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VRANCEA SEISMIC ZONE - A NEW GEOPHYSICAL MODEL BASED ON WRENCH TECTONICS, VOLCANISM AND REGIONAL GEODYNAMICS
Abstract and Figures
The study dedicated to the Vrancea seismic zone is based on the interpretation of relevant geophysical data for regional, crustal and lithospheric geological structures: gravity, magnetics, refraction seismics, heat flow, and especially seismic tomography. New tectonic interpretations are offered at various scales, starting with the tectonic vortex determined by the three subduction zones in the Mediterranean Sea, Adriatic Sea and the East Carpathians, continuing with the wrench tectonics system developed between the Adriatic Sea and the Dniester river, and ending with the presence of the Romanian Trough, continuation of the Polish Trough along the western margin of the East European Platform. Reinterpretation of regional geophysical data, in the context of the newly proposed wrench tectonics system, and the tectonic events determined by horizontal displacement of large geological structures along the transcurrent faults, suggested that there is no need of another platform, such as the Scythian Platform, between the East European Platform and the Tisza-Dacia tectonic block, or of the Wallachian tectonic phase, postulated as being active during the Quaternary. Volcanism in Vrancea seismic zone is probably the most unexpected topic in an area long time considered to be devoid of magmatic processes-subduction related andesitic eruptions, followed by the intrusion of a large dioritic batholith, being interpreted on aeromagnetic, refraction seismics, seismic tomography and heat flow data, as well as on geological indirect evidences. The Vrancea zone high seismicity is interpreted to be associated at crustal levels with active normal faulting within the graben-like structure, in an extensional regime determined by the south-eastward regional drag, and to the strike-slip movements of the wrench tectonics southern transcurrent fault at lithospheric depths, in a transtensional regime.
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