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| Titel |
Pre-earthquake signals – Part I: Deviatoric stresses turn rocks into a source of electric currents |
| VerfasserIn |
F. T. Freund |
| 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 ; 7, no. 5 ; Nr. 7, no. 5 (2007-09-13), S.535-541 |
| Datensatznummer |
250004727
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| Publikation (Nr.) |
 copernicus.org/nhess-7-535-2007.pdf |
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| Zusammenfassung |
| Earthquakes are feared because they often strike so suddenly. Yet, there are
innumerable reports of pre-earthquake signals. Widespread disagreement
exists in the geoscience community how these signals can be generated in the
Earth's crust and whether they are early warning signs, related to the
build-up of tectonic stresses before major seismic events. Progress in
understanding and eventually using these signals has been slow because the
underlying physical process or processes are basically not understood. This
has changed with the discovery that, when igneous or high-grade metamorphic
rocks are subjected to deviatoric stress, dormant electronic charge carriers
are activated: electrons and defect electrons. The activation increases the
number density of mobile charge carriers in the rocks and, hence, their
electric conductivity. The defect electrons are associated with the oxygen
anion sublattice and are known as positive holes or pholes for short. The
boundary between stressed and unstressed rock acts a potential barrier that
lets pholes pass but blocks electrons. Therefore, like electrons and ions in
an electrochemical battery, the stress-activated electrons and pholes in the
"rock battery" have to flow out in different directions. When the circuit
is closed, the battery currents can flow. The discovery of such
stress-activated currents in crustal rocks has far-reaching implications for
understanding pre-earthquake signals. |
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