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Pre-earthquake ULF electromagnetic perturbations as a result of inductive seismomagnetic phenomena during microfracturingстатья
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 23 декабря 2020 г.
- Авторы: Surkov V.V., Molchanov O.A., Hayakawa M.
- Журнал: Journal of Atmospheric and Solar-Terrestrial Physics
- Том: 65
- Год издания: 2003
- Издательство: Pergamon Press Ltd.
- Местоположение издательства: United Kingdom
- Первая страница: 31
- Последняя страница: 46
- Аннотация: This paper proposes a generation mechanism of ULF electromagnetic noise observed several hours before some strong earthquakes. It is assumed that this effect results from the energization of crack formation and fracture process in a focal zone before the main shock. Electromagnetic noise is considered as a by-product of the summation of electromagnetic micro-fields appearing in the conductive medium ahead of acoustic micro-waves radiated by an ensemble of tensile cracks. These micro-fields and currents are generated due to the movement of conductive medium in the geomagnetic field. The electromagnetic perturbations depend on the direction diagram of radiation and the attenuation of acoustic waves emitted by opening cracks. We investigate two different zones and regimes of ULF magnetic field propagation. In the near zone we expect the prevailing diffusion regime, where the sign of components of electromagnetic fields is found to be the same for all the cracks independent of their space orientation. A similar coherent effect takes place at the far or acoustic zone. These surprising effects occur, because the effective magnetic moments of current systems generated by the cracks are always directed opposite to the vector of geomagnetic field; i.e. these moments are strongly paralleled. It was established that the coherent amplification of ULF signals generated by the cracks could appear if only their size exceeds several critical values. Such an effect might appear at the background of low seismic activity because the acoustic emission of cracks is incoherent. The averaging of the fields over the ensemble of opening cracks allowed us to relate the parameters of electromagnetic noise to porosity, volumetric strain, dilatational coefficient and average size of macro-cracks at the earthquake hypocenter. Our theory predicts magnetic and electric perturbations to be of the order of 1–10 nT and 1–10 microVolts/m, respectively, at the distance 10–50 km from the epicenter. These values are very close to those observed prior to the occurrence of earthquakes at Loma Prieta and Spitak.
- Добавил в систему: Сурков Вадим Вадимович