GEPH316 Seismic Data Processing

Field Data Workshop 2000



14 F-K Filtering
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Velocity selection


Dip/slope filtering

sudipfilt


Removing low velocity surface waves

suwind <line >s05 key=sx min=05 max=05
sufilter < s05 f=120,140,160,180 amps=1.,1.,0.,0. | suresamp dt=0.0025 nt=100 | suramp tmax=0.225 > s05.filter
suxwigb <s05.filter title='Cleaned shot at 05m' windowtitle='Cleaned shot at 05m' label1='Time (ms)' label2='Trace number'  &
suspecfk < s05.clean > s05.fk
suxwigb < s05.fk title="S05 F-K spectrum" windowtitle='S05 F-K spectrum' label1="Frequency Hz" label2="Wavenumber cycles/m" &
sudipfilt < s05.filter > s05.dip slopes=0.003,0.0036,0.004,0.005 amps=1.,1.,0.,0.
suxwigb < s05.dip title='Velocity filtered cut-off below v=263m/s' windowtitle='Velocity filtered cut-off below v=263m/s' label1='Time (ms)' label2='Trace numbers' &
supswigp < s05.dip title='Velocity filtered cut-off at v=263m/s' label1='Time (ms)' label2='Trace numbers' | lp -d mono


Wavenumber aliasing problems


Bias to avoid wavenumber aliasing

sudipfilt < s05.filter > s05.dip slopes=0.003,0.0036,0.004,0.005 amps=1.,1.,0.,0. bias=0.0038
suxwigb < s05.dip title='Low-velocity cut-off at v=263m/s with anti-alias bias' windowtitle='Low-velocity cut-off at v=263m/s with anti-alias bias' label1='Time (ms)' label2='Trace numbers' &
supswigp < s05.dip title='Low-velocity cut-off at v=286m/s with anti-alias bias' label1='Time (ms)' label2='Trace numbers' | lp -d mono

sudipfilt < s05.filter > s05.dip slopes=0.003,0.0036,0.004,0.005 amps=0.,0.,1.,1. bias=0.0038
suxwigb < s05.dip title='Low-velocity pass below v=263m/s with anti-alias bias' windowtitle='Low-velocity pass below v=263m/s with anti-alias bias' label1='Time (ms)' label2='Trace numbers' &
supswigp < s05.dip title='Low-velocity pass below v=263m/s with anti-alias bias' label1='Time (ms)' label2='Trace numbers' | lp -d mono


Removing the direct waves

sudipfilt < s05.filter slopes=0.0,0.0009,0.0011,0.0015 amps=1.,1.,0.,0. bias=0.0010 | suxwigb title='Low-velocity pass below v=1000m/s with anti-alias bias' windowtitle='Low-velocity pass below v=1000m/s with anti-alias bias' label1='Time (ms)' label2='Trace numbers' &
zap xwigb


F-K filtering the whole line

sudipfilt < line.static > line.velfilter slopes=0.003,0.0036,0.004,0.005 amps=1.,1.,0.,0. bias=0.0038
suxmovie < line.velfilter  title='Line with velocity cut-off at v=263m/s' windowtitle='Line with velocity cut-off at v=263m/s' label1='Time (ms)' label2='Trace number' &
suxmovie < line.static title='Line without velocity filtering' windowtitle='Line without velocity filtering' label1='Time (ms)' label2='Trace number' &
supsmovie < line.velfilter  title='Line with velocity cut-off at v=263m/s' label1='Time (ms)' label2='Trace number' | lp -d mono

zap xmovie
ls
cp line.static line.velfilter
rm s05.*
ls


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Comments on this information may be mailed to B.Robinson@lancaster.ac.uk
Copyright © Brian Robinson 2000. All rights reserved.
Last updated on 28/03/2000 by BR.