The microseismic survey method was applied to the study of the geological structures in the region around the Mochovce nuclear power plant. The previous geological and geophysical investigations considered a contact between the Miocene volcanites and sediments as a neotectonic fault. The results of the microseismic investigations allow us to interpret the zone of a supposed neotectonic fault as a transgressive contact of the sediments and the volcanic rocks without a tectonic disruption.