- Ground-motion model is:
where Y is in cm∕s2, a = 3.098, b = 0.3065, c = -0.07570, d = -0.8795, h = 6.910, e = 0.1452, f = 0.1893
and σ = 0.2124.
- Use three site categories:
A & B
- V s,30 > 760m∕s, 24 records ⇒ G1 = 0,G2 = 0.
- 360 < V s,30 ≤ 760m∕s, 116 records ⇒ G1 = 1,G2 = 0.
- 180 < V s,30 ≤ 360m∕s, 164 records ⇒ G1 = 0,G2 = 1.
- Uses records from ground level or in basements of structures of two stories or less, and excludes records
from dam or bridge abutments.
- Selects records which include major motion portion of strong-motion episode, represented by S wavetrain.
Excludes records triggered late on S wave or those of short duration terminating early in coda.
- Most records already corrected. Some records instrument corrected and 4-pole causal Butterworth filtered
(corner frequencies 0.1 and 25Hz). Other records instrument corrected and 4-pole or 6-pole causal
Butterworth bandpass filtered (corner frequencies 0.2 and 25Hz). All data filtered using 6-pole causal
high-pass Butterworth filter with corner frequency 0.2Hz and velocity and displacement curves examined.
- Uses method of Campbell (1997) to reduce bias due to non-triggered instruments, for some recent shocks.
Firstly uses all data to determine minimum distances (which are functions of magnitude and site condition)
at which 16th percentile values of PGA are < 0.02g[0.2m∕s] (corresponding to 0.01g[0.1m∕s] vertical
component trigger threshold). Next delete records from larger distances and repeat regression.
- Check residuals against distance and magnitude for each site class; find no obvious non-normal magnitude
or distance dependent trends.