Estimating
Motions at a Site 

Toro, Abrahamson, and Schneider This
relationship is used to calculate peak ground acceleration and horizontal
spectral accelerations and is valid for moment magnitudes 5 to 8 and distances
1 to 500 km (with emphasis on the range 1 to 100 km).
The distance r_{jb}
is defined as the closest horizontal distance from the site to a point
on the earth's surface that lies directly above the rupture. Separate
coefficients are provided
for the midcontinent region group and gulf crustal region due to differences
in geologic characteristics. These relationships are for rock sites; soil
modification factors can be found in EPRI, 1993 and Silva, et al. 1996. lnPHA or Sa = C_{1} + C_{2}(M6) + C_{3}(M6)^{2} + C_{4}lnR_{M}  (C_{5}c_{4})max[ln(R_{M}/100),0]  C_{6}R_{M} where R_{M} = [r_{jb}^{2} + C_{7}^{2}]^{1/2} Links to coefficient tables can be found in Appendix A.
Other Relationships for Central and Eastern North America
