Anomalous geomagnetic fields of internal origin in Czechoslovakia

Praus, Oldřich; Pěčová, Jana

doi:10.1007/bf01628074

Cited by 10 publications

(5 citation statements)

References 6 publications

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“…Geomagnetic induction experiments in the studied region have been performed since 1973 (Jankowski et al, 1985;Červ et al, 1984, 1987Pěčová et al, 1976;Praus and Pěčová, 1991). The long-period (1000−6000 s) geomagnetic transfer functions and induction vectors were collected at 143 temporary sites arranged along profiles crossing the eastern margin of the Bohemian Massif, the transition zone and the West Carpathians (Fig.…”

Section: Experimental Datamentioning

confidence: 99%

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Modelling of the conductance distribution at the eastern margin of the European Hercynides

Kováčiková¹,

Červ²,

Praus³

2005

Stud Geophys Geod

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Magnetic variation data recorded at 143 sites in the period range of 1000−6000 seconds were used to model the conductance distribution in the eastern part of the Bohemian Massif (BM) and the West Carpathians (WCP). The region represents a contact zone of the Palaeozoic Hercynian and Tertiary Carpathian orogenic systems. Two anomalies in the distribution of the electrical conductivity were found. One with a simple two-dimensional feature is located approximately near the boundary of the Inner and Outer West Carpathians, but the other of a complicated three-dimensional character is at the eastern margin of the BM. We inverted the observed geomagnetic data for the conductance in a unimodal thin sheet embedded at a specific depth. The inversion algorithm minimises the parametric functional that sums the squared norm of the misfit and the stabilising functional, and employs conjugate gradient optimisation. To express the sharp tectonic boundaries, we employed a minimum gradient support functional, which is applied in areas with strong variations of the model parameters. The inversion results confirmed a quasi-linear character of the regional anomaly distinguishing the Carpathian plate and led to new insight into the anomaly over the eastern margin of the BM. According to the results of the modelling the anomaly is formed by several conductive belts intersecting the anomalous zone. These belts follow important faults, dividing the transition zone between the BM and the WCP into individual blocks.

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Section: Experimental Datamentioning

confidence: 99%

“…Measurements of magnetic variations in this area revealed two zones of anomalous induction that obviously mark the boundaries of the above-mentioned tectonic units: the West Carpathian anomaly (WCA) and the anomaly in the eastern part of the Bohemian Massif (BMA) (Jankowski et al, 1985;Praus and Pěčová, 1991) shown in Figs. 3 and 4.…”

Section: Introductionmentioning

confidence: 99%

Modelling of the conductance distribution at the eastern margin of the European Hercynides

Kováčiková¹,

Červ²,

Praus³

2005

Stud Geophys Geod

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“…According to previous modeling results, the CrCA is indicated clearly in all profiles and seems to be located between the Magura nappe and the PKB (Jankowski et al, 1977). The obtained 2D models were used as a priori information for a subsequent quasi-3-D modeling of the conductivity distribution, which aimed at fitting the vertical magnetic transfer functions W z,x and W z,y , (components of induction arrows) across the whole area including former Czechoslovakia, Poland, Hungary, and Ukraine (Adam et al, 1997;Jankowski et al, 1985;Praus & Pěčová, 1991) by the regional distribution of the integrated electrical conductivity (conductance) S. The quasi-3-D modeling and inversion was based on the thin sheet approximation of the crustal structures, where the anomalous source was replaced by a thin sheet with anomalous conductance S at a specified depth in the layered Earth. In the unimodal approach, the vertical currents' effect is neglected, and the horizontal equivalent currents within the thin sheet can be calculated using the Price equation.…”

Section: Quasi-3-d Inversion Resultsmentioning

confidence: 99%

“…The vertical and horizontal magnetic field components in the single‐site measurements are related by vertical geomagnetic transfer functions (again complex terms)

H_{z} = W_{zx} H_{x} + W_{zy} H_{y}

and expressed on maps by induction arrows C u = ReW zx + iReW zy and C v = ImW zx + iImW zy (Schmucker, ) pointing outside the conductive feature in Wiese () convention. Experimental induction arrows demonstrate clear reversals over the anomaly axis along the whole Carpathians arc from former Czechoslovakia through Poland and Ukraine to Romania (Jankowski et al, ; Logvinov & Tarasov, ; Pinna et al, ; Praus & Pěčová, ). In Figure a, the induction arrows over the Ukrainian Carpathians are shown for the period T = 1,600 s. The methodology of survey is described in Logvinov and Tarasov ().…”

Section: Experimental Data and Results Of Geoelectric Studiesmentioning

confidence: 99%

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

Kováčiková

Logvinov²,

Tarasov³

2019

Tectonics

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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.

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“…Induction response data at 150 field stations, that were published earlier (Praus and Pecova, 1991), covering the Bohemian Massif (BM), the Brunovistulicum (BV), and the West Carpathian region (WCP) have been re-analyzed (Pecova and Praus, 1996). Spatial distribution of both the in-phase and out-of-phase induction vectors, as well as contour maps of the individual elements of the transfer functions (TF) and contour maps of the anomalous vertical field, that were generated from the TFs by a hypothetical field with different polarizations, and systems of related internal anomalous currents (Kovacikova et al, 1997) prove the existence of two zones of anomalous induction at the eastern margin of the BM and near the boundary of the Carpathian plate.…”

Section: Introductionmentioning

confidence: 99%

Model of Electrical Conductivity Distribution across Central Europe

Červ¹,

Kováčiková²,

Pek³

et al. 1997

J. geomagn. geoelec

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This contribution is aimed at suggesting and analyzing a thin sheet model of the electrical conductivity structure beneath Central Europe that would fit the induction response data, specifically the in-phase induction vector distribution. In particular, attention is paid to fitting the reversals of the induction vectors that suggest the existence of elongated zones of high electrical conductivity distinguishing main structural units.

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Anomalous geomagnetic fields of internal origin in Czechoslovakia

Cited by 10 publications

References 6 publications

Modelling of the conductance distribution at the eastern margin of the European Hercynides

Modelling of the conductance distribution at the eastern margin of the European Hercynides

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

Model of Electrical Conductivity Distribution across Central Europe

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