Stress induced polarization currents and electromagnetic emission from rocks and ionic crystals, accompanying their deformation

Abstract

Part of Special Issue "Precursory phenomena, seismic hazard evaluation and seismo-tectonic electromagnetic effects" Abstract. A crucial question of the scientific community nowadays, concerns the existence of electric signals preceding earthquakes. In order to give a plausible answer to this question, we carried out two kinds of laboratory experiments of uniaxial deformation of ionic crystals and rock samples: a) In the first kind, stress induced polarization currents are detected and recorded. Our experimental results showed not only the existence of stress induced polarization currents before the fracture of the samples, but the possibility of the propagation of these signals, as well, through conductive channels, for distances much longer than the source dimensions. b) In the second, acoustic and electromagnetic signals are detected and recorded in the frequency range from 1 KHz to some MHz. The mechanism of generation of these signals is shown to be different for those emitted from piezoelectric and from non-piezoelectric materials.A plausible model is also suggested, on the compatibility of our laboratory results with the processes occurring in the earth during the earthquake preparatory stage.

RETRACTED ARTICLE: Correlation between acoustic and other forms of energy emissions from fracture phenomena

“…The tests were carried out at the Laboratory of Fracture Mechanics of the Politecnico di Torino, Italy. By subjecting quasi-brittle materials such as granitic rocks to compression tests, for the first time, bursts of neutron emission (NE) during the failure process were observed [1][2][3][4][5], necessarily involving nuclear reactions, besides the well-known acoustic emission (AE) [6][7][8][9][10][11][12][13], and the phenomenon of electromagnetic radiation (EM) [14][15][16][17][18][19], which is highly suggestive of charge redistribution during material failure and at present under investigation.…”

Mechanism of electromagnetic emission in plastically deformed ionic crystals

“…46 the electromagnetic emission during crack opening in an ionic crystal was studied. In a set of experiments, [47][48][49][50] using high-resolution recording equipment, simultaneous registration of AE and EME was performed on LiF samples under uniaxial compression with a relatively high deformation rate. So it was made possible not only to record the pattern of individual EME pulses 48 but also to detect each acoustic pulse corresponding to a given electromagnetic event.…”

“…So it was made possible not only to record the pattern of individual EME pulses 48 but also to detect each acoustic pulse corresponding to a given electromagnetic event. [47][48][49][50] Thus, it was experimentally proved that the same dynamic structure transformations are sources of both observed EME and AE.…”

Experimental evidence of the compatibility of the cumulative electromagnetic energy release data, with the hierarchical models for the catastrophic fracturing process

“…The question now arises whether these theoretical models can be verified not only for the acoustic activity, but for the electromagnetic activity which is emitted during the catastrophic deformation of materials in the laboratory as well (Hadjicontis et al, 2004).…”