gendis - Interactive program to generate namelist file for input into program disper
gendis
Compatible with Basic Seismic Utilities (BSU), this program genrates the namelist input file for program, disper, which computes Rayleigh wave dispersion curves in an elastic, 1-D layered earth. The program is interactive and prompts the user for an earth model, spectral limits, number of modes, and other signal processing requirements. Fortran 77 Version.
Example
dialog
pm@penguin:~$ gendis
enter: name of output file (
< 40 char)
disper.d
enter: sample rate
.001
enter: tmax for trace
2.0
enter: minimum frequency
1
enter: maximum frequency
150
enter: maximum mode #
9
enter: deltz step size
2
enter: number of control
3
layer( 1) enter: beta,alpha,rho,depth(top)
100,800,1600,0
layer( 2) enter: beta,alpha,rho,depth(top)
100,800,1600,2.0
layer( 3) enter: beta,alpha,rho,depth(top)
400,2000,1700,2.001
twice npts= 4096
twice tmax= 4.0960
output====>disper.d
File disper.d would then be processed by disper.
disper.d (or any other name you choose, first input)
This file will contain the content for program disper.
Example Output
The contents of the disper.d file generated by the above dialog can be viewed with the showmdl program. After the contents of the disper.d file, a brief listing of the [layer,top_depth,Vs, Vp, and Density] is also displayed.
disper.d
pm@penguin$ showmdl disper.d
show.tmp
&disper
nlay= 3,
rho=
0.1600E+04, 0.1600E+04, 0.1700E+04,
mu=
0.1600E+08, 0.1600E+08, 0.2720E+09,
lame=
0.9920E+09, 0.9920E+09, 0.6256E+10,
zi=
0.0000E+00, 0.2000E+01, 0.2001E+01,
deltz= 2.0000,
modemx=9,
nfreq=610, flo= 0.1000000E+01, delf= 0.24414061E+00,
jsmax=300, ksw=0,
pvlcty=0.0, pfreq=0.0, zend=100.0,
ofile=’disper.tmp’,
octav1=’phase.m’, octav2=’mat2.m’,
curve=’earth.crv’, /
1 0.000 100.00 800.00 1600.0
2 2.000 100.00 800.00 1600.0
3 2.001 400.00 2000.00 1700.0
sample rate
This is actually the sample interval in seconds. This establishes the frequency interval consistent with the intended aperture in the case where the disper output will be used to compute synthetic Rayleigh wave seismograms in bsegy format.
|
tmax |
The maximum time (in seconds) for synthetic seismogram traces (synthetic seismograms computed by program waves). |
frequency minimum and maximum
These are given in Hz. Recommend using more bandwidth than you are interested in if you plan on running waves on earth.crv. Too little bandwidth will produce a very ringy synthetic seismogram. You can always filter the synthetic back later.
maximum mode #
Phase velocities will be computed for modes 1 through maximum_mode. Hard-wired limit is 9 modes.
deltz step size
This is the propagator matrix minimum interval of computation in program disper. Layers may be defined as constant or as linear increases/decreases in elastic properties. The number of layers specified are actually control points. The above example builds a single layer over a half-space with 3 control (layer) points. If only the first and last control points were used in the above example, then there would be a linear increase in properties from the surface to the top of the half-space boundary. This linear increase would be achieved by a stair-case step function, each step being deltz in size. For the above example, there is no improvement in accuracy by computing the motion-stress vector in small steps through a layer of constant property.
On the other hand, if one wished to plot the motion-stress vector with some detail in a layer of constant property, a smaller deltz would be useful. The disper.d file shown is intended to compute the dispersion curves only. To plot the motion-stress vectors as a function of depth, one would edit the file, disper.d, with any text editor. The line starting with pvlcty=0.0 would be edited, replacing the default value of 0.0 with one of the phase velocities taken from the computed dispersion curves (see file disper.tmp produced by program disper). One would also edit pfreq=0.0, using the correct frequency for the desired phase velocity. Non-zero values for pvlcty and pfreq switch the program disper from computing dispersion curves to computing motion-stress vectors (the eigenfunctions).
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beta |
Shear wave velocity in m/s. |
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alpha |
P-wave velocity in m/s. |
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rho |
Mass density in kg/m^3. |
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depth |
Depth of control point in meters. |
disper(1), genwav(1), waves(1), showmdl(1), halfsp(1)
no known bugs
Copyright © 2024 by Paul Michaels
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
P. Michaels, PE. <[email protected]>