okada85: Okada Fault Deformation Model
In geophys: Geophysics, Continuum Mechanics, Gravity Modeling

Description Usage Arguments Details Value Note Author(s) References See Also Examples

Calculate the deformation due to a fault based on Okada 1985 code.

1 2	okada85(e = 0, n = 0, depth = 0, strike = 20, dip = 20, L = 5, W = 3, rake = 20, slip = 1, U3 = 1, nu = 0.25)

`e`	vector or matrix, Easting Observation, km
`n`	vector or matrix, Northing Observation, km
`depth`	depth of fault
`strike`	degrees, strike of fault, measured from north
`dip`	degrees, strike of fault, measured from horizontal
`L`	Length, km
`W`	Width, km
`rake`	rake (degrees)
`slip`	slip
`U3`	dilitation (m)
`nu`	Poisson's ration, default=0.25

Computes displacements, tilts and strains at the surface of an elastic half-space, due to a dislocation defined by RAKE, SLIP, and OPEN on a rectangular fault defined by orientation STRIKE and DIP, and size LENGTH and WIDTH. The fault centroid is located (0,0,-DEPTH).

R-Code is a translation of original Matlab code by Francois Beauducel. UNC student Lan Ngo worked on the first version and J. M. Lees tested, verified and finalized the package.

list:

`uE`	East deformation
`uN`	North deformation
`uZ`	Vertical deformation
`uZE`	tilt vertical east
`uZN`	tilt vertical north
`uNN`	horizontal strains North-North
`uNE`	horizontal strains North-East
`uEN`	horizontal strains East-North
`uEE`	horizontal strains East-East

Units should be in km.

Note that vertical strain components can be obtained with following equations: uNZ = -uZN; uEZ = -uZE; uZZ = -(uEE + uNN)*NU/(1-NU);

Be careful about the definition of strike: seems that here the strike may be measured positive north of east, not east of north as stated in the documentation above.

Jonathan M. Lees<jonathan.lees@unc.edu>

Aki K., and P. G. Richards (1980) (ISBN-13: 978-1891389634) Quantitative seismology, Freemann & Co, New York.

Okada Y., Surface deformation due to shear and tensile faults in a half-space, Bull. Seismol. Soc. Am., 75:4, 1135-1154, 1985.

Acknowledgments: Francois Beauducel, Dmitry Nicolsky, University of Alaska

mogi1, mogiM

library(RPMG)

EX = seq(from=-10, to=10, length=50)
WHY = seq(from=-10, to=10, length=50)
M = RPMG::meshgrid(EX, WHY )

OKout  = okada85(M$x, M$y,2,30,70,5,3,-45,1,1) 
old.par <- par(no.readonly = TRUE) 

par(mfrow=c(2, 2))

image(EX, WHY, OKout$uN, col=terrain.colors(100) ,
asp=1, main="uN" );contour(EX, WHY, OKout$uN, add=TRUE)

image(EX, WHY, OKout$uE, col=terrain.colors(100) ,
asp=1 , main="uE" );contour(EX, WHY, OKout$uE, add=TRUE)

image(EX, WHY, OKout$uZ, col=terrain.colors(100) ,
asp=1, main="uZ" );contour(EX, WHY, OKout$uZ,  add=TRUE)

plot(EX, OKout$uZ[, 25 ])


par(old.par)