Relaxation creep model of impending earthquake

Abstract

The alternative view of the current status and perspective of seismic prediction studies is discussed. In the problem of ascertainment of the uncertainty relation Cognoscibility-Unpredictability of Earthquakes, priorities of works on short-term earthquake prediction are defined due to the advantage that the final stage of nucleation of earthquake is characterized by a substantial activation of the process while its strain rate increases by the orders of magnitude and considerably increased signal-to-noise ratio. Based on the creep phenomenon under stress relaxation conditions, a model is proposed to explain different images of precursors of impending tectonic earthquakes. The onset of tertiary creep appears to correspond to the onset of instability and inevitably fails unless it is unloaded. At this stage, the process acquires the self-regulating character and to the greatest extent the property of irreversibility, one of the important components of prediction reliability. Data in situ suggest a principal possibility to diagnose the process of preparation by ground measurements of strain-rate-dependent parameters, like electromagnetic emission, etc. Laboratory tests of the measurements of acoustic and electromagnetic emission in the rocks under constant strain in the condition of self-relaxed stress until the moment of fracture are discussed in context. It was obtained that electromagnetic emission precedes but does not accompany the phase of macrocrack development.

Current challenges for pre-earthquake electromagnetic emissions: shedding light from micro-scale plastic flow, granular packings, phase transitions and self-affinity notion of fracture process

“…(i) The launch of the preseismic MHz radiation systematically precedes the kHz one (Gokhberg et al, 1995;Matsumoto et al, 1998;Hayakawa Fujinawa, 1994;Hayakawa, 1999;Morgounov, 2001;Kapiris et al, 2004;Eftaxias et al, 2002, and references therein). This situation is also observed at the laboratory scale by means of AE and EME.…”

“…However, recent accumulated experimental evidence enhanced some older ones indicating that the aforementioned well accepted view was false; the recorded AE and EME, in general, are not two sides of the same coin. Indeed, simultaneous laboratory measurements of AE and EME reveal the existence of two categories of AE signals (Yamada et al, 1989;Mori et al, 1994;Morgounov, 2001;Mori et al, 2004aMori et al, , b, 2006Mori et al, , 2009Mori and Obata, 2008;Lacidogna et al 2010;Baddari and Frolov, 2010;Carpinteri et al, 2012) As it was mentioned, laboratory studies reveal that strong AE and EME are simultaneously observed during stress drops occurred close to peak stage in the load versus time diagram (Fukui et al, 2005;Lacidogna et al, 2011;Carpinteri et al, 2011;Carpinteri et al, 2012). At this stage new fresh surfaces, which are accompanied by the rupture of interatomic bonds and charge separation, are produced.…”

“…Thus the simultaneous emission of strong kHz AE and EME is reasonable. However, during the last phase of the post-peak stage, that is the softening branch in the load versus time diagram, which is not accompanied by significant production of new surfaces, no EME is detected, while, on the contrary, the most intense AE emerges (e.g., Morgounov, 2001;Baddari and Frolov, 2010;Carpinteri et al, 2012).…”

“…1. A common observation from all of the experiments designed to detect fracture induced EM precursors at the geophysical scale is that MHz-kHz signals are observed before EQs, but these signals are not observe at the time of EQs occurrence, namely, an EM silence systematically emerges before the time of the EQ occurrence (Gokhberg et al, 1995;Matsumoto et al, 1998;Hayakawa Fujinawa, 1994;Hayakawa, 1999;Morgounov, 2001;Eftaxias et al, 2002 and references therein;Eftaxias et al, 2012) . The following relevant argument is often raised by some scientists leading them to the conclusion that the observed kHz EM anomalies are not preseismic ones, despite the existence of any other strong multidisciplinary documentation supporting their validity (e.g., Park et al, 1993;Geller, 1997;Geller et al, 1997b;Johnston, 1997): If the recorded EM signals are emitted from microfracturing, why isn't any EM signal detected at the time of the EQ occurrence?…”

Unfolding the procedure of characterizing recorded ultra low frequency, kHZ and MHz electromagetic anomalies prior to the L'Aquila earthquake as pre-seismic ones – Part 1

“…The existence of finite-time-singularity in the anomalies strongly supports the hypothesis of presence of a positive feedback mechanism, which expresses a positive circular causality that acts as a growth-generating phenomenon and therefore drives unstable patterns (Telesca and Lasaponara, 2006). The appearance of the property of irreversibility in a probable precursor is one of the important components of predictive capability (Morgounov, 2001).…”