Seismic load assumptions in low seismic zones

A procedure for the determination of realistic site-specific load assumptions for nuclear power plants in low seismic zones is presented. A macroseismic site analysis yields i) a probabilistic definition of the site intensity of the design earthquake and ii) the ranges of magnitudes and focal distances which mainly contribute to this intensity. The subsoil conditions at the site are assigned to one of three classes: medium, alluvium or rock. Based on these criteria representative strong motion records are selected from an earthquake data bank containing primarily near-field registrations typical for European sites. The response spectra or Fourier spectra of the selected accelerograms and the duration of strong motion are evaluated statistically yielding site-specific specifications of frequency content and duration of ground motion serving as basis for aseismic design. (orig.)