Earth mantle conductivity beneath the Ukrainian territory

Abstract

Magnetovariation methods, which are applicable to study the mantle conductivity, require long lasting registration of natural magnetic field variations. Such data usually can be recorded in stationary conditions on geomagnetic observatories. The magnetotelluric and magnetovariation measurements have been carried out at seven semi-permanent sites on Ukrainian territory for approximately 10–15 years by the Ukrainian State Geological Research Institute as well as the S.I. Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine for monitoring the effects and phenomena related to electromagnetic field. Since the quality of records was acceptable, we used these data to study the Earth’s mantle conductivity peculiarities to obtain the information on sites remote from geomagnetic observatories. The Z-H method was applied to collected data to estimate the magnetovariaton transfer functions, which were concatenated with magnetotelluric ones and further inverted by the 1D OCCAM algorithm to obtain the geoelectrical cross sections for the measuring sites. To extend the region under study and to obtain more reliable results, similar data from three Ukrainian geomagnetic observatories in Kyiv, Lviv and Odessa were included in this study. Obtained conductivity models were related to the known geological structure in the upper and middle mantle beneath the Ukrainian territory.