Investigation of EM Responses Under Shock Impact on Rock Samples. I. Laboratory Experiments.

Abstract

The problem of the electromagnetic responses at mechanical shock impacts on rock samples of various structure and composition is studied experimentally. This part presents the results of laboratory investigations in the ULF and VLF frequency ranges with use of the experimental complex specially developed. The possibility of the occurrence of pulsed electrical signals excited by mechanical impacts is shown. It was found that, at least for rocks containing crystalline quartz, such impacts excite low-frequency signals caused by the piezoelectric effect. It was also shown that upon sample destruction, radio-pulse signals are generated. It was noted that when impacted on samples of other quartz-containing rocks (granite, mudstone, siltstone), similar responses are also observed, but their level is 3 - 10 times lower. The results obtained can be considered as some ideological premise for explaining the nature of some radiophysical precursors that are observed both directly in the earthquake preparation zone and are manifested in ionospheric processes. A description of the experiments and obtained results on studying the structure of EM emissions generated by shock and explosive impacts on large monolithic blocks of rocks of complex structure will be presented in the next parts of the work.