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.
Geoacoustic emission, electromagnetic impact, electrical double layers, fluid, borehole, earthquake, physical mechanism
1. Alad'ev, The regularities of the acoustic emission in the samples of geomaterials tested for creep under energy loading by physical fields, Problems of Seismology in the Third Millennium, 2003.
2. Antropov, Theoretical Electrochemistry, 1984.
3. Bogomolov, Acoustic emission response of rocks to electric power action as seismic-electric effect manifestation, // Ann. Geophysics, v. 47, no. 1, 2004.
4. Damaskin, Electrochemistry, 1987.
5. Gavrilov, Physical causes of diurnal variations in the geoacoustic emission level, // Dokl. Earth Sci., v. 414, no. 4, 2007., doi: 10.1134/S1028334X07040320
6. Gavrilov, On the method for continuous monitoring the electric resistivity of the rocks, // Seismich. Instr., v. 49, no. 3, 2013.
7. Gavrilov, On the question of the influence of natural electromagnetic fields on the rate of geoacoustic emission, Geophysical Monitoring and Problems of Seismic Safety of the Russian Far East: Proc. Regional Scientific and Technical Conf.,, 2008.
8. Gavrilov, Variations in geoacoustic emissions in a deep borehole and its correlation with seismicity,v Ann. Geophysics, v. 51, no. 5/6, 2008.
9. Gavrilov, Comparison of the geoacoustic measurements in boreholes with the data of laboratory and in-situ experiments on electromagnetic excitation of rocks, // Izv. Phys. Solid Earth., v. 47, no. 11, 2011., doi: 10.1134/S1069351311100041
10. Gavrilov, Variations of geoacoustic emission rate in the deep G-1 borehole Kamchatka and their correlation to seismic activity, // Vulkanol. Seismol., no. 1, 2006.
11. Gavrilov, Modulating impact of electromagnetic radiation on geoacoustic emission of rocks, // Russ. J. Earth Sci., v. 13, 2013., doi: 10.2205/2013ES000527
12. Gavrilov, The physical basis of the effects caused by electromagnetic forcing in the intensity of geoacoustic processes, // Izv. Phys. Solid Earth, v. 50, no. 1, 2014., doi: 10.1134/S1069351314010042
13. Khavroshkin, Some Problems of Nonlinear Seismology, 1999.
14. Khatkevich, Hydrogeochemical studies in Kamchatka associated with searching for the precursors of the earthquakes, // Vulkanol. Seismol., no. 4, 2006.
15. Lutikov, Estimate of the effective radius of the zone controlled by the sources of endogenous microseismic noise, // Vulkanol. Seismol., no. 4, 1992.
16. Mironenko, Dynamics of the Ground Water, 2005.
17. Parkhomenko, Electric Properites of Rocks, 1965.
18. Parkhomenko, Influence of unidirectional pressure on electric resistivity of rocks, // Izv. Akad. Nauk SSSR, Ser. Geofiz., no. 2, 1960.
19. Report, On the prospecting and exploration at the Verkhnyaya Paratunka hydrothermal field, Termal'nyi village, Kamchatka: Paratunskaya hydrogeological expedition of Kamchatka PGO, 1980.
20. Report, On the thermal water drilling at the wildcat G-1 well on the Khlebozavod segment of the Petropavlovskaya area in 1986--1988, 1988.
21. Salem, Theory of Electrical Double Layer, 2003.
22. Simanova, New Handbook of the Chemist and Technologist. Electrode Processes. Chemical Kinetics and Diffusion. Colloidal Chemistry, 2004.
23. Sheimovich, The 1:200 000 State Map of the Russian Federation, South Kamchatka Series. Sheets N-57-XXI Northern Koryaki, N-57XXVII Petropavlovsk-Kamchatsky, N-57-XXXIII Mt. Mutnovsakaya, 2000.
24. Sobolev, Mechanoelectrical Events on the Earth, 1980.
25. Sobolev, Earthquake Physics and Precursors, 2003.
26. Titov, Electrokinetic phenomena in rocks and its application to geoelectrics, Doct. Geol.-Min. Dissertation, 2003.
27. Titov, Time constants of induced polarization in water-saturated sands: theory and experiments, // Russian Geology and Geophysics, v. 42, no. 6, 2001.
28. Vlasov, Telemetric system of the multiinstrumental network for geophysical monitoring, // Seismicheskie Pribory, v. 44, no. 2, 2007.
29. Vsevolozhskii, Basics of Hydrogeology, 2007.
30. Zabarnyi, The results of the prospecting for geothermal resources in Petropavlovsk-Kamchatsky, 1990.
31. Zakupin, The influence of the external electromagnetic field on the activity of acoustic emission in loaded geomaterials, Geodynamics and Geoecological Problems of the High-Mountain Regions, 2003.
32. Zakupin, The study of the electrically triggered variations in the acoustic emission under the deformation of the samples of the geological materials, Extended Abstract of the Cand. Phys.-Math. Dissertation, 2006.