid phase relative to the liquid fluid under the influence of the acting mechanical stresses. The comparison of the obtained theoretical estimates with the results of multi-year measurements at the Petropavlovsk-Kamchatsky geodynamical testing area demonstrates their close qualitative agreement.