SPACE-TEMPORAL VARIATIONS OF SEISMICITY UNDER IMPACTS OF POWERFULL ELECTROMAGNETIC PULSES

"High energy electromagnetic pulses give rise to an appreciable increase in the rate of local earthquakes, occurring some 2-6 days after the pulses"

by N. Tarasov

Joint Institute of Physics of the Earth of Russian Academy of Sciences,
B. Gruzinskaya, 10, Moscow, Russia, E-mail: tarasov@geodep.ras.ru

The effect of 114 high-energy (1.2-23.1 MJ) electromagnetic pulses emitted by MHD generator, used as source for deep electrical sounding of the crust on the seismicity of the North Tien Shan and adjacent areas in 1983 to 1990 is examined. The trigged seismicity were identified upon the background of the natural variation by the coherent summation of earthquakes in time windows of 20 days about the time of each MHD - generator start-up.

It was shown high energy electromagnetic pulses give rise to an appreciable increase in the rate of local earthquakes, occurring some 2-6 days after the pulses. The spatial variations of the total seismic energy changes after MHD - generator start-up demonstrates that seismic energy release increasing takes place within a number relatively small zones located predominantly in southern part of the area which belong to the crystalline rocks of the North Tien Shan. Electromagnetic impacts causes increase of seismic energy release basically in most active zones.

Total earthquakes energy released in the area during 20 days after all start-ups was 2.03.1015 J greater than the energy released for a period of the same length before them, the bulk of the release bing due to the earthquakes occurring in the upper 5-km layer. At the same time, the total energy transmitted by MHD - generator to the radiating dipole for all start-ups was 1.1.109 J, i.e. six orders of magnitude smaller. Consequently, the high energy electromagnetic pulses initiated the release of the energy that had been stored in the crust due to other sources.

Based on the consideration of energy balance to be preserved in the crust, it can be conjectured that a man-induced increase in the ratio of seismic energy radiated in the form of small earthquakes leads to an additional release of tectonic stresses, thereby diminishing the likelihood of catastrophic events.