- Ground-motion model is:
- Response parameter is displacement for 5, 10, 15, 20, 25 and 30% damping.
- Use three site conditions:
- Rock: V s > 750m∕s, SA = 0, SS = 0, 30–45 records.
- Stiff soil: 360 < V s ≤ 750m∕s, SA = 1, SS = 0, 56–92 records.
- Soft soil: 180 < V s ≤ 360m∕s, SA = 0, SS = 1, 32–43 records.
- Use subset of data of Ambraseys et al. (1996) (see 2.132) data with a few changes and exclusion of records
from earthquakes with Ms < 5.5 because ground motion at long periods was of interest and to increase
likelihood of acceptable single-to-noise ratio at longer periods.
- Each record individually filtered. Firstly filter record with sharp low cut-off at 0.1Hz and plot velocity
and displacement time-histories. Check, visually, whether contaminated by noise and if so increase cutoff
frequency by small amount and repeat procedure until resulting velocity and displacement time-histories
are deemed acceptable and no significant improvement is observed by further increase of cutoff frequency.
Instrument correction not applied because high frequency distortion caused by transducer characteristics
not important for displacement spectra. Only use each record for regression for periods up to 0.1s less than
filter cutoff used for that record to avoid distortion by filter, hence as period increases number of data
- Regression procedure same as Ambraseys et al. (1996), see 2.132.