# CY08 Sub-Functions {nga}

### Description

The sub-functions needed to estimate ground motions using the Chiou & Youngs NGA model. These functions are called by the main function used for calculations, `Sa.cy`

.

### Usage

LnYref.cy(M, Rrup, Rjb, Rx, Ztor, dip, Frv, Fnm, Fhw, AS, T) NL.cy(Yref, Vs30, T) Sigma.cy(M, Yref, Vs30, VsFlag, AS, T) Tau.cy(M, T) SigmaTot.cy(M, Yref, Vs30, VsFlag, AS, T) SaMedian.cy(M, Rjb, Rrup, Rx, Ztor, Frv, Fnm, AS, Fhw, dip, Vs30, Z1.0, T)

### Arguments

- M
- Moment magnitude of earthquake.
- Rjb
- Horizontal distance to the surface projection of the rupture plane; Joyner-Boore distance (km).
- Rrup
- Closest distance to the rupture plane; rupture distance (km).
- Rx
- Horizontal distance to the surface projection of the top edge of the rupture plane, measured perpendicular to the strike; site coordinate (km).
- Ztor
- Depth to top of rupture (km).
- Frv
- Reverse style-of-faulting flag; equal to 1 for reverse faulting (
`30 <= rake <= 150 deg`

), and 0 otherwise. - Fnm
- Normal style-of-faulting flag; equal to 1 for normal faulting (
`-120 <= rake <= -60 deg`

), and 0 otherwise. - AS
- Aftershock flag; equal to 1 for aftershocks and 0 for mainshocks.
- Fhw
- Hanging wall flag; equal to 1 for sites on the hanging wall side of the fault (
`Rx >= 0`

) and 0 otherwise. - dip
- Fault dip angle (deg).
- Vs30
- Time-averaged shear wave velocity over a subsurface depth of 30 meters (m/s).
- VsFlag
- Flag variable indicating how
`Vs30`

is obtained; equal to 1 if`Vs30`

is measured, and 0 if`Vs30`

is estimated or inferred. - Z1.0
- Depth to Vs = 1.0 km/s (m).
- Yref
- Median ground motion for the reference rock site condition (g).
- T
- Spectral period (sec). Use 0 for PGA and -1 for PGV.

### Details

`LnYref.cy`

- Median ground motion on reference rock site (Eqn 13a of Chiou and Youngs (2008)).
`NL.cy`

- Nonlinear site response term (Eqns 10 and 21).
`Sigma.cy`

- Intra-event standard deviation (Eqn 20).
`Tau.cy`

- Inter-event standard deviation (Eqn 19).
`SigmaTot.cy`

- Total standard deviation (Eqn 21).
`SaMedian.cy`

- Median estimate of ground motion, with site response (Eqn 13b).

### Values

Returns values of the sub-functions for the Chiou & Youngs NGA model. The outputs of the functions are in log space, with the exception of `SaMedian.cy`

, which outputs values in g (for Sa and PGA) or cm/s (for PGV).

### References

Chiou, B. S.-J., and R. R. Youngs (2008). An NGA Model for the Average Horizontal Component of Peak Ground Motion and Response Spectra. *Earthquake Spectra* **24,** 173--215.

### See Also

`coefs`

, `coefs.t.cy`

, `periods.cy`

, `Sa.cy`

, `Sa.nga`

.

Documentation reproduced from package nga, version 1.4-1. License: GPL-2