Geophysical processes and biosphere: article

Аnnotation: Our investigations in episcopal basilica in Varna town have revealed a number of seismic deformations in its walls: numerous shifts, tilts and rotations of the wall parts around vertical axis, as well as through-going joints cutting few stone blocks consecutively. There is revealed a cluster of (minimum) three seismic events occurred during one hundred years interval: beginning of V - beginning of VI centuries AD. Judging by kinematic indicators in the basilica constructions built of high quality stone blocks, a source of seismic motions located apparently NNE of basilica. Strong seismic oscillations which traces were revealed in later building constructions propagated apparently from SW. The seismic sources located along active faults localized north and south of Varna. Local seismic intensity of studied earthquakes was Il ≤ 9 according to MSK-64 Scale. The intensity of the seismic oscillations was increased by unfavorable ground conditions in basilica location. Obtained materials have to be considered at new seismic hazard assessment for Varna town and at creation of new map of seismic zoning of North-Eastern Bulgaria.