Analysis of a Possibility of Electromagnetic Earthquake Triggering by Ionospheric Disturbations

It is well known that some ionospheric perturbations precede strong earthquakes, and there are attempts to detect and apply them as precursors for short-term earthquake prediction. In that case it is assumed that the processes of earthquake preparation in lithosphere can provide disturbances in ionosphere. From another hand, theoretical, field, and laboratory experimental results obtained during implementation of research projects in Russia within recent ten years demonstrated an evidence of artificial electromagnetic triggering of earthquakes, when electric current density provided by special pulsed power systems at the earthquake source depth (5-10 km) is 10^-7 - 10^-8 A/m^2 is comparable with the density of telluric currents induced in the crust by ionospheric disturbances. In this case it may be supposed that some reported preseismic ionosperic anomalies provide triggering effect for earthquake occurrence. To clear the details of ionosphere-lithosphere coupling and a possibility of electromagnetic triggering of seismic events an analysis of ionospheric precursors of earthquakes, statistical analysis of geomagnetic field variations and seismic activity, laboratory studies of dynamics of deformation of stressed rocks under the electromagnetic impact, as well as theoretical analysis of the possible mechanisms of interaction of rocks with electromagnetic field and their verification in laboratory experiments at the special test equipment, which simulates behavior of the fault zone under external triggering factors were catrried out. A model of electromagnetic triggering of seismic events caused by ionospheric electromagnetic perturbations is proposed based on the fluid migration to the fault under critical stressed state due to interaction of conductive fluid with telluric currents and geomagnetic field. A possibility of development of physical method of short-term earthquake prediction based on electromagnetic triggering effects is discussed.