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| Titel |
Evolving towards a critical point: A possible electromagnetic way in which the critical regime is reached as the rupture approaches |
| VerfasserIn |
P. G. Kapiris, K. A. Eftaxias, K. D. Nomikos, J. Polygiannakis, E. Dologlou, G. T. Balasis, N. G. Bogris, A. S. Peratzakis, V. E. Hadjicontis |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 10, no. 6 ; Nr. 10, no. 6, S.511-524 |
| Datensatznummer |
250008207
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| Publikation (Nr.) |
 copernicus.org/npg-10-511-2003.pdf |
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| Zusammenfassung |
| 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 radio-electromagnetic 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 electro-magnetic 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
electromagnetic critical behaviour of the failing system is? |
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