Study of the EM responses under shock impacts on rock samples. III. Power industrial explosions

Abstract

The problem of the electromagnetic (EM) responses at mechanical shock impacts on rocks of various structure and composition caused by the powerful industrial explosions is studied experimentally. This part of the paper is a logical prolongation of previous laboratory and field experimental investigations described in Parts I and II, and presents the results of field investigations obtained on real geological objects on studying the structure and intensity of the EM responses generated in the ELF-VLF frequency range in dependence on a character and power (energetic characteristics) of seismic impact. In the investigations both the seismo-electromagnetic and the radio-impulse methods realized in the field experimental complex were used. At the explosive impacts on rocks and ore bodies at distances of 100-200 m from the point of explosion, the intense signals in the ELF (1-30 Hz) and VLF (1-20 kHz) frequency ranges were registered in the experiments, and the cause of this was the piezoelectric effect, arising as a result of the impact of a shock wave to quartz inclusions in rocks. Studies have shown that similar responses in the ELF and VLF ranges can be observed (in the presence of quartz-containing ore bodies) at natural seismic events - the earthquakes of the 9-13 energetic class. The results obtained are in good agreement with our previous ones obtained in laboratory and field experiments and presented in the Parts I and II of the work. Besides of registration of the seismic responses in the EM field, the results obtained can also be useful when performing direction finding works to ore deposits using spatially diversited ELF-VLF receiving stations.