- Ground-motion model is: where v = 0 for horizontal component and 1 for vertical, Δ is representative distance, S0 is correlation
radius of source function (or coherence size of source) (which can be approximated by CsT∕2, where Cs is
shear wave velocity), h is depth of sedimentary deposits beneath recording station and H is focal depth.
- Response parameter is pseudo-velocity for 0, 2, 5, 10 and 20% damping.
- Screen data to minimize possible bias due to uneven distribution of data among different magnitude
ranges and site conditions or from excessive contribution to database from several abundantly recorded
- Include term, b4(T)Δ∕100, but insignificant for most periods so remove.
- Equation only applies for Mmin ≤ M ≤ Mmax, where Mmin = -b1(T)∕(2b6(T)) and Mmax =
-(1 + b1(T))∕(2b6(T)). For M ≤ Mmin use Mmin everywhere except first term. For M ≥ Mmax use Mmax
- Use method of Trifunac (1980) for uncertainties.
- Note estimates should only be used where signal to noise ratio (based on estimated digitisation noise) not
much less than unity or slope in log-log scale is not significantly greater than -1.
- Also fit data to log 10PSV(T) = M +Att(Δ,M,T)+b1(T)M +b2(T)s+b3(T)v +b5(T)+b6(T)M2 (where
s = 0 for sediment sites, 1 for intermediate sites and 2 for basement rock sites) because depth of sediment
not always known.