PoR_azi() R function from [tectonicr]

Azimuth Conversion from Geographical to PoR Coordinate Reference System

Transforms azimuths and models the direction of maximum horizontal stress $SHmax$ in the Euler pole (Pole of Rotation) coordinate reference system. When type of plate boundary is given, it also gives the deviation from the theoretically predicted azimuth of $SHmax$ , the circular distance, and the normalized $chi-squared$ statistics.


PoR_azimuth(x, PoR, axial = TRUE)

PoR_shmax(x, PoR, type = c("none", "in", "out", "right", "left"))

Arguments

x: sf object or a data.frame containing the coordinates of the point(s) (lat, lon). x must contain the direction of $SHmax$ as column azi and its standard deviation as unc (the latter is optional)
PoR: "data.frame" or object of class "euler.pole"

containing the geographical coordinates of the Euler pole
axial: logical. Whether the azimuth is axial (0-180) or directional (0-360).
type: Character. Type of plate boundary (optional). Can be "out", "in", "right", or "left" for outward, inward, right-lateral, or left-lateral moving plate boundaries, respectively. If "none" (the default), only the PoR-equivalent azimuth is returned.

Returns

PoR_azimuth returns numeric vector of the transformed azimuth in degrees. PoR_shmax returns either a numeric vector of the azimuths in the transformed coordinate system (in degrees), or a "data.frame" with

azi.PoR: the transformed azimuths (in degrees),
prd: the predicted azimuths (in degrees),
dev: the deviation between the transformed and the predicted azimuth (in degrees),
nchisq: the Norm $chi-squared$ test statistic, and
cdist: the angular distance between the transformed and the predicted azimuth.

Details

The azimuth of $SHmax$ in the pole of rotation reference system is approximate 0 (or 180), 45, 90, 135 degrees if the stress is sourced by an outward, sinistral, inward, or dextral moving plate boundary, respectively. directions of $SHmax$ with respect to the four plate boundary types.

Examples


data("nuvel1")
# North America relative to Pacific plate:
PoR <- subset(nuvel1, nuvel1$plate.rot == "na")

data("san_andreas")
res <- PoR_shmax(san_andreas, PoR, type = "right")
head(res)

References

Stephan, T., Enkelmann, E., and Kroner, U. "Analyzing the horizontal orientation of the crustal stress adjacent to plate boundaries". Sci Rep 13. 15590 (2023). tools:::Rd_expr_doi("10.1038/s41598-023-42433-2") .

PoR_azi function