- Ground-motion model is:
- Response parameter is velocity for unspecified
^{1}damping. - Do regression iteratively. Assume a(ω), b(ω) and c(ω). Find amplification factors, G
_{i}(ω), for each response spectra, R_{i}(ω): G_{i}= R_{i}(ω)∕S_{V 0}. Calculate amplification factor, G, for each site: G = . Estimate bedrock spectrum, B_{i}(ω), for each record: B_{i}(ω) = R_{i}(ω)∕G(ω). Find a(ω), b(ω) and c(ω) by least squares. Repeat these steps until convergence. Hence find attenuation relation for bedrock and amplification function for each site.

^{1}It is probably 5%.