A wavelet-based parametric characterization of temporal features of earthquake accelerograms

Simulation of aftershock accelerograms is crucial to ascertaining structural safety against the additional cumulative damage during the aftershocks that would follow an anticipated main shock. Besides being consistent with a specified response spectrum, such an accelerogram should incorporate realistic temporal features. This paper considers a wavelet-based description of the time–frequency characteristics of a class of earthquake accelerograms and proposes three-parameter models for the modulation of wavelet coefficient envelopes of different frequency bands. Estimation of the modulation parameters is attempted through simple scaling models using easily available seismological and site parameters and with the help of the data of 1999 Chi-Chi earthquake and its aftershocks. Sensitivity of the simulated motions to the uncertainty in the estimation of modulation parameters is also studied. Further, it is shown that the simulated ground motions show expected variations in their temporal characteristics with regard to variations in the governing seismological and site parameters.