A new methodology to determine elastic displacement spectra in the near-fault region

The evaluation of the displacement demand especially at small distances from the causative fault, in the so-called near-source region, is a subject of particular interest for earthquake engineering design, in the light of the growing application of the displacement-based design philosophy. This study presents a new methodology to determine the elastic displacement spectra using a sample of near-fault records from small-to-moderate magnitude earthquakes, typical of the seismic activity in Europe. The displacement spectrum is developed using near-fault attenuation relationships available in literature for peak ground velocity that is less sensitive in the procedures applied to correct the accelerograms. Also, the distance from the causative fault and the type of directivity are taken into consideration. The prevailing period corresponds to the maxima of the displacement spectra for zero damping and is used to normalize the spectra, leading to significant decrease of the statistical dispersion. The average bi-normalized spectrum, in terms of the peak ground displacement dg,max and the dominant period Td-p, appears to be slightly affected by the soil category and earthquake magnitude. A correlation between the damping correction factor η and the normalized period T/Td-p is detected and the applicability of several provisions of the current version of Eurocode 8 is examined, including characteristic periods and spectral amplitudes.

► Elastic displacement spectrum for near-fault records is assessed. ► Dominant period of motion is evaluated based on displacement spectrum. ► TD and TE periods of EC 8 spectrum are determined based on the dominant period. ► Bi-normalized spectrum appears to be unaffected by soil category and magnitude. ► Damping correction factors are proposed for near-fault ground motion.