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| Titel |
Pre-earthquake signals – Part II: Flow of battery currents in the crust |
| 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.543-548 |
| Datensatznummer |
250004728
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| Publikation (Nr.) |
 copernicus.org/nhess-7-543-2007.pdf |
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| Zusammenfassung |
| When rocks are subjected to stress, dormant electronic charge carriers are
activated. They turn the stressed rock volume into a battery, from where
currents can flow out. The charge carriers are electrons and defect
electrons, also known as positive holes or pholes for short. The boundary
between stressed and unstressed rock acts as a potential barrier that lets
pholes pass but blocks electrons. One can distinguish two situations in the
Earth's crust: (i) only pholes spread out of a stressed rock volume into the
surrounding unstressed rocks. This is expected to lead to a positive surface
charge over a wide area around the future epicenter, to perturbations in the
ionosphere, to stimulated infrared emission from the ground, to ionization
of the near-ground air, to cloud formation and to other phenomena that have
been reported to precede major earthquakes. (ii) both pholes and electrons
flow out of the stressed rock volume along different paths, sideward into
the relatively cool upper layers of the crust and downward into the hot
lower crust. This situation, which is likely to be realized late in the
earthquake preparation process, is necessary for the battery circuit to
close and for transient electric currents to flow. If burst-like, these
currents should lead to the emission of low frequency electromagnetic
radiation. Understanding how electronic charge carriers are stress-activated
in rocks, how they spread or flow probably holds the key to deciphering a wide
range of pre-earthquake signals. It opens the door to a global earthquake
early warning system, provided resources are pooled through a concerted and
constructive community effort, including seismologists, with international
participation. |
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