DOCUMENTATION
SYNOPSIS
PERL PROGRAM NAME: SUEA2DF - SU version of (an)elastic anisotropic 2D finite difference
AUTHOR: Juan Lorenzo (Perl module only)
DATE:
DESCRIPTION:
Version: USE
NOTES
Examples
SEISMIC UNIX NOTES
SUEA2DF - SU version of (an)elastic anisotropic 2D finite difference
forward modeling, 4th order in space
suea2df > outfile c11file= c55file= [optional parameters]
Required Parameters:
c11file=c11_file c11 voigt elasticity parameter filename
c55file=c55_file c55 voigt elasticity parameter filename
Optional Parameters:
rhofile=rho_file density filename
(if rhofile is not set, rho=1000 is assumed)
Anisotropy parameters:
aniso=0 =1 - include anisotropy parameters
mode=0 =0 output particle velocity, =1 output stresses
(snapshots only)
... the next 3 parameters become active only when aniso=1....
c13file=c13_file c13 voigt elasticity parameter filename
c33file=c33_file c33 voigt elasticity parameter filename
c15file=c15_file c15 voigt elasticity parameter filename
c35file=c35_file c35 voigt elasticity parameter filename
Attenuation parameters:
qsw=0 switch to include attenuation =1 - include
... the next parameter becomes active only when qsw=1....
qfile=Q_file Q parameter filename
dt=0.001 time sampling interval (s)
ft=0.0 first time (s)
lt=1.0 last time (s)
nx=200 number of values in slow (x-direction)
dx=10.0 spatial sampling interval (m) x-coor
fx=-1000 first x coor (m)
nz=100 number of values in fast (z)-dimension
dz=dx spatial sampling interval (m) z-coor
fz=0 firstz coor (m)
Source parameters:
sx=0 source x position (m)
sz=500 source location (m)
stype='p' source type
p: P-wave
v: velocity
pw: P plane-wave
sang=0 for stype='pw': plane wave angle
wtype='dg' wave type
dg: Gaussian derivative
ga: Gaussian
ri: Ricker
sp: spike, sp2: double spike
ts=0.05 source duration (s)
favg=50 source average frequency
Attenuation parameters:
qsw=0 switch to include attenuation =1 - include
Boundary condition parameters:
bc=10,10,10,10 Top,left,bottom,right boundary condition
=0 none
=1 symmetry
=2 free surface (top only)
>2 absorbing (value indicates width of absorbing
layer
bc_a=0.95; bc initial taper value for absorbing boundary
bc_r=0.; bc exponential factor for absorbing boundary
variables are scaled by bc_a*pow(i,-bc_r)
Optional output parameters:
sofile= name of source file
snfile= name of file containing for snapshots
snaptime= times of snapshots i.e. snaptime=0.1,0.2,0.3
vsx= x coordinate of vertical line of seismograms
hsz= z coordinate of horizontal line of seismograms
vrslfile="vsp.su" output file for vertical line of seismograms[nz][nt]
hsfile="hs.su" output file for horizontal line of seismograms[nx][nt]
tsw=0 switch to use shear stress only in non-fluid
media - may help reduce dispersion tsw=1. If
tsw=0 then standard calculation
verbose=0 =1 to print progress on screen
Notes:
1) The outfile contains information generated by the input parameters,
such as memory allocation, stability, etc. If your input file does
not work, check this file first.
The model is specified as binary files of stiffness parameters and
densities. These may be created any way the user desires. The program
unif2 or makevel may be used to generate densities, and the program
unif2aniso may be used to generate the stiffnesses. You will need to
transpose these files (stiffnesses and densities), as the input
format for suea2df assumes that the fast dimesion is the horizontal or
the x-dimension. You may do this via
transp n1=nz < c11_file > transp_c11_file
If aniso=1 then the program will expect the additional stiffnesss files.
If qsw=1 unif2anis can be used to generate the Q values on a grid
These value also need to be transposed, as with the stiffnesses. Output files (always generated) hsfile vrslfile hsfile.chd - header for hsfile vrslfile.chd - header for vrslfile hsfile.mod - model file
Output files (if requested)
sofile - ascii source file
snfile - su format snapshots file
Caveat:
A common error in using this program is to compute stiffnesses with
a specified density, but forget to specify this density as the rhofile.
Credits: UU GEOPHY Chris Juhlin 15 May 1999
Copyright (c) Uppsala University, 1998.
All rights reserved.
Parts of program use Seismic Unix Package - CSM
Changes - C. Juhlin
1. Fixed upgrading of stresses. There was an error in the coding for
the Tzz term, c15 was being used instead of c35. This only caused
problems for dipping anisotropic layers
2. Added some header information for hutput of snapshots.
3. 2001-01-30: Added option to set absorbing bc constants bc_a and bc_r
4. 2001-02-23: Corrected bug in outputting model boundaries to standard
output in
routine get_econst
5. 2001-04-26: Added option for updating velocities to only use
shear stress if material is non-fluid, this appears to reduce dispersion at
near grazing angles for fluid-solid boundary. Set tsw=1 to invoke
6. 2001-05-14: Changed loop in free-surface boundary condition for velocties
Thanks goes to Mike Holzrichter for pointing out this problem and the wrong
scaling factor in the updating.
7. 2001-05-16: Changed set_layers function to avoid negative indexing.
Thanks goes to Mike Holzrichter for pointing out this problem
8. 2001-05-17: Modified make_seis to take into account VSP geometry
correctly and not store unnecessary data.
9. 2001-08-21: Fixed set_layers so mode fills properly in depth. Earlier
versions were accessing incorrect array locations at last defined depth.
10. 2003-04-21: Fixed boundary conditions.
11. 2003-05-02: Extended the model area by half the grid spacing on the RHS.
This makes the model area symmetric allowing a plane wave source to be
introduced into the model (stype=pw). The w, txx and tzz grids contain now
one more column than the u and txz grids.
12. 2003-05-02: Added routines to allow plane waves to be introduced at a
specified angle (sang) into the model with functions add_pw_source_V and
add_pw_source_S.
13. 15 Oct 2005 -- tossed all the model building stuff. Read models
from binary files made by unif2aniso (CWP:John Stockwell)
14. 25 Feb 2008 -- Fixed attenutation option (qsw=1) so that Q values are
from binary files made by makevel or similar program
15. 1 April 2010 -- Changed free surface velocity BC back to original.
Someone had changed the scaling factor from 2.0 to 0.5 in fs4v_bc_top
Algorithm based on Juhlin (1995, Geophys. Prosp.)
and Levander (1988, Geophysics)
Attenuation included as in Graves (1996, BSSA)CHANGES and their DATES
sub Step
collects switches and assembles bash instructions by adding the program name
suea2df reads anisotropy files locally wherever the executable is run
sub note
collects switches and assembles bash instructions by adding the program name
sub clear
sub aniso
sub asw
sub bc
sub bc_a
sub bc_r
sub c11file
sub c13file
sub c15file
sub c33file
sub c35file
sub c55file
sub dt
sub dx
sub dz
sub favg
sub ft
sub fx
sub fz
sub hsfile
sub hsz
sub lt
sub mode
sub nx
sub nz
sub qfile
sub qsw
sub rho
sub rhofile
sub sang
sub snaptime
sub snfile
sub sofile
sub stype
sub sx
sub sz
sub ts
sub tsw
sub verbose
sub vrslfile
sub vsx
sub wtype
sub get_max_index
max index = number of input variables -1