WAVES
WAVES computes elastic Rayleigh waves. Start with GENDIS 9.2.5, then run DISPER 9.2.6. Run GENWAV 9.2.7 to define a simulation geometry and parameters. IMPORTANT: Make sure the frequency increments are consistent between disper and waves (see 9.2.7.1). The waves.d file will then be input to WAVES. Outputs from WAVES include:
- matu.m Octave program to plot group velocity dispersion
- matc.m Octave program to plot phase velocity dispersion (redundant with phase.m output from disper).
- m0.m Octave program to plot wavelet and spectrum.
- wavV.seg or wavR.seg seismic shot gathers in BSEGY format.
- waves.tmp listing file for waves run.
- waves.his scaled lagrangian maximum for all runs made in the current directory. Smaller the better since integrating stiff equations.
The following are some plots generated from these outputs.
Figure 52:
WAVES: Wavelet on left, group velocity dispersion on right. No significance to curve colors except that in the dispersion plot, the fundamental is Blue and higher modes are in Red. Soil representation is layer over half-space as shown in 9.2.5.1 and Figure 50 above.
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Figure 53:
WAVES: Synthetic seismograms for Vertical (wavV.seg) and horizontal (wavR.seg) motion.
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Figure 54:
Hodogram for offset 5 meters. Requires bsegin.m, segyinfo.m, and hodo2plot.m in directory with wavV.seg and wavR.seg files (see 6.0.10).
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While Rayleigh waves are often described to have elliptical retrograde motion, that is not always the case. Depending on the source depth, receiver depth, and the geologic profile, the motion can be either prograde or retrograde. In Figure 54 we see that the motion is complex, starting out with an ellipse with a sub-horizontal major axis, evolving to a vertical major axis of elliptical motion. An alternative case that illustrates retrograde elliptical motion is computed for the same waves.d. The revised disper.d uses a homogeneous half-space model (two points to describe). The result is shown in Figure 55:
show.tmp
&disper
nlay= 2,
rho= 0.1700E+04, 0.1700E+04,
mu= 0.6800E+08, 0.6800E+08,
lame= 0.9520E+09, 0.9520E+09,
zi= 0.0000E+00, 0.1000E+01,
deltz= 1.0000,
modemx=1,
nfreq=202, flo= 0.1000000E+01, delf= 0.48828122E+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 0.000 200.00 800.00 1700.0
2 1.000 200.00 800.00 1700.0
Figure 55:
Hodogram at offset 5 meters for alternative half-space soil model, see show.tmp above. Sign conventions need to be taken into account when determining type of motion.
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