- Ground-motion model is [same as Fukushima et al. (2003)]:
δj = 1 for jth site class and 0 otherwise.
- Use five site categories:
- Site natural period TG < 0.2s, V s,30 > 600m∕s, NEHRP classes A+B. 23 sites.
- Site natural period 0.2 ≤ TG < 0.6s, 200 ≤ V s,30 < 600m∕s, NEHRP classes C+D. 100 sites.
- Site natural period TG ≥ 0.6s, V s,30 ≤ 200m∕s, NEHRP class E. 95 sites.
- Unknown site natural period, V s,30 > 800m∕s, NEHRP classes A+B. 44 sites.
- Unknown site natural period, 300 ≤ V s,30 < 800m∕s, NEHRP class C. 79 sites.
Manually classify stations using the predominant period computed using average horizontal-to-vertical
(H/V) response spectral ratios using similar approach to Zhao et al. (2006) and also mean residuals
w.r.t. equations of Fukushima et al. (2003). Reclassify stations of Fukushima et al. (2003), who used
rock/soil classes. Some (36%) stations cannot be classified (due to, e.g., broadband amplification) using this
approach so retain rock/soil classes for these records. Use this approach since limited geotechnical data is
available for most sites in their dataset. Only roughly 30% of stations have multiple records so the average
H/V ratios are not statistically robust so do not use automatic classification approach. Each co-author
independently classified stations. About 90% of classifications agreed. After discussion the stations were
reclassified. Originally used same categories as Zhao et al. (2006) but find their class SC-III too narrow so
combine it with their SC-II to form SC-2. Find similar average ratios for the different categories as Zhao
et al. (2006).
- Response parameter is acceleration for 5% damping.
- Use data and regression method of Fukushima et al. (2003). Eliminate data from two stations of
Fukushima et al. (2003) because of suspected soil-structure interaction.
- Coefficients not reported since focus of article is the site classification procedure and its impact on predicted
response spectra and not to propose a new model for seismic hazard assessment.
- Records filtered with cut-offs at 0.25 and 25Hz therefore present results up to 3s to avoid filter effects.
- Find roughly 2% reduction in standard deviation using classification scheme compared to rock/soil scheme.