Comparison of the 2‐D and Quasi‐3‐D Geoelectric Models of the Ukrainian Eastern Carpathians and Their Link to the Tectonic Structure

Abstract

We present results of a study of the electrical conductivity distribution beneath the Ukrainian Eastern Carpathians where the Carpathian arc turns to the southeast and reaches the maximum curvature further in the Romanian territory. We have used the magnetotelluric and magnetovariational data in the period range of 1–6,000 s collected by geoelectric groups from several countries during deep induction experiments, which covered the studied area by a number of field stations clustered along profiles crossing the Carpathian arc. In this work, we compare the 2‐D and quasi‐3‐D thin sheet inverse models, which allow us to constrain both the geometry and electrical properties of the anomalous conductivity structures beneath the Carpathians. Comparison of the inverse results with the Carpathians tectonics indicates that the Carpathian conductivity anomaly within the Polish and Slovak territory is located approximately between the Magura nappe front and the Pieniny Klippen Belt. In Ukraine, where the Magura nappe narrows and disappears, the anomaly reaches the front of the Outer Carpathians. The resulting quasi‐3‐D model of the conductivity structure beneath the Carpathians is compared with other geophysical and geological data within the region. The relation of the position of the conductors to the heat flow models and to location of the earthquakes sources indicates possible geological mechanisms, such as saline pore fluids, thin films of grain boundary graphite, or partial melting, connected with recent activation zones.

Geodynamics

“…Such behavior associated with fluids migration in faults zones has been described, for example, in [Unsworth and Bedrosian, 2004] and reported in tectonically active regions (e.g. [Srebrov et al, 2018;Kováčiková et al, 2016Kováčiková et al, , 2019. The aseismicity of the rest of the region may be due to the fact that the level exceeding the critical elastic stress (for rock strength) has not yet been reached.…”

“…In previous works of the authors, the geoelectric parameters of the earth's crust and upper mantle of Ukraine were estimated using 1D and 2D inversions of MT data [Gordienko et al, 2005;2012;Logvinov, 2015;Logvinov et al, 2017;Logvinov and Tarasov, 2019]. Based on magnetovariational data (MV, only magnetic components of MT field), the areal distribution of the integrated conductivity (conductance S) of the earth's crust of the Carpathians and adjacent part of the EEP was analyzed using quasi-3D inversion [Kováčiková et al, 2019]. As a result, the presence of numerous high conductivity / low resistivity structures ( r <100 ohmm) has been confirmed in the earth's crust of the VPP.…”