Chiou and Youngs PEER-NGA Empirical Ground Motion Model for ...

Figure 9: Peak acceleration data from the PEER-NGA database and from TriNet (Appendix D) for
the distance range 30 ≤ RRUP ≤ 50 and the velocity range 300 ≤ VS30 ≤ 400 fit by alternative function
forms of magnitude scaling.
Other Source Effects: Most recent empirical ground motion models include a scaling term
that reflects alternative rupture styles. Typically it has been found that reverse faulting
earthquakes produce larger high frequency motions than strike-slip earthquakes. In some of
these empirical models the difference between strike-slip and reverse earthquakes diminishes
as the spectral period increases, with the motion from strike-slip earthquakes becoming larger
for period motions (e.g. Abrahamson and Silva, 1997; Campbell and Bozorgnia, 2003;
Ambraseys et al, 2005). Chiou et al. (2000) showed that when the geometric hanging wall
effect was removed from ground motion residuals by using the RRMS distance measure,
reverse-faulting earthquake still produced statistically significant higher motions than strikeslip
earthquakes. Some empirical models have shown that normal-faulting/extension regime
earthquakes produce lower ground motions than strike-slip earthquakes (e.g. Spudich et al.,
1999, Ambraseys et al. 2005) while others have included normal-faulting and strike-slip
together in a single class (e.g. Abrahamson and Silva, 1997; Silva et al., 1997; Campbell and
Bozorgnia, 2003). The potential effect of style of faulting will be examined by including
dummy variables FRV and FNM in the regression model. These parameters take on a value of
1.0 for earthquake ruptures with rake angles, λ, in the appropriate range and 0 otherwise.
Other source parameters that will be examined include depth to top of rupture ZTOR, aspect
ratio, AR, and static stress drop, ΔσS.
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