- Ground-motion model is:
where PGA is in cm∕s2, θ

_{0}= 0.4063, θ_{1}= 0.7936, θ_{2}= -0.02146, θ_{3}= 0.0004183, θ_{4}= -1.7056, θ_{5}= 5.7814, θ_{6}= -0.05656, σ_{e}= 0.17561 (inter-event), σ_{s}= 0.17065 (inter-site), σ_{r}= 0.19925 (residual) and σ_{T }= 0.31569 (total). - Use data from 204 sites.
- Use regression approach of Chen and Tsai (2002) to separate variance into 3 components: inter-event, inter-site and residual.
- Plot inter-event residuals (event terms) of shallow (focal depth ≤ 30km) earthquakes w.r.t. M
_{L}and on map. Find residuals are independent of magnitude and not correlated with location. - Plot inter-site residuals (site terms) on map. Find that these are more coherent in space, which are generally consistent with local geology (e.g. positive terms for alluvium sites.).
- Plot direct travel paths from all shallow earthquakes to associated sites. Expect that variability of
path-to-path component of error would be similar to event terms or at least not smaller than site terms.
Hence assume σ
_{P }= 0.17321 (path component) and compute refined σs. - Show that by specifying a priori the variability of path-to-path component that this can be removed from residual.