Impact of near-fault earthquakes on North American design guidelines for nuclear structures

Ground motion records from recent earthquakes show that near-fault ground motions are different from far-field ground motions in that they often contain strong coherent dynamic long period pulses and permanent ground displacements. The objective of the current study is to assess the safety implications of near-fault earthquakes on nuclear power plant structures. Fifty-four fault normal near-fault records in the forward directivity were selected for this investigation. Spectral comparison of the selected earthquake records with the Canadian and US design spectra was conducted. From the investigation it was concluded that the current nuclear design spectra may need to be adjusted to better reflect the effect of near-fault earthquake ground motions.