Possible mechanisms of co-seismic electromagnetic effect

Abstract

We analyze theoretically two possible sources of co-seismic electromagnetic response to the propagation of various types of seismic waves caused either by the electrokinetic phenomena or geomagnetic inductive effect. The differences between these two generation mechanisms have been examined for different types of seismic waves (P, S, and Rayleigh-Love). Theoretical relationships describing the dependence of the co-seismic signal amplitude, polarization and apparent impedance on the earthquake seismic moment and magnitude have been derived as a function of distance. We indicate an observational possibility to discriminate seismo-electrokinetic and seismo-magnetic effects and to estimate their contribution into a recorded co-seismic electromagnetic signal. Magnitudes and polarization of these signals are shown to depend strongly on the type of seismic wave and local crust parameters, such as streaming potential coupling coefficient, conductivity, inhomogeneity, etc. Co-seismic electromagnetic signals, though not directly applied for earthquake prediction, contain a useful information on local crustal phenomena, and can be used to identify ''sensitive'' zones perspective for the monitoring of precursory electromagnetic disturbances.

Seismoelectric effect in Lamb’s problem

“…The co-seismic electromagnetic variations are usually observed during the passage of seismic waves through the ground-based magnetometers and antennas or buried electrodes [Ivanov, 1940;Martner and Sparks, 1959;Eleman, 1965;Anisimov et al, 1985;Iyemori et al, 1996]. There are two basic physical mechanisms of these coseismic phenomena: the seismoelectric effect in porous water-saturated media and the perturbation of the Earth's magnetic field due to the motion of the conductive ground [Surkov et al, 2018]. The seismoelectric effect builds up as a result of electric charge separation caused by the electro-chemical processes in the electrolyte solution, which is contained in the underground fluid [Frenkel, 1944].…”

“…This means that the acoustic variables contained in the second set play the role of known sources of seismoelectric variations. The seismoelectric effect has been studied in more detail for the case of a harmonic acoustic wave propagating in an infinite homogeneous space [e.g., Surkov et al, 2018]. More complex models of the seismic source are necessary in order to study the seismoelectric phenomenon associated with earthquake and explosion.…”

“…However, in practice, it is difficult to conclude unambiguously which of those mechanisms prevails because of a large variability of the realistic crust parameters, such as porosity, permeability, conductivity and etc. [Surkov et al 2018].…”

Electromagnetic disturbances induced by nuclear tests in North Korea

“…In the previous studies, the correlation between electromagnetic observations and seismic waves have been investigated widely (Hu and Gao 2011;Gao et al 2014;Surkov et al 2018). Taking the different fracture mechanisms of explosions with the natural earthquakes into account, a digital simulation has been performed for understanding the strong response observed in the geomagnetic field measured in northeast China.…”

“…Gao et al (2014) studied the properties of EM signals generated by an earthquake due to the motional induction effect, i.e., from the motion of the conducting crust across the Earth's magnetic field, and they demonstrated that the motional effect dominated the mechanoelectric conversion under low frequency and high conductivity conditions. Surkov et al (2018) discussed the co-seismic electromagnetic effects, including the electrokinetic and geomagnetic inductive effect. Their results illustrated that the magnitude and polarization of the co-seismic electromagnetic signals depended strongly on the type of the seismic wave and the local crust parameters such as the streaming potential coupling coefficient, conductivity, inhomogeneity, etc.…”