- See Section 2.71.
- Ground-motion model is:
- Response parameter, S
_{v}, is velocity^{2}for 5% damping - Develop relationships for ratio S
_{v}∕a_{max}because there is a much more data for PGA than spectral ordinates and use of ratio results in relationships that are consistent over full range of magnitudes and distances. - Calculate median spectral shapes from all records with 7.8 ≤ M
_{w}≤ 8.1 (choose this because abundant data) and R < 150km and one for R > 150km. Find significant difference in spectral shape for two distance ranges. Since interest is in near-field ground motion use smoothed R < 150km spectral shape. Plot ratios [S_{v}∕a_{max}(M_{w})]∕[S_{v}∕a_{max}(M_{w}= 8)] against magnitude. Fit equation given above, fixing C_{8}= 10 (for complete saturation at M_{w}= 10) and C_{9}= 3 (average value obtained for periods > 1s). Fit C_{7}by a linear function of lnT and then fix C_{6}to yield calculated spectral amplifications for M_{w}= 8. - Calculate standard deviation using residuals of all response spectra and conclude standard deviation is governed by equation derived for PGA.

^{2}In paper conversion is made between S_{v} and spectral acceleration, S_{a}, suggesting that it is pseudo-velocity.