Spectrum Compatible Earthquake Ground Motions by Morlet Wavelet

Time history analysis of structures for seismic loads requires a set of simulated design ground motions for this application. Spectral matching is the process of adjusting an actual earthquake accelerogram to match a target design spectrum. This procedure is very favorable for the development of design ground motions due to the evolution of worldwide network of seismic monitoring stations and hence the availability of many actual earthquake ground motion databases that reflect variability of important seismological parameters such as magnitude, distance, and rupture directivity. A time-domain spectral matching procedure is presented in this paper, wherein a recorded accelerogram is decomposed into its wavelet components at different frequencies through a continuous wavelet transform algorithm using a mother wavelet, and scaled iteratively such that the resultant time history is compatible with the target spectrum. It is shown that the Morlet wavelet can be used successfully to represent the mother wavelet for spectral matching. The procedure is illustrated by scaling a number of earthquake records to match the ASCE-7 Standard design spectrum at different seismic zones.