In this paper a method is presented for direct scaling of Pseudo Relative Velocity Spectra (PSV) in terms of: (1)Earthquake magnitude M and epicentral distance R; or (2)Modified Mercalli Intensity (MMI) at a site. These models also depend directly on the geologic site conditions and are presented for horizontal and for vertical ground motions. This scaling is realized by means of coefficient functions which are determined through regression analysis of computed PSV spectra from recorded accelerograms. One of the principal advantages of the proposed method is that the ambiguities associated with the scaling of the fixed shape spectra by means of peak amplitudes of ground motion are now completely eliminated. The 91 direct regressions of horizontal and vertical spectra, at 91 periods, smoothed over all periods, lead to more complete and reliable sampling of the frequency-dependent characteristics of strong ground motion than the correlations of peak amplitudes alone.