Predict Slip Direction for Given Faults and Stress Tensor

Forward problem: given a reduced stress tensor and one or more fault planes, predict the slip direction(s) under the Wallace-Bott hypothesis.

Usage

sigma2slip(sigma, normals, tol = NULL)

Arguments

sigma

matrix of object of class "ellipsoid". 3x3 reduced stress tensor (as returned by sigma from slip_inversion())

normals

object of class "Plane" of "Vec3"

tol

numeric. Convergence tolerance on max absolute change in TR elements between iterations. Defaults to getOption("structr.tol").

Value

list.

slip_dirs

Vec3 or Ray object of predicted slip direction vectors

tau_mag

length-N vector of shear traction magnitudes \(|\tau|\) (unnormalised)

degenerate

logical. TRUE where \(|\tau|\) < tol (plane contains a principal stress axis — slip direction undefined)

See also

slip_inversion(); stereo_stress_grid()

Examples

sigma <- reduced_stress(angelier1990$AVB)
normals <- Plane(120, 50)
s <- sigma2slip(sigma, normals)
print(s)
#> $slip_dirs
#> Ray object (n = 1):
#>   azimuth    plunge 
#> 137.47336  48.66218 
#> 
#> $tau_mag
#> [1] 0.9331311
#> 
#> $degenerate
#> [1] FALSE
#> 

plot(normals)
pr <- sigma2stress(sigma)
points(pr$axes, col = 2:4, pch = 16)
text(pr$axes, label = rownames(pr$axes), col = 2:4, adj = -.25)
stereo_arrows(s$slip_dirs, sense = -sign(s$slip_dirs[, 2]))