- See Section 2.273.
- Response parameter is pseudo-acceleration for 5% damping.
- Do not use pseudo-accelerations at periods > T
_{MAX}, the inverse of the lowest useable frequency in the NGA Flatfile. - Constant number of records to 1s, slight decrease at 2s and a rapid fall off in number of records for periods > 2s.
- For long periods very few records for small earthquakes (M < 6.5) at any distance so magnitude scaling at long periods poorly determined for small events.
- Choi and Stewart (2005) do not provide coefficients for site amplification for periods > 5s so linearly
extrapolate b
_{lin}in terms of log period by assuming relative linear site amplification to decrease. - To assign c
_{3}for entire period range fit quadratic to c_{3}s from four-event analysis with constraints for short and long periods. - No data from normal-faulting events for 10s so assume ratio of motions for normal and unspecified faults is same as for 7.5s.
- Possible underprediction of long-period motions at large distances in deep basins.
- Chi-Chi data major controlling factor for predictions for periods > 5s even for small events.