Generation of artificial earthquakes via the wavelet transform

A wavelet-based procedure is presented to generate an accelerogram whose response spectrum is compatible with a target spectrum. The acceleration time history of a recorded ground motion is decomposed into a number of component time histories. Next, each of the time histories is appropriately scaled so that its response spectrum matches a specified design spectrum at selected periods. The modified components are used to reconstruct an updated accelerogram, its spectrum is compared with the target spectrum and the process is repeated until a reasonable match is obtained. To achieve this goal, a new wavelet, based on the impulse response function of an underdamped oscillator is proposed. The proposed procedure is illustrated by modifying five recorded accelerograms with different characteristics so that their spectra match a seismic design spectrum prescribed in the 1997 Uniform Building Code for a seismic zone 3 and soil type SB (rock).