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Some results of the investigation of geomagnetic field variation in the Urals and the Carpathians |
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| Authors: | Vsevolod A Shapiro Valentina G Kuznetsova |
| Institution: | Institute of Geophysics, Urals Scientific Centre, USSR Academy of Science, Sverdlovsk, USSR;Department of Mathematical Physics of the Institute of Mathematics, Ukrainian Academy of Science, Lvov, USSR |
| Abstract: | Summary. A precision magnetic survey for the investigation of current activity in the Earth's lithosphere has been carried out in the Urals and in the Carpathians. As a result of this research three types of time variation of the total field were discovered. These are: (1) The normal field variation reflecting the general pattern of secular variation. The difference of initial and repeat observation where only this type of variation operates, is rather small and usually does not exceed 0.2–0.3 nT. The field changes in such regions can be used only to evaluate the observation errors and to provide the regional pattern of secular variation. (2) The slow but localized'anomalous field'change from year to year corresponding, presumably, to anomalies of a tectonomagnetic nature. The normal pattern of the secular variation field here is disturbed by sources located in the upper part of the lithosphere. (3) Irregular time changes of the field with rather large amplitudes (up to 10–20 nT). Repeated observations of such anomalies show that the field changes significantly here even during one day. Both in the Urals and Carpathians these anomalies form extended elongated structures with widths up to 10–30 km. These anomalies usually coincide with those deep faults where the strongest recent crustal movements have been determined by means of geodetic observations. The analysis of the results of precision geomagnetic surveys in the Urals and in the Carpathians shows that geomagnetic investigations can be used for the exploration of tectonically active zones. |
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