waves

NAME
SYNOPSIS
DESCRIPTION
Namelist Variables
FILES
SEE ALSO
BUGS
COPYRIGHT
AUTHOR

NAME

waves - Computes Rayleigh Waves vertical or horizontal displacement time series

SYNOPSIS

waves [ infile ]

DESCRIPTION

Compatible with Basic Seismic Utilities (BSU), this program computes Rayleigh waves from the dispersion curve which is first computed by program disper. The input file, waves.d, contains namelist parameters required by waves.
One begins by generating the input file first. Run the program genwav. The output of genwav is usually called waves.d and becomes the input to waves. The output of waves includes synthetic Rayleigh wave seismic records. These seismic files are BSU compatible. Fortran 90 Version.

Namelist Variables

&waves Namelist
ksw = 0 plot dispersion: phase velocity vs. frequency

= 1 plot dispersion: wavenumber vs. frequency

stepz = number of samples in the shortest S-wave length modeled

The shortest wavelength=(slowest S-velocity)/(fmax). See BUGS note below for potential traps, and how this parameter can be changed to fix a problem. Default is 20 samples/wavelength.

modes = 1,2,3,4,5,6,7,8,9 (include all modes up to 9)

= 1,0,0,0,0,0,0,0,0 (include only fundamental, even if more modes available)

fmin = minimum frequency to include (will sync to closest value in
earth.crv
file)
fmax = maximum frequency to include (limited by what is available in
earth.crv
)

NOTE: Parameters fmin and fmax control the generation of the minimum phase wavelet (scalar source moment) for the synthetic seismogram. The bandwidth of the wavelet is internally reduced so that the spectrum is near zero within the (fmin,fmax) bandwidth contained in the curve file (typically earth.crv). The wavelet minimum frequency is set to 4*fmin, and the wavelet maximum frequency is set at fmax/2. This prevents a ringing wavelet.

fsamin = sample interval in seconds. MUST agree with disper run.

To ensure agreement with disper dispersion computation, specify the same aperture for both programs. That is, if the tmax=maximum trace time and sample interval are the same, all will be well. Thus, earth.crv file will have correct frequency increment for computing a synthetic seismogram in waves; deltf=1/(N*fsamin).

curve = name of dispersion curve file produced by disper run. Example,
earth.crv

mapmat = 0 generate plot programs in Octave/Matlab format.

= 1 generate plot programs in Scilab format.

scilb1 = name of file for phase velocity /or wavenumber dispersion
plot, if mapmat=1

example: sclb1=’matc.sci’

scilb2 = name of file for group velocity dispersion plot, if mapmat=1

example: scilb2=’matu.sci’

matlb1 = name of file for phase velocity /or wavenumber dispersion
plot, if mapmat=0

example: matlb1=’matc.m’

matlb2 = name of file for group velocity dispersion plot, if mapmat=0

example: matlb1=’matu.m’

irvsel = 0 generate a vertical component displacement synthetic
seismogram

= 1 generate a radial, horizontal component displacement synthetic seismogram

ofile = name of output listing file documenting run.

&source Namelist
tm = moment tensor specifying radiation pattern, 3x3
sz, sy, sx = the depth, y-coordinate, x-coordinate of source

&recvr Namelist
nrec = number of receivers
rz = receiver depths (+down)
ry = receiver y-coordinates
rx = receiver x-coordinates (typically require nrec number of these

Options

infile

This is the name of the file with the namelists. Typically this file is called waves.d, it is easily generated by the program genwav.

NOTE:
If invoked with no options, will prompt user for the input file name

EXAMPLE:
waves waves.d

File waves.d is processed by waves.

FILES

wavV.seg

If vertical motion is selected, this is the file with the time series data in bsegy format.

wavR.seg

If horizontal motion is selected, this is the file with the time series data in bsegy format.

standard output

produces a listing on the fly of the dispersion curve, including Group and Phase velocities

waves.tmp

Saved output very similar to standard output, gives input parameters and listing of the dispersion curves.

matc.m

phase velocity dispersion plotting procedure for execution by Octave

matu.m

group velocity dispersion plotting procedure for execution by Octave

m0.m

Octave file plots scalar source moment (wavelet) in time, and spectrum.

waves.his

Text file records maximum Lagrangian for the run, and at which frequency.

SEE ALSO

gendis(1), genwave(1), disper(1), showmdl(1), halfsp(1)

BUGS

no known bugs, but there are some potential parameter selection traps. See documentation for details. One thing to look for is a large lagrangian with a glitch in the group velocity plot. This can occur when modeling an abrupt discontinuity between thick layers by using two control points very close together (for the discontinuity). Program waves has to compute numerical energy integrals with a finer depth interval than may have been used in the preceeding disper run. This interval is a function of the maximum frequency and affects all frequencies. The current version uses the stepz parameter set to 20. This sets the numerical integration interval to 20 samples per shortest wavelength of the SV wave component (determined by fmax and slowest S-wave velocity in the model), and if this integration interval is less than the width of the discontinuity, the implied model changes and becomes inconsistent with the disper run. In other words, the discontinuity becomes subdivided into additional layers with different transitional velocities across what would otherwise be an abrupt discontinuity. Corrective action is to either make the discontinuity more abrupt (move control points closer together), OR to decrease the stepz parameter (which may unfortunately increase the lagrangian, but often is not serious).

COPYRIGHT

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.

AUTHOR

P. Michaels, PE. <paulmichaels@.boisestate.edu>