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lab3
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lab3
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#!/bin/bash
# I/P file : farfield signature is provided as a segy file "farfield.sgy" & "ntgather.su" is other I/P file
# copying all inputs file in input_files directory
test -d input_files || mkdir input_files
cp farfield.sgy ntgather.su lab3 Lab3_2018.pdf DOUBT -t /home/kantm/seismiclab/Viking_graben/lab3/input_files
# sampling interval for the farfield wavelet is 1ms
# verbose is just a bash-command telling in terminal what is done by each excuted command
segyread tape=farfield.sgy verbose=1 | sushw key=dt a=1000 > farfield.su
supswigb <farfield.su label1="Time (s)" label2="Trace" title="Farfield" perc=99 > farfield.ps
# SUSHW - Set Header (one or more) Words using trace number, mod and
sufft < farfield.su | suamp mode=amp >farfield_fft.su
supswigb <farfield_fft.su label1="Frequency (in Hz)" label2="Amplitude" title="FFT of Farfield" perc=99 > farfield_fft.ps
# sufft : fft real time traces to complex frequency traces
# suamp : output amp, phase, real or imag trace from
# mode=amp: output amplitude traces
# The farfield wavelet is sampled at 1 ms and the seismic data is sampled at 4 ms.
# We should down_sample the farfield wavelet.
# But before we down_sample, we need to apply a low-pass filter (why? -> else frequency above nyquist will be folded back)
sufilter < farfield.su f=90,110 amps=1,0 > farfield_filt.su
supswigb <farfield_filt.su label1="Time (s)" label2="Trace" title="With Filter in Farfield" perc=99 > farfield_filt.ps
# sufilter : applies a zero-phase, sine-squared tapered filter
# f= array of filter frequency
# amps= array of filter amplitudes
sufft < farfield_filt.su | suamp mode=amp >farfield_filt_fft.su
supswigb <farfield_filt_fft.su label1="Frequency (in Hz)" label2="Amplitude" title="FFT of Farfield with Filter applied" perc=99 > farfield_filt_fft.ps
# have removed high frequencies, now ready to do down_sampling
suresamp < farfield_filt.su dt=0.004 nt=150 > farfield_resamp.su
# you might have observed that the far-field wavelet is not minimum phase
# convert the wavelet into minimum phase
suminphase < farfield_resamp.su sign2=-1 > farfield_minphs.su
# The same filter should be applied to the data to convert it to minimum phase
# This shaping operation is also called signature deconvolution (lets do it)
sugain < ntgather.su agc=1 > agc_ntgather.su
suchw < agc_ntgather.su >agc_ntg_hdrs1.su key1=tstat a=2 b=0 c=0 d=1
sustatic <agc_ntg_hdrs1.su >stat_agc_ntgather.su hdrs=1
sushape < stat_agc_ntgather.su wfile=farfield_resamp.su dfile=farfield_minphs.su showshaper=1 nshape=1500 2>shaper.asc > ntgather_minphs.su
# sushape : wiener shaping filter
# wfile : file containg input wavelet in SU(SEGY trace) format
# dfile : file containing desired output wavelet in SU format
# nshape : length of shaping filter
# showshaper=1 : show shaping filter
suacor < ntgather.su ntout=1001 > ntgather_acor.su
supswigb <ntgather_acor.su label1="Time (s)" label2="Trace" title="auto correlation of NT gathers" f1=-2.0 perc=99 > ntgather_acor.ps
# suacor : auto-correlation
# ntout : number of time samples output
# f1=-2.0 first sample in the fast dimension