Geophysical Journal | 2013 volume 35 1

Possible nature of seismic activity of Cisdobrogea sag and North Dobrogea depths

© V.I. Starostenko, T.K. Burakhovich, A.N. Kushnir, O.V. Legostayeva, T.A. Tsvetkova, E.M. Sheremet, L.A. Shumlyanskiy

PeriDobruzha depression and its surrounding belong to border zone of the mantle under the EEP, distinguished by the changes of zero isoline of velocity discrepancies with the depth within the limits of the upper mantle and its transition zone according to the data of 3D P-velocity model. The system of inclined layers corresponds to mantle border zone. Special features of mantle velocity structure under PeriDobruzha depression and its surrounding made possible to partition mantle prerequisites of seismicity of the area under consideration related to manifestation of mantle plume in the lower and medium mantle. Three-dimensional deep geo-electric model constructed according to the results of modern studies by MTS and MVP methods reflects heterogeneous distribution of present electric resistance in the depth of the region. Extended for hundreds of kilometers conductors are confined to deep conducting faults of different rank and their intersections. High-conductivity layer of complicated configuration is distinguished at the southern flank of the PeriDobruzha depression and occurs at the depths corresponding to lower crust and upper parts of the upper mantle. The source of the earthquakes as well as the anomalies of high electro-conductivity are mainly corresponding to occurrence of active deep tectonic faults and connection zones of geological structures of different ages. Within the interval of 28-30 eastern longitude - 45-46 northern latitude spatial disposition of electric conductivity anomalies comply with the area of manifestation of deep mantle fluids corresponding to mantle plume.

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