Frictional discharge at fault asperities: Origin of fractal seismo-electromagnetic radiation

Abstract. Many aspects of earthquake generation still escape our full understanding. Observations of electromagnetic emissions preceding significant earthquakes provide one of the few cases of premonitory events that are possibly related to a subsequent earthquake. Understanding the factors that control electromagnetic precursors generation seems to be important for determining how significant earthquakes nucleate. Here we report the results of a comprehensive study of the appearance of individual patterns in candidate electromagnetic precursors possibly indicating the breaking of backbone of large and strong asperities that sustain the activated fault. The search of precursory patterns is mainly based on well documented scaling properties of fault surface topology. More precisely, we argue that the candidate electromagnetic precursors might be originated during the slipping of two rough and rigid fractional-Brownian-motion-type profiles one over the other, with a roughness which is consistent with field and laboratory studies. The results also imply that the activation of a single earthquake (fault) is a reduced selfaffine image of the whole regional seismicity and a magnified self-affine image of the laboratory seismicity.

Section: Discussionmentioning

confidence: 99%

Evidence of fractional-Brownian-motion-type asperity model for earthquake generation in candidate pre-seismic electromagnetic emissions

Eftaxias

Contoyiannis

Balasis

et al. 2008

“…It was found that an increase of Young modulus, and index of brittleness and strength enhances the AE or EME amplitude (Hudson et al, 1972;Gol'd et al, 1975;Nitsan, 1977;Khatiashvili, 1984;Carpinteri, 1986Carpinteri, , 1989Carpinteri, , 1990Carpinteri, , 1994Frid et al, 1999Frid et al, , 2000Rabinovitch et al, 2002;Fukui et al, 2005). On the other hand, accumulated experimental and theoretical evidence indicates that the elastic modulus significantly decreases as damage increases, nearing zero as the global fracture approaches (Lockner and Madden 1991;Guéguen et al, 1997;Lin et al, 2004;Shen and Li, 2004;Amitrano and Helmstetter, 2006;Chen, 2012;Chelidze et al, 1988Chelidze et al, , 1990.…”

Section: On the Sensitivity Of The Fracture-induced Em Anomaly To Elamentioning

confidence: 99%

“…2.1.2). Muto et al (2007) conducted a friction laboratory experiment simulating the motion of an asperity on a fault plane, and observed photon emissions due to electric discharges by dielectric breakdown of ambient gases from friction contact between rock minerals. Those authors conclude that the frictional discharge occurring at asperities on the fault plane can be one of the origins of fractal EM radiation observed prior to EQs.…”

Section: Focus On the First Phasementioning

confidence: 99%

“…It was suggested in the earlier literature that "the mechanism of EQs is apparently some sort of laboratory fracture process" (Mogi, 1962a(Mogi, , b, 1968(Mogi, , 1985Ohnaka, 1983;Ohnaka and Mogi, 1982;Scholz, 1968Scholz, , 1990Scholz et al, 1973;Sobolev, 1995;Ponomarev et al, 1997;Ohnaka and Shen, 1999;Sobolev and Ponomarev, 2003;Muto et al, 2007;Kuksenko et al, 1996Kuksenko et al, , 2005Kuksenko et al, , 2007Kuksenko et al, , 2009Lei and Satoh, 2007). Recently, the aspect of self-affine nature of faulting and fracture is widely documented from analyses of data from both field observations and laboratory experiments in the spatial, temporal, and energy domains (Mandelbrot, 1982;Mandelbrot et al, 1984;Zavyalov and Sobolev, 1988;Gabrielov et al, 1999;Kuksenko et al, 2007;Davidsen and Schuster, 2002;Lockner et al, 1992;Diodati et al, 1991;Kapiris et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the puzzling feature of the silence of precursory electromagnetic emissions

Eftaxias

Potirakis

Chélidzé

2013

Abstract. It has been suggested that fracture-induced MHzkHz 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 fractureinduced 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.

“…Hazards Earth Syst. Sci., 10, [275][276][277][278][279][280][281][282][283][284][285][286][287][288][289][290][291][292][293][294]2010 www.nat-hazards-earth-syst-sci.net/10/275/2010/ scale (Hayakawa and Fujinawa, 1994;Hayakawa, 1999;Hayakawa et al, 1999;Gershenzon and Bambakidis, 2001;Hayakawa and Molchanov, 2002;Bahat et al, 2005;Eftaxias et al, 2007a;Muto et al, 2007;Hadjicontis et al, 2007). Studies on the small (laboratory) scale reveal that the MHz EM radiation appears earlier than the kHz one, while the kHz EM emission is launched from 97% up to 100% of the corresponding failure strength (Eftaxias et al, 2002 and references therein).…”

Section: Figmentioning

confidence: 99%

Unfolding the procedure of characterizing recorded ultra low frequency, kHZ and MHz electromagnetic anomalies prior to the L'Aquila earthquake as pre-seismic ones - Part 2

Eftaxias¹,

Athanasopoulou²,

Balasis³

et al. 2010

147

Abstract. Ultra low frequency-ULF (1 Hz or lower), kHz and MHz electromagnetic (EM) anomalies were recorded prior to the L'Aquila catastrophic earthquake (EQ) that occurred on 6 April 2009. The detected anomalies followed this temporal scheme. The question effortlessly arises as to whether the observed anomalies before the L'Aquila EQ were seismogenic or not. The main goal of this work is to provide some insight into this issue. More precisely, the main aims of this contribution are threefold: How can we recognize an EM observation as pre-seismic one? We aim, through a multidisciplinary analysis to provide some elements of a definition. How can we link an individual EM anomaly with a distinctive stage of the EQ preparation process? The present analysis is consistent with the hypothesis that the kHz EM anomalies were associated with the fracture of asperities that were distributed along the L'Aquila fault sustaining the system, while the MHz EM anomalies could be triggered by fractures in the highly disordered system that surrounded the backbone of asperities of the activated fault. How can we identify precursory symptoms in an individual EM precursor that indicate that the occurrence of the EQ is unavoidable? We clearly state that the detection of a MHz EM precursor does not mean that the occurrence of EQ is unavoidable; the Correspondence to: K. Eftaxias (ceftax@phys.uoa.gr) abrupt emergence of kHz EM emissions indicate the fracture of asperities. The observed ULF EM anomaly supports the hypothesis of a relationship between processes produced by increasing tectonic stresses in the Earth's crust and attendant EM interactions between the crust and ionosphere. We emphasize that we attempt to specify not only whether or not a single EM anomaly is pre-seismic in itself, but mainly whether a combination of emergent ULF, MHz and kHz EM anomalies could be characterized as pre-earthquake.