ABSTRACT
All technological and industrial systems represent significant sources of risk. It is the reason for risk management with effort to provide a safe facility and its safe surroundings. There are many techniques used for the seismic hazard assessment and consequently for the seismic risk assessment. The paper compares the values of seismic hazard determined according to the map of maximum observed intensities, calculated by the extreme value, by the margin value theory (median, median + σ) and by the procedure used for seismic PSA. The example documents that the differences among the calculated values exceed the values of standard deviations, which supports the existence of vagueness (epistemistic uncertainties). The present reality naturally induces the question which value of determined ones is just the right one to be the value given in terms of references of object, the seismic safety of which we want to ensure.
