An Evolutionary Approach for the Synthesis of Spectrum Compatible and Site-Dependent Earthquake Accelerograms

This paper proposes a numerical procedure for the generation of sets of synthetic acceleration time-histories that are compatible with an assigned target design spectrum. The proposed formulation is able to take into account for both the energy distribution in time and the contemporary variability of the frequency content. In particular the discussed time-frequency approach is based on the possible decoupling of the distribution in time of the energy release from the changing frequency content. The decoupling of the two main sources of the non-stationary behavior observed in natural earthquake records is obtained by defining two different modulating functions one governing the intensity of signal and the other ruling the evolution of the frequency content. The proposed approach allows the recognition of strict relations between recorded accelerograms at a site and the underlying evolutionary model here proposed for the generation of spectrum compatible time histories.