bwfi - BSU program does a grid search comparing field to synthetic MASW wave forms (C-Language Version)
bwfi [-h | infile| Vo | Vmn| Vmx| NV| Zmn | Zmx| Nz| Vhsp | Zhsp | VpVs| Rho| deltz| segsw| fmin| fmax| firvsel| tmin| tmax ]
Basic Seismic Utilities (BSU). Compares a field shot record to a grid of synthetic Rayleigh wave only synthetic records. The waves.F90 code was edited to create a Fortran subroutine (wavsub.F90) and added to the library in src/sublibF4. This is then linked to the bwfi.c main code to provide computation of the synthetics. The user provides the grid search parameters on the command line arguments. The soil profile is restricted to a 3 control point model of (depth,Vs,Vp,Den), the last point being the top of the half-space and the first the ground surface. To simplify the grid, Vs is chosen and Vp computed from a Vp/Vs ratio (constant for the profile). Mass density is also constant for the profile as both Vp and Rho are less influential than depth and Vs. One can specify the spectrum of the source and component of motion of the geophone (vertical or radial). A time window limits the the sample times included in a computation. An objective function is computed from the angle between each pair of traces (field,synthetic). That is, the windowed seismic traces are viewed as vectors in a Hilbert space, and the standard deviation of these angles about the mean angle for the shot record is the objective function. The objective function is essentially a wave form measure of agreement between a synthetic and the field data without the need to compute differences between traces field and synthetic. Further, it includes up to 9 higher modes without having to identify modes. C-Language Version.
Options
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-h |
Online help giving details on command line arguments | ||
|
infile |
Input file name for field data. | ||
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Vo |
Shear wave velocity (m/s) at surface (Z=0) FIXED. Select by considering highest frequencies in source. | ||
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Vmn |
Minimum shear wave velocity (m/s) in the search grid (can be less than Vo for velocity reversal). | ||
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Vmx |
Maximum shear wave velocity (m/s) in the search grid. | ||
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Nv |
Number of velocity steps. | ||
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Zmn |
Minimum depth of moving point in grid scan. | ||
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Zmx |
Maximum depth of the moving point in grid scan. | ||
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Nz |
Number of depth steps. There are 3 (depth,Vs) control points. The middle depth point moves on a grid, while the surface and the half-space are fixed. | ||
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Vhsp |
Velocity of half-space at the bottom of the soil profile FIXED. | ||
|
Zhsp |
Depth to top of half-space at the bottom of the soil profile FIXED. | ||
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VpVs |
The Vp to Vs ratio. A good value might be 2.0 | ||
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Rho |
Mass density for the soil (kg/m^3). This is held constant for all control points. One could edit the source code to make 3 different densities, one for each control point, thus adding 3 more arguments to a large list. | ||
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deltz |
The soil profile is 1D, horizontal layers. Elastic parameters are linearly interpolated between control points as in programs disper and waves. This parameter sets the step size for these layers. | ||
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segsw |
Switch to control whether or not *.seg synthetic shot records are output for each instance in the grid search. |
0 = No BSEGY records output.
1 = Yes output BSEGY records.
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fmin |
Minimum frequency (Hz) for synthetic records. A good value might be 0.5 Hz. | ||
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fmax |
Maximum frequency (Hz) for synthetic records. A good value might be 100 Hz. |
firvsel Switch to select component geophone.
0 = Vertical component
1 = Horizontal, radial component
|
tmin |
Minimum sample time to include in time window on seismic shot records. | ||
|
tmax |
Maximum sample time to include in time window on seismic shot records. |
NOTE:
If invoked with no options, will prompt user for input
parameters.
EXAMPLE:
bwfi 0001.seg 350. 350. 800. 3 0. 5. 4 1100. 10. 2. 2169 .1
0 .5 100. 0 0. .5
Field record 0001.seg is processed by bwfi. Minimum S-velocity (at surface) is 350 m/s. The maximum S-velocity scanned is 800 m/s. Half-space velocity is 1100. m/s, depth to top of half-space is 10 meters. The S-velocity for the middle depth control will vary in 3 steps. The top of the half-space is 5.0 meters below the surface. The middle depth control point will move in 4 depth steps. The P-velocity will be 2*Vs. The mass density will be 2169 kg/m^3. The soil profile linear interpolation of elastic parameters (not velocity) will be in 0.1 meter layers. No *.seg BSEGY synthetics will be output. Fmin = 0.5 Hz and Fmax = 100 Hz. Vertical component geophones are used. The time window extends from 0. to 0.5 seconds.
bwfixxxx.lst
named according to convention (first 4char bwfi, the next 4char are the first 4char of the input file name, suffix .lst) This file will show details of the objective function indicating which soil profile, if any, is closest match to field data.
contrplt.gp Gnuplot file
showing objective function in both contours
and color
gridpoints.gp Gnuplot file showing grid points sampled
by moving point
and surface fixed velocity with a blue dot. Also shows half-space depth and velocity with a blue point.
matcxxxx.m Octave phase
velocity dispersion curves for the grid.
matuxxxx.m Octave group velocity dispersion curves for
the grid.
disperxxxx.d Namelist file for program disper that will
compute best
fit to synthetic case.
wavesxxxx.d Namelist file for program waves that will
compute best fit
to synthetic case.
Running disper and then waves will compute the synthetic best match.
xxxxwavV.seg or
xxxxwavR.seg Synthetic shot records only if selected
by input parameters.
modelxxxx.txt Text file of best match soil profile. Can
be used for
input in Octave Rayleigh
wave inversion code (invR1.m) or with Forward problem octave code (FwdR1.m).
standard output
produces a progress bar
bhelp(1) disper(1) waves(1) wavsub(3) invR1.m(7) FwdR1.m(7)
no known bugs
Copyright © 2023 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]>