- Ground-motion model is (from definition of local magnitude scale): where log A0(R) is an empirically determined attenuation function from Richter (1958) used for calculation
of ML, p is confidence level and v is component direction (v = 0 for horizontal and 1 for vertical). log A0(R)
not given here due to lack of space.
- Response parameter is pseudo-velocity for 0, 2, 5, 10 and 20% damping.
- Uses three site categories:
s = 0
- Alluvium. 63% of data.
s = 1
- Intermediate. 23% of data. Notes that ideally would not need but had to be introduced because in
some cases difficult to make a choice in complex geological environment or because of insufficient
s = 2
- Basement rock. 8% of data.
- Use same data as Trifunac and Anderson (1977). See Section 4.4.
- Use same regression method as Trifunac and Anderson (1977). See Section 4.4.
- Equation constrained to interval Mmin ≤ M ≤ Mmax where Mmin = -b(T)∕2f(T) and Mmax =
[1-b(T)]∕2f(T). For M > Mmax replace M by Mmax everywhere and for M < Mmin replace M by Mmin
in b(T)M and f(T)M2. This gives linear growth for M < Mmin, parabolic growth for Mmin ≤ M ≤ Mmax
and constant amplitude for M > Mmax.
- 98 records from San Fernando earthquake (9/2/1971) but regression method eliminated 70% of these before
computing the coefficients.
- Epicentral distance used for simplicity, consistency with earlier studies and for lack of significantly better
choice. Distance measure chosen has small effect whenever epicentral distance greater than several source
- Notes that recording and processing noise in signal means that quality of coefficients diminishes for T > 2s.
Equations not recommended for periods longer than those for which selected spectral amplitudes plotted.
- Notes that equations should be considered only as preliminary and an empirical approximation to a
complicated physical problem.
- Notes that data are limited to narrow magnitude interval, most data comes from alluvium sites and about
half comes from one earthquake.
- Only gives coefficients for 11 periods. Graphs of coefficients for other periods.