Electrical triggering of earthquakes: results of laboratory experiments at spring-block models

Abstract

Recently published results of field and laboratory experiments on the seismic/acoustic response to injection of direct current (DC) pulses into the Earth crust or stressed rock samples raised a question on a possibility of electrical earthquake triggering. A physical mechanism of the considered phenomenon is not clear yet in view of the very low current density (10 -7 -10 -8 A/m 2 ) generated by the pulsed power systems at the epicenter depth (5-10 km) of local earthquakes occurred just after the current injection. The paper describes results of laboratory ''earthquake'' triggering by DC pulses under conditions of a spring-block model simulated the seismogenic fault. It is experimentally shown that the electric triggering of the laboratory ''earthquake'' (sharp slip of a movable block of the spring-block system) is possible only within a range of subcritical state of the system, when the shear stress between the movable and fixed blocks obtains 0.98-0.99 of its critical value. The threshold of electric triggering action is about 20 A/m 2 that is 7-8 orders of magnitude higher than estimated electric current density for Bishkek test site (Northern Tien Shan, Kirghizia) where the seismic response to the man-made electric action was observed. In this connection, the electric triggering phenomena may be explained by contraction of electric current in the narrow conductive areas of the faults and the corresponding increase in current density or by involving the secondary triggering mechanisms like electromagnetic stimulation of conductive fluid migration into the fault area resulted in decrease in the fault strength properties.

On the Origin of ULF Magnetic Waves Before the Taiwan Chi-Chi 1999 Earthquake

“…Our present results from the study of the precursory physical conditions before the Taiwan 7.7 M w EQ provide evidence that the pre-EQ sub-ULF (<1 min) magnetic wave activity may indicate a potential cause and not the result of tectonic stresses. This hypothesis is consistent with the fact that MHD generators have been used to activate local earthquakes (Pulinets and Boyarchuk, 2004;Sorokin et al, 2012;Novikov et al, 2017). The impact of electrical pulses of DC current injected through emitting dipole into the earth crust on the spatial and temporal distribution of weak seismicity has been confirmed (Tarasova et al, 2000;Tarasova, 2002, 2004;Chelidze et al, 2006).…”

Space weather and earthquakes: possible triggering of seismic activity by strong solar flares

“…It was shown that a response of acoustic emission to electric action characterized crack formations in the sample rises as the sample loading and maximally appears at the stress level of 0.95-0.99 of breaking stress of the geomaterial. The laboratory study of electric triggering of macro events (laboratory "earthquakes") were carried out at simplified slider system [Chelidze et al, 2002] and spring-block model [Novikov et al, 2017] simulated the seismogenic fault. The both experimental facilities are based on the idea that "stick-slip" behavior of the fault is a mechanism of earthquake preparation and occurrence [Brace and Byerlee, 1966].…”

“…correlation analysis for complete data sets, both global and regional) to clear a presence of electromagnetic triggering phenomena resulted from solar flares. The earthquake faults sensitive to electromagnetic impacts should have specific parameters favorable for earthquake triggering by electromagnetic impact, namely, subcritical stress level [Novikov et al, 2017], increased electric conductivity, certain fault orientation [Han et al, 2004] for occurrence of geomagnetically induced currents of specific density required for the earthquake triggering. In many cases these parameters are unknown.…”

“…An idea was discussed on a possible generation of additional stresses in the Earth crust due to the magnetic field variation [Duma and Ruzhin, 2003;Tren'kin, 2015]. In this paper we make an attempt to validate a possibility of earthquake triggering by solar flare based on electromagnetic triggering phenomena recently discovered in the field [Tarasov et al, 1999[Tarasov et al, , 2000Tarasov and Tarasova, 2004;Chelidze et al, 2006] and laboratory [Bogomolov et al, 2004;Avagimov et al, 2006;Lapshin et al, 2016;Chelidze et al, 2002;Novikov et al, 2017] experiments.…”

Earthquake under Control: Is It Feasible?

“…Magnetically induced slipping was demonstrated also by Novikov et al [56] [57]; by using almost the same technique they have shown that the sharp slip of a movable sample on the supporting block occurs as the triggering the artificial, laboratory "earthquake" hand-made by electromagnetic pulses. Extensive experiments with magneto-hydrodynamic generators for many years have also detected correlation between magnetic and seismic events [53] [58].…”