Estimating
Motions at a Site 
This
relationship is used to calculate peak ground acceleration and horizontal
spectral accelerations and is valid for moment magnitudes 4 to 9.5, distances
1 to 100 km, and depths 1 to 150 km.
The distance r_{rup}
is defined as the closest distance from the site to the rupture surface.
For
rock: For
soil: where Z_{T} = depth in km Links to coefficient tables can be found in Appendix A.
