orthotest.mn

.TH orthotest 1 "18 Feb 1997"
.SH NAME
orthotest \- see if a set of anisotropic elastic constants are orthorhombic
.SH SYNOPSIS
.BI "orthotest < elastic_constants
.PP
.B orthotest
expects to read from standard input an anisotropic
elastic stiffness matrix in the form of 6 numbers on each of 6 lines of input.
It finds the best-fitting orthorhombic medium to this,
and outputs:
.br
0) the input anisotropic stiffness constants,
.br
1) the elastic constants rotated so that the best-fitting orthorhombic
matrix has the X, Y, and Z axes as principal axes,
.br
2) the orthorhombic approximation to the rotated matrix,
.br
3) the orthorhombic approximation in the original coordinate system,
.br
4) the percent difference between the input stiffness matrix and the
best-fitting
orthorhombic approximation in the original coordinates (normalized by
dividing each difference by the norm of the input stiffness matrix),
.br
5) the percent difference of the anisotropic elastic constants
from orthorhombic, and
.br
6) the coordinates of the 3 principle axes in the original coordinate system,
in both cartesian and spherical notation.
.LP
Theoretically,
it is arbitrary how the three principal axes should be assigned to X, Y, and Z.
This program tries each axis in turn to see how close it is to being an axis of
transversely isotropic (TI) symmetry.
The axes are then reordered
so that the Z axis is the closest to being a TI axis of symmetry,
then Y next closest, then X furthest.
Thus, if the input medium is TI the Z axis
will always be chosen as the axis of symmetry.
(Note that if the input medium is arbitrarily anisotropic, there is
no reason to expect that the Z axis found by this program should precisely
coincide with the best-fitting TI axis found by the program titest.)
.LP
Spherical coordinates are specified using phi and theta:
.br
phi=0 is the +Z axis
.br
phi=90 theta=0 is the +X axis
.br
phi=90 theta=90 is the +Y axis
.LP
For more about what "best-fitting" means for elastic stiffness matrices, see
the article by Arts, Helbig, and Rasolofosaon in the SEG extended abstracts
for 1991, page 1534: "General Anisotropic Elastic Tensor in Rocks:
Approximation, Invariants, and Particular Directions".
.LP
See the
.B titest
man page for example input.
.SH OPTIONS
Currently there are no options or arguments.
.SH AUTHOR
This program was written by Joe Dellinger at the Amoco Tulsa Technology Center
during February 1997.
This version is copyright (c) 2005 by the Society
of Exploration Geophysicists. For more information,
see http://software.seg.org/2005/0001. You must read and accept the
terms of usage in disclaimer.txt before use.
.SH SEE ALSO
.BR titest (l)