Detection of electromagnetic earthquake precursory signals in Greece

Eftaxias, K.; Kopanas, J.; Bogris, N.; Kapiris, P.; Antonopoulos, G.; Varotsos, P.

doi:10.2183/pjab.76.45

Cited by 34 publications

(51 citation statements)

References 2 publications

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“…During the period 1995-1999 two additional destructive Earthquake occurred in continental Greece: on 15 June 1995 the Egio-Eratini (Ms = 6.5) and on 7 September 1999 Athens Earthquake (Ms = 5.9). These Earthquake were preceding by a sequence of EM anomalies (Eftaxias et al, 2000). One can recognize that the recorded sequence of ULF, VLF and VHF electromagnetic emissions before the KozaniGrevena Earthquake was observed during quiet magnetic conditions.…”

Section: Geomagnetic Activity During Precursory Em Emissionsmentioning

confidence: 77%

“…Hence, in previous papers, we have shown that the evolutions of the sequence of the observed radio-emissions reveals similarities to that observed in laboratory acoustic and electromagnetic emissions during the last stages of failure preparation process in rocks . (ii) We have also shown that features of these precursors are possibly correlated with the corresponding fault model and with the degree of heterogeneity within the focal area (Eftaxias et al, 2000(Eftaxias et al, , 2001a. (iii) The VHF emission has a rather long duration, i.e.…”

Section: Introductionmentioning

confidence: 74%

“…A key parameter is the degree of disorder (Sornette, 2000). The VLF-anomalies for the three EQs in KozaniGrevena, Egion-Eratini and Athens differ in their leadtime: as the structure in the pre-focal area becomes less heterogeneous, the lead-time becomes smaller (Eftaxias et al, 2000(Eftaxias et al, , 2001b. Gershenzon et al (1989) have proposed a model for the micro-fracture of granular media consisting of rigid grains and interstices filled with a brittle elastic material.…”

Section: Discussionmentioning

confidence: 99%

“…Our main tool is the monitoring of micro-fractures that occurs before the final breakup, by recording their radio-electromagnetic emissions during the last tens of hours prior to the main shock Vallianatos and Nomikos, 1998;Eftaxias et al, 2000Eftaxias et al, , 2001aEftaxias et al, , 2002a. The observed precursory EM fluctuations might represent EM signatures of the energy rearrangements that occur as the external field drives the heterogeneous system of the pre-focal area from one meta-stable local free-energy minimum to another.…”

Section: Introductionmentioning

confidence: 99%

“…These bursts ceased approximately one hour before the Earthquake occurrence; (ii) very strong multi-peaked electromagnetic signals with sharp onsets and ends at 3 kHz and 10 kHz, lasting about half hour, emerged approximately one and half hour before the Earthquake (Fig. 1b) (Eftaxias et al, 2000); (iii) if someone follows the diurnal background pattern of the DC-ULF recordings finds the existence of a minimum around mid-day (Fig. 1c).…”

Section: Introductionmentioning

confidence: 99%

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Evolving towards a critical point: A possible electromagnetic way in which the critical regime is reached as the rupture approaches

Kapiris

Eftaxias

Νομικός

et al. 2003

Nonlin. Processes Geophys.

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Abstract. In analogy to the study of critical phase transitions in statistical physics, it has been argued recently that the fracture of heterogeneous materials could be viewed as a critical phenomenon, either at laboratory or at geophysical scales. If the picture of the development of the fracture is correct one may guess that the precursors may reveal the critical approach of the main-shock. When a heterogeneous material is stretched, its evolution towards breaking is characterized by the appearance of microcracks before the final break-up. Microcracks produce both acoustic and electromagnetic (EM) emission in the frequency range from VLF to VHF. The microcracks and the associated acoustic and EM activities constitute the so-called precursors of general fracture. These precursors are detectable not only at laboratory but also at geophysical scales. VLF and VHF acoustic and EM emissions have been reported resulting from volcanic and seismic activities in various geologically distinct regions of the world. In the present work we attempt to establish the hypothesis that the evolution of the Earth's crust towards the critical point takes place not only in a mechanical but also in an electromagnetic sense. In other words, we focus on the possible electromagnetic criticality, which is reached while the catastrophic rupture in the Earth's crust approaches. Our main tool is the monitoring of micro-fractures that occur before the final breakup, by recording their radioelectromagnetic emissions. We show that the spectral power law analysis of the electromagnetic precursors reveals distinguishing signatures of underlying critical dynamics, such as: (i) the emergence of memory effects; (ii) the decrease with time of the anti-persistence behaviour; (iii) the presence of persistence properties in the tail of the sequence of the precursors; and (iv) the acceleration of the precursory electromagnetic energy release. Moreover, the statistical analysis of the amplitudes of the electromagnetic fluctuations reveals the breaking of the symmetry as the theory predicts. Finally, we try to answer the question: how universal the observed Correspondence to: K. A. Eftaxias (ceftax@phys.uoa.gr) electromagnetic critical behaviour of the failing system is?

