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THE INVESTIGATION OF AMPLITUDE-PHASE CHARACTERISTICS OF FICTITIOUS MAGNETIC CURRENTS, EXCITED BY THE CONTROLLED SOURCE OF ELECTROMAGNETIC FIELDS IN THREE-DIMENSIONAL INHOMOGENEOUS MEDIA, BASED ON THE RESULTS OF EXPERIMENTAL STUDIES BY RADIOGRAPHIC METHODтезисы доклада
- Автор: Lubchich V.A.
- Сборник: Abstracts of the 42st Annual Seminar on Physics of auroral phenomena
- Тезисы
- Год издания: 2019
- Первая страница: 22
- Последняя страница: 23
- Аннотация: The application of the radiographic method allows to effectively visualize the location of anomalous areas with high electrical conductivity, which can be associated with local ore bodies, by using areal surface observations of magnetic components of the harmonic electromagnetic field from the controlled source. The visualization of distribution of heterogeneities in the earth's crust by using the radioholographic method can be considered as a special case of the inverse scattering problem. During measurements of electromagnetic fields at observation points the superposition of two fields is recorded. One is the primary field from the controlled source, which, in holographic terms, can be treated as a reference wave. The other is secondary anomalous field caused by geoelectric heterogeneities in the earth's crust, which can be referred to as object waves. There is the integral equation that relates the holographic reconstruction of the magnetic field with unknown distribution of the density of fictitious magnetic currents jm, which are sources of anomalous fields. The system of linear equations with respect to unknown values jm at grid nodes is obtained after grid approximation of the integral equation. The definition of these values is the solution of the inverse scattering problem. In 2017-18 field experimental works were conducted by using the two-frequency radioholographic method for localization of ore zones in the earth's crust within the Monchegorsk and Pechenga ore regions of the Kola Peninsula. In the case of inductive excitation of electromagnetic fields in the earth's crust, when the horizontal ungrounded loop is used as the emitting antenna of controlled source, the induced eddy currents are predominantly subhorizontal. Due to this, the vertical component of the fictitious magnetic current density jmz is the most informative. According to the results of experimental studies, it was found that anomalous areas with high electrical conductivity corresponding to the location of ore zones were distinguished both by the maxima of amplitudes of the vertical component of the magnetic current density jmz, and by sharp jumps of phases, up to 180. It was also noted that anomalous zones with increased values of amplitudes of horizontal components of magnetic current density jmr have near-surface character. Due to this, it can be assumed that such anomalous zones are caused by tectonic faults, which are extremely widespread in ore regions of the Kola Peninsula. However, phase characteristics of horizontal components of the magnetic current density are more sensitive to deep anomalies of the electrical conductivity of the earth's crust. Sharp jumps of phases, up to 180, are observed at about the same depth as for the vertical component of the magnetic current density. Thus, the complex analysis of amplitude-phase characteristics of various components of the function of sources of anomalous electromagnetic fields jm allows to determine the most complete picture of the distribution of geoelectric heterogeneities in the earth's crust and to select those anomalous areas that are promising for the detection of local ore bodies. The study is executed at financial support of RFBR and the government of the Murmansk region (project No. 17-45-510956).
- Добавил в систему: Любчич Владимир Алексеевич