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| Titel |
On the nature, scaling and spectral properties of pre-seismic ULF signals |
| VerfasserIn |
F. Vallianatos, A. Tzanis |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 3, no. 3/4 ; Nr. 3, no. 3/4, S.237-242 |
| Datensatznummer |
250000682
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| Publikation (Nr.) |
 copernicus.org/nhess-3-237-2003.pdf |
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| Zusammenfassung |
| Earlier work by the
authors (Vallianatos and Tzanis, 1999b), has proposed a model for the
propagation and scaling of electric earthquake precursors, according to
which the pre-seismic electric field emission is due to some time
dependent polarisation appearing in an ensemble of electrified crustal
volumes within the seismogenic source, which are distributed according to
a fractal power law. Herein, we extend this formulation to the analysis of
ULF magnetic precursors. We calculate the resulting transient magnetic
field, which turns out to be mainly vertical and observable only if the
seismogenic process generates a source with polarization rate
perpendicular to the vertical plane through the source and the receiver.
Furthermore, a scaling law between the vertical magnetic field and the
magnitude of the associated earthquake is provided. We also investigate
the spectral distribution law expected from such a set of emitters. To
this effect, we assume that the evolution of the precursory polarisation
process is quasi-incoherent over the exited ensemble, i.e. there is no
unique relaxation time, but rather a spectrum of these with energy
dependence expressed by an Arrhenius law with uniformly distributed
energies. We show that the macroscopic ULF field resulting from the
superposition of such an ensemble of sources has a power density spectrum
distributed proportionally to 1/f . The above theoretical
prediction appears to be consistent with independent observations by other
investigators. |
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