Abstract
Abstract. It has been suggested that fracture-induced MHz–kHz electromagnetic emissions (EME), which emerge from a few days up to a few hours before the main seismic shock occurrence permit a real-time monitoring of the damage process during the last stages of earthquake preparation, as it happens at the laboratory scale. Despite fairly abundant evidence, electromagnetic (EM) precursors have not been adequately accepted as credible physical phenomena. These negative views are enhanced by the fact that certain "puzzling features" are repetitively observed in candidate fracture-induced pre-seismic EME. More precisely, EM silence in all frequency bands appears before the main seismic shock occurrence, as well as during the aftershock period. Actually, the view that "acceptance of "precursive" EM signals without convincing co-seismic signals should not be expected" seems to be reasonable. In this work we focus on this point. We examine whether the aforementioned features of EM silence are really puzzling ones or, instead, reflect well-documented characteristic features of the fracture process, in terms of universal structural patterns of the fracture process, recent laboratory experiments, numerical and theoretical studies of fracture dynamics, critical phenomena, percolation theory, and micromechanics of granular materials. Our analysis shows that these features should not be considered puzzling.
Highlights
In recent years, the wind prevailing in the scientific community does not appear to be favorable for earthquake (EQ) prediction research, in particular for the research of short-term prediction (Uyeda et al, 2009)
Direction, we have shown that the populations of the EQs that precede a significant seismic event and occur around its epicenter, and the “fracto-EM EQs” that emerge during the fracture of the population of asperities follow the same statistics, namely the relative cumulative number of EQs/EM-EQs vs. magnitude, either in terms of the traditional Gutenberg–Richter law (Kapiris et al, 2004) or by means of a model of EQ dynamics that is based on first principles of non-extensive statistical mechanics (Papadimitriou et al, 2008; Minadakis et al, 2012a, b)
In this work we studied a paradox associated with a series of different EM seismic precursors ranging from direct current (DC) to MHz frequency bands, namely their observed silence before the main seismic shock occurrence
Summary
The wind prevailing in the scientific community does not appear to be favorable for earthquake (EQ) prediction research, in particular for the research of short-term prediction (Uyeda et al, 2009). The idea that the fracture-induced MHz–kHz EM fields should permit the monitoring of the gradual damage of stressed materials in the Earth’s crust, as happens in the laboratory experiments, in real time and step by step, seems to be justified: the aspect of self-affine nature of faulting and fracture is well documented. There may be legitimate reasons for the critical views concerning the reliability of EM precursors These negative views are supported by the fact that specific “puzzling features” are systematically observed in candidate pre-seismic EME.
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