SUEA2DF - SU version of (an)elastic anisotropic 2D finite difference forward modeling suea2df > outfile nxl= xl= zl= rhol= vpl= vsl= [optional parameters] Required Parameters: nxl= number of locations to define model xl= model locations in horizontal direction zl= model depths rhol= model rho at xl,zl vpl= model vp at xl,zl vsl= model vs at xl,zl Optional Parameters: dt=0.001 time sampling interval (s) ft=0.0 first time (s) lt=1.0 last time (s) dx=10.0 spatial sampling intrval (m) x-coor dz=dx spatial sampling intrval (m) z-coor xmin=-1000 first x coor (m) xmax=1000 last x coor (m) zmin=0 top z coor (m) zmax=1000 bottom z coor (m) sx=0,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 length (s) favg=50 source average frequency ql= model q at xl,zl qsw=0 switch to include attenuation =1 - include epl= anisotropy ep at xl,zl dsl= anisotropy ds at xl,zl anl= anisotropy angle at xl,zl asw=0 switch to include anisotropy =1 - include msw=0 model type (=0 - field; =1 - layer) mode=0 =0 output particle velocity, =1 output stresses (snapshots only) sofile= name of source file efile= name of file to output model to if desired 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 vsfile='vsp.su' output file for vertical line of seismograms[nz][nt] hsfile='ss.su' output file for horizontal line of seismograms[nx][nt] 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) 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 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 zl,vpl,vsl,rhol specify elastic constants as function of depth. Linear interpolation and constant extrapolation is used to determine constants at depths not specified. Values specified in depth must increase monotonically. If qsw=1 a ql array must be specified If asw=1 epl,dsl and anl arrays must be specified epl and dsl are epsilon and delstar in Thomson (1986, Geophys.) anl is the angle the anisotropy makes with the horizontal Output files (always generated) hsfile vsfile hsfile.chd - header for hsfile vsfile.chd - header for vsfile hsfile.mod - model file Output files (if requested) sofile - ascii source file efile - binary elastic constants file snfile - su format snapshots file 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, e15 was being used instead of e35. This only caused probelms for dipping anisotropic layers 2. Added some header information for output 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. Alogrithm based on Juhlin (1995, Geophys. Prosp.) and Levander (1988, Geophysics) Attenuation included as in Graves (1996, BSSA)