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Section: Geomagnetic Activity During Precursory Em Emissionsmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 74%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Evolving towards a critical point: A possible electromagnetic way in which the critical regime is reached as the rupture approaches

Kapiris

Eftaxias

Νομικός

et al. 2003

Nonlin. Processes Geophys.

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Features of the Electric Field HF Wave of the Sunsynchronous Orbit in the Solar Minimum Year

Yang

et al. 2011

Chinese J of Geophysics

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Using the electric field High Frequency (HF) waves recorded by the Instrument Champ Electrique (ICE) onboard the DEMETER spacecraft in a solar low year, the spatial features of the waves from 10 kHz to 3.33 MHz are studied. During the quiet time of the geomagnetics, the higher the HF wave, the bigger the power spectrum intensity when the frequency lies between 2.08 MHz and 3.33 MHz. At the same time, the power spectrum intensity is almost uniform at different longitudes and latitudes. The difference of the power spectrum intensity between different longitudes and latitudes on the dayside is less than that on the nightside. The seasonal changes of the HF power spectrum intensity show that there are peaks at the dayside low latitudes in the frequency bands of 1.25 MHz and 1.66 MHz. During the quiet time, the discrepancy of the power spectrum intensities between different longitudes and latitudes obviously occurs at the frequency bands of 0.42 MHz and 1.66 MHz especially at high latitudea of the northern hemisphere on the dayside. During the geomagnetic activity, the HF response mainly appears at the low frequency band especially in high-latitude areas. In the equator and regions close to the low latitudes (latitude is between ±40 • ), the geomagnetic response of the HF is weak while that on the nightside in the magnetotail direction becomes strong especially during storms. Both at the northern and southern high latitudes during the storms on the nightside, the biggest power spectrum intensity is ten times that during the quiet. The biggest power spectrum intensity on the dayside at high latitudes of the southern hemisphere during the substorm and the period of the high latitude magnetic perturbation are ten times that during the quiet time. Considering that the perturbation coming from the space has an effect on high-latitude areas during the substorm and the periods of the high-latitude magnetic perturbation, the enhancement of the HF power spectrum intensity may origin from the spatial process. In view of that the data used in this study were collected in the solar minimum year and most of the storms were very weak with the strongest storm belonging to the moderate storm, the enhancements of the HF power spectrum intensity during the strong, severe even the great storms may be more obvious. If there is anomalous accretion in local areas during the quiet time especially when there is no storm, the abnormal phenomena are likely the ionospheric seismic-response to the dynamic processes of the internal earth such as earthquake preparation.

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Studies on different geophysical and extra-terrestrial events within the Earth-ionosphere cavity in terms of ULF/ELF/VLF radio waves

Sanfui

Haldar

Biswas

2016

Astrophys Space Sci

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Detection of electromagnetic earthquake precursory signals in Greece

Cited by 34 publications

References 2 publications

Evolving towards a critical point: A possible electromagnetic way in which the critical regime is reached as the rupture approaches

Evolving towards a critical point: A possible electromagnetic way in which the critical regime is reached as the rupture approaches

Features of the Electric Field HF Wave of the Sunsynchronous Orbit in the Solar Minimum Year

Studies on different geophysical and extra-terrestrial events within the Earth-ionosphere cavity in terms of ULF/ELF/VLF radio waves

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