Computes site-amplified AUXtral acceleration using two modes: (A) If the input UHS contains only p == "mean", rock Sa is treated as deterministic and the dispersion in SaF comes solely from F_ST17 (sdLnF), sampled on the natural-log scale. (B) If the input UHS contains numeric quantiles (e.g., "0.10", "0.50", ...), ln Sa(Tn) is sampled from those quantiles using an empirical inverse quantile function (buildQSpline). Dependence between PGA and Sa(Tn) is represented by a Gaussian "star" copula (Baker & Jayaram, 2009) with correlation rhoBJ(Tn, T0 = 0, Rrup). For each Monte Carlo draw, F_ST17 is evaluated with the paired PGA draw, and ln SaF = ln Sa + ln F with ln F ~ Normal(muLnF, sdLnF). Independence between ln Sa and ln F is assumed.
Usage
fitSaF(
uhs,
vs30,
vref = 760,
ns = 1000,
models = "ST17",
Rrup = 100,
p_TARGET = c(0.05, 0.1, 0.16, 0.5, 0.84, 0.9, 0.95)
)Arguments
- uhs
data.table with columns Tn, p, Sa.
- vs30
target Vs30 (m/s).
- vref
reference Vs30 (m/s), default 760.
- ns
Monte Carlo size (default 1000).
- models
character. Site-response model id. Currently the only implemented model is
"ST17"; reserved for future site-response models.- Rrup
rupture distance (km) for rhoBJ() in the quantile case (default 100).
- p_TARGET
probabilities to report when only 'mean' is provided, default c(0.05, 0.10, 0.16, 0.50, 0.84, 0.90, 0.95).
Details
Requirements:
The input table must have columns Tn, p, Sa.
It must include exactly one row (Tn == 0, p == "mean") providing PGA on rock.
Output columns: Tn, p, Sa, SaF, AF, where AF = SaF / Sa. In mode (B), the same numeric p values found in the input are returned plus "mean". In mode (A), the set of p values is taken from p_TARGET plus "mean".