  For earthquake-resistant design, engineering seismologists employ
time-history analysis for nonlinear simulations. The nonstationary stochastic
method previously developed by Pousse et al. (2006) has been updated. This
method has the advantage of being both simple, fast and taking into account the
basic concepts of seismology (Brune's source, realistic time envelope function,
nonstationarity and ground-motion variability). Time-domain simulations are
derived from the signal spectrogram and depend on few ground-motion parameters:
Arias intensity, significant relative duration and central frequency. These
indicators are obtained from empirical attenuation equations that relate them
to the magnitude of the event, the source-receiver distance, and the site
conditions. We improve the nonstationary stochastic method by using new
functional forms (new surface rock dataset, analysis of both intra-event and
inter-event residuals, consideration of the scaling relations and VS30), by
assessing the central frequency with S-transform and by better considering the
stress drop variability.
