Holocenic Geological and Seismic Activity of the Fault System in Northeastern Bulgaria by the Complex of Geological-Geomorphological and Archeoseismological Methods

The structure of the fault system of northeastern Bulgaria and, in particular, of the Intramoesian fault, is examined in order to assess their current activity. The Intramoesian fault and its branch disjunctives have not been sufficiently studied from the geological-geomorphological and seismological points of view. The authors conduct a complex of geophysical investigations and obtain an idea of their deep structure. The system of these faults is a key element in solving the problem of assessing the seismic hazard of the region, since recent studies of this territory indicate the existence of traces of relatively young seismotectonic processes. There is also an opinion that the zone of the two Intramoesian faults disturbs the eastern part of the tectonic plate, which is subducted under the Carpathian fold system in the region of the Vrancea Mountains. The results of the field study of the southeastern Bulgarian part of these fault systems by a complex of geological-geomorphological, paleoseismological, and archeoseismological methods are presented. The zone of the Intramoesian fault is structurally segmented and the features of its intersection with the disjunctives of another structural orientation are revealed based on this. The data that determine the degree of its geological and seismic activity are discussed.