Motions at a Site
relationships are developed by statistical analyses performed on a large
number of records which were obtained in compatible geomorphic regions.
Most of these relationships are updated as new strong ground motion data
becomes available and many now include additional parameters such as fault
type and site soil conditions.
The relationships are grouped by region, with note to those which are
applicable only to a particular area, such as the Cascadia subduction
zone.It is important to realize that the relationships are only as good
as the data they were generated from, and therefore the relations for
Western North America are the most reliable because the database for that
area is quite rich. The relationships for Eastern and Central North America
should be used with caution because the relationships have been calibrated
with only a few events. In any event, more than one relation should be
used to predict the motions at a site. Links to coefficient tables can
be found in Appendix A.
A summary of the relationships is provided in the following table (after Abrahamson and Shedlock, 1997):
PHA = peak horizontal ground acceleration, PVA = peak vertical ground
acceleration, PHV = peak horizontal ground velocity, PVV = peak vertical
ground velocity, Sah = horizontal spectral acceleration, and Sav = vertical