The three-dimensional geoelectric model of earth crust and upper mantle of the Dobrudga region

2015;
: pp. 55 - 62
https://doi.org/10.23939/jgd2015.01.055
Received: April 16, 2015
1
Subbotin Institute of geophysics of National Academy of Sciences of Ukraine
2
Subbotin Institute of geophysics of National Academy of Sciences of Ukraine
3
Semenenko Institute of geochemistry, mineralogy and ore formation, NAS of Ukraine; Subbotin Institute of geophysics of NAS of Ukraine
4
Semenenko Institute of geochemistry, mineralogy and ore formation, NAS of Ukraine

Purpose. The purpose of researches is to build a three-dimensional geoelectric model of the crust and upper mantle and to answer some questions of the deep structure and geodynamics of the North Dobrudga and PeriDobrudga depression. Methodology. The methodology includes a detailed analysis of the deep structure of the region based on the results of 3D modeling of electromagnetic experimental data and to search for the interrelation between conductivity anomalies in the Earth’s crust and upper mantle and foci of seismic events. Results. Anomalies of high electric conductivity from the surface of the Earth crust to the upper mantle are identified. Stretched for hundreds of kilometers conductors are associated with deep conductive fractures of different fractures: Frunze, Saratsky, Bolgrad, Cahul-Izmail, Chadyrlungsk and others. A highly conductive layer is identified on the southern side of PeriDobrudga depression which lies at the depth corresponding to the lower crust and the top part of upper mantle. North side of PeriDobrudga depression is characterized by the distribution of electrical conductivity in the upper mantle which is the same as that of EEP, while presence of conductive structure at the depths of 110 to 160 km differs the southern slope from the northern one. Earthquake sources as well as anomalies of high electric conductivity are mainly correlated with active deep tectonic fractures and juncture zones of geological structures such as different age zones of Precambrian EEP and Cimmerian Scythian plate on the territory of PeriDobrudga depression and North Dobrudga. Originality. Three-dimensional deep geoelectric model built on experimental results of modern MTS and MVP data reflects inhomogeneous distribution of electric conductivity in the depth on the territory of PeriDobrudga depression and North Dobrudga. Practical significance. The results will make it possible to estimate more reliably the peculiarities of seismic hazard for the Dobrudga region of Ukraine and certain seismically active zones and structures.

1. Bugaenko I. V., Shymlanskaya L. A., Zaets L. N., Tsvetkova T. A. Three-dimensional P-velocity mo¬del of the mantle of the Black Sea and adjacent territories. Geophys. Journal, 2008, vol. 30, no. 5, рр. 145–160 (in Russian).
2. Burakhovich T. K., Kulik S. N., Logvinov I. M. Geo-electric model of the crust and upper mantle of PeriDobrudga deflection and North Dobrogea. Geophys. Journal, 1995, vol. 17, no. 4, рр. 81–87 (in Russian).
3. Burakhovich T. K. Kvazi-3D geoelectric model of the Carpathian region. Geophys. Journal, 2004, vol. 26, no. 4, рр. 63–74 (in Russian).
4. Burakhovich T. K., Kulik S. N., Kushnir A. N., Zai-tsev G.N., Ganiev A.Z., Sheremet E.M., Nikola-ev Y.I., Nikolaev I.Y. 3D geoelectric model of Dobrudga and PeriDobrudga depression. Trans-actions of UkrNDMІ NASU, 2011, vol. 9, no. 2, рр. 381–391 (in Russian).
5. Chekunov A. V. Veselov A. A., Gilkman A. I. Geo-logical structure and history of the development the Black Sea trough. Kyiv, "Nauk. Dumka" Publ., 1976, 156 p. (in Russian).
6. Drumea A. V., Ustinova T. I., Schukin J. K. Problems of tectonics and Seismology of Moldova. Kishinev, "Karty Modvii" Publ. 1964, 119 p. (in Russian).
7. Hain V. E. Tectonics of the continents and oceans. Moscow, "Scientific World" Publ. 2001, 586 p. (in Russian).
8. Ingerov A. I., Bugrimov L. P. et al. The results of MTZ on the site Kealia – Krivoy Rog – Kharkov. Lithosphere of Central and Eastern Europe. Geo-traverses ІV, VІ, VІІ. Kyiv, "Nauk. Dumka" Publ., 1988, рр. 145–150 (in Russian).
9. Kulik S. N. Lankis L. K., Lysenko E. S. The results of numerical modeling of deep geoelectric section in the region of the Eastern Carpathians and adjacent territories. Geophys. Journal, 1995, vol. 17, no. 4, рр. 81–87 (in Russian).
10. Kulik S. N. The northern branch of the Eurasian conductivity anomalies. Geophys. Journal, 2009, vol. 31, no. 4, рр. 168–180 (in Russian).
11. Kutas V. V., Omelchenko V. D., Ostroukhova O. A. Epicenters of earthquakes in the southwest Ukrai-ne. Geophys. Journal, 2005, vol. 27, no. 6, рр. 96–96 (in Russian).
12. Mackie R. L., Madden T. R., Wannamaker P. E. Three-dimensional magnetotelluric modeling using difference equations – theory and comparison to integral equation solutions. Geophysics, 1993, Vol. 58, pp. 215–226.
13. Mackie R. L., Smith J. T., Madden T. R. Three-dimen¬sional magnetotelluric modeling using dif-ference equations. The magnetotelluric example, Radio Science, 1994, Vol. 29, no. 4, pp. 923–935.
14. Nikonov A. A., Nikonova K. I. On the seismic hazard in Danube River delta according to the data of the historical earthquakes. Problems of engineering seismology, 1990, Vol. 31, pp. 127-134 (in Russian).
15. Pinna E., Soare A., Stanica D., Stanica M. Carpathian conductivity anomaly and its relation to deep structure of the substratum. Acta. Geod., Geoph. Et Mont. Hung., 1982, Vol. 27, no. 1, рр. 35–45.
16. Pustovitenko B. G., Kulchytsky V. E., Pustovitenko A. A. New maps of general seismic division into districts of the territory of Ukraine. Features of the model of long-term seismic hazard. Geophys. Journal, 2006, Vol. 28, no. 3, рр. 54–77 (in Russian).
17. Rokityansky I. I., Logvinov I. M., Rokityanskaya D. A. Black Sea branch of the Carpathian anomaly of electric conductivity. Geophys. Journal, 1979, no. 87, рр. 65–67 (in Russian).
18. Stănică M., Stănică D., Marin-Furnica C. The place-ment of the Trans-European Suture Zone on the Romanian territory by electromagnetic arguments. Earth Planet. Space, 1999, Vol. 51, рр. 1073–1078.
19. Tsvetkova T. A., Bugaenko I. V. Seismotomography of mantle beneath the East European platform : velocity mantle boundary. Geophys. Journal, 2012, vol. 34, no. 5. рр. 161–170 (in Russian).
20. Zhdanov M. S., Golubev N. G., Varentsov I. M., Abramova L. M., Shneer V. S., Berdichevsky M. N., Zhdanova O. N., Gordienko V. V., Bilins-ky A. I., Kulik S. N. 2D model fitting of a geomagnetic anomaly in the Soviet Carpathians. Annal. Geophys., 1986, Vol. 4B, no. 3, рр. 335–342.