- Ground-motion model is:
where a is in gal, for method using distance partitioning b1 = 18.4, b2 = 0.941, b3 = 1.27 and k = 25 and
for ordinary one-stage method b1 = 102, b2 = 0.970, b3 = 1.68 and k = 25 (σ not given).
- Does not use PGA cutoff because PGA is, by itself, a poor index of damage in most cases.
- Mean magnitude is 5.4 and mean distance is 84.4km.
- Notes problem of regression leverage for some attenuation studies. Lots of data in fairly narrow distance
band, e.g. records from San Fernando earthquake, can dominate regression and lead to biased coefficients.
- Divides data into ten distance bands (A-J) which are 10km wide up to 60km and then 60-99.9km,
100–139.9km, 140–199.9km and ≥ 200km. Fits log 10a = bM - c to data in each band and fits
Ground-motion model to selected point set in M, R and a.
- Also fits equation using all data using normal least squares.
- Adds 52 records (3.2 ≤ M ≤ 6.5, 5 ≤ R ≤ 15km) and repeats; finds little change.