Non-linear site amplification factor F_ST17

Implements the period-dependent, Vs30-dependent model of Seyhan & Stewart (2014) for the natural-log mean and standard deviation of the amplification factor \(F(T_n,PGA,V_{s30})\).

Usage

F_ST17(PGA, Tn, vs30, vref = 760, Vl = 200, Vu = 2000)

Arguments

PGA

numeric vector – peak ground acceleration (in g).

Tn

numeric scalar – oscillator period (s).

vs30

numeric scalar – time-averaged shear-wave velocity to 30 m (m/s).

vref

numeric scalar – reference velocity (760 m/s or 3000 m/s), default 760.

Vl

numeric scalar – lower Vs30 bound for NL sigma interpolation (default 200).

Vu

numeric scalar – upper Vs30 bound for NL sigma interpolation (default 2000).

Value

A data.table with columns:

muLnF

natural-log mean of \(F\)

sdLnF

natural-log standard deviation of \(F\) (set to 0 when vs30 == vref)

ID

character string "ST17"

Details

If vs30 == vref, the site factor equals 1 deterministically, so the function returns muLnF = 0 and sdLnF = 0 (zero dispersion; rnorm(n, 0, 0) returns zeros and ln F = 0).

References

Stewart, J.P. & Seyhan, E. (2017) “Semi-empirical nonlinear site amplification model for global application.” Earthquake Spectra 33(1).