% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/rhoBJ.R
\name{rhoBJ}
\alias{rhoBJ}
\title{Baker and Jayaram (2008) inter-period correlation model}
\usage{
rhoBJ(Tn, T0 = 0.01, Rrup = 100)
}
\arguments{
\item{Tn}{Numeric scalar. Target spectral period in seconds.}

\item{T0}{Numeric scalar. Reference period in seconds. Default 0.01
(used as a numerical proxy for PGA). Values <= 0 are silently
converted to 0.01.}

\item{Rrup}{Numeric scalar. Not used; retained for backward compatibility.}
}
\value{
Numeric scalar correlation coefficient rho(T0, Tn).
}
\description{
Computes the Pearson correlation coefficient between the residuals of
ln(Sa) at two oscillator periods, using the canonical predictive equation
of Baker and Jayaram (2008), Earthquake Spectra 24(1), 299-317
(DOI 10.1193/1.2857544), Eqs. 5 and 6 verbatim.
}
\details{
The model has no dependence on rupture distance or magnitude.
\code{Rrup} is retained for signature compatibility and is silently ignored.
Periods of zero are treated as 0.01 s (standard PGA proxy in B&J 2008).

Form (Eqs. 5-6 of B&J 2008):
C1 = 1 - cos(pi/2 - 0.366 * ln(Tmax / max(Tmin, 0.109)))
C2 = (1 - 0.105 * (1 - 1/(1 + exp(100*Tmax - 5))) * (Tmax-Tmin)/(Tmax-0.0099))
if Tmax < 0.2; else 0
C3 = C2 if Tmax < 0.109; else C1
C4 = C1 + 0.5 * (sqrt(C3) - C3) * (1 + cos(pi * Tmin / 0.109))

rho = C2          if Tmax < 0.109
= C1          else if Tmin > 0.109
= min(C2, C4) else if Tmax < 0.2
= C4          otherwise

Validity: 0.01 <= T1, T2 <= 10 s.
}
\examples{
rhoBJ(Tn = 0.3, T0 = 0.01)   # rho(PGA, 0.3 s)
rhoBJ(Tn = 1.0, T0 = 0.5)

}
\references{
Baker, J. W. & Jayaram, N. (2008). Correlation of Spectral Acceleration
Values from NGA Ground Motion Models. Earthquake Spectra, 24(1), 299-317.
DOI: 10.1193/1.2857544.
}
