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Non-linear site amplification factor FST17

F_ST17.Rd

Implements the period-dependent, Vs30-dependent NGA-East site amplification recommendations of the 2017 PEER-report generation (nonlinear block transcribed from PEER Report 2017/05, Table 2.1; the historical "ST17" id is kept for backward compatibility) for the natural-log mean and standard deviation of the amplification factor \(F(T_n,PGA,V_{s30})\). The nonlinear sigma applies the PGA-dependent multiplier of the source model, \(\sigma_{F_{nl}} = \sigma_{f2}\,\ln((PGA_{3000}+f_3)/f_3)\) (corrected 2026-07; earlier versions used bare \(\sigma_{f2}\), making sdLnF amplitude-independent). For the final 2020 model generation see F_ST20.

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., Parker, G.A., Harmon, J.A., Atkinson, G.M., Boore, D.M., Darragh, R.B., Silva, W.J. & Hashash, Y.M.A. (2017) "Expert Panel Recommendations for Ergodic Site Amplification in Central and Eastern North America." PEER Report 2017/04 (linear model and F760 tables, transcribed from its electronic supplement).

Hashash, Y.M.A., Harmon, J., Ilhan, O., Stewart, J.P., Rathje, E.M., Campbell, K.W., Silva, W.J. & Xu, B. (2017) "Recommendation for Ergodic Nonlinear Site Amplification in Central and Eastern North America." PEER Report 2017/05 (nonlinear model, Table 2.1).