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COmig.m
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%{
Comig.m - Common offset Kirchhoff migration in time and depth.
Copyright (C) 2013 Jesper S Dramsch, Matthias Schneider, Dela Spickermann, Jan Walda
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 3 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, see <http://www.gnu.org/licenses/>.
%}
clear all % Clear workspace
close all % Close figures
clc % Clear command line window
format long % Double precision
tStart = tic; % runtime measurement
dcmp = 20; % CMP-Distance [m]
dt = 2e-3; % Samplinginterval [s]
nt = 1001; % Number of samples
ns = 101; % Number of traces
nh = 5; % Number of offsets
Fs = 1/dt; % Frequency sampling [Hz]
hmax = 1000; % Maximum half-offset [m]
dh = 250; % half-offset increment [m]
vmin = 2754; % Minimum test velocity [m/s]
vmax = 2754; % Maximum test velocity [m/s]
vfinal = 2754; % Final migration velocity [m/s]
dv = 100; % Velocity increment [m/s]
aper = 200; % Aperturewidth [m]
dz = 4; % Depthsampling increment [m]
flag_interp = 1; % 1 = use interpolation, 0 = use rounding
kirch_time=0; % Time Migration
kirch_depth=1; % Depth Migration
%% Open file
% Original data
filename = 'data-6/SEIS-orig';
fid = fopen(filename,'r');
data = reshape(fread(fid, [nt nh*ns],'single'),nt,ns,nh);
fclose(fid);
% With sqrt{-i omega} filtered data
filenamefilt = 'data-6/SEIS-filt';
fidfilt = fopen(filenamefilt,'r');
filtdata = reshape(fread(fidfilt, [nt nh*ns],'single'),nt,ns,nh);
fclose(fidfilt);
%% Input Plots
% Compare max amplitudes of each CMP in original data
mig_graphs('OffsetLine',data,((1:ns)-1)*dcmp,'ampsorig')
% Compare max amplitudes of each CMP in original data
mig_graphs('OffsetLine',filtdata,((1:ns)-1)*dcmp,'ampsfilt')
% Input signal normalized
mig_graphs('CompLine','Filtered data',filtdata(:,51,1)/max(filtdata(:,51,1)),'Original data',data(:,51,1)/max(data(:,51,1)),((1:nt)-1)*dcmp,'Zeit [s]','Normalisierte Amplitude','waveletnorm')
% Input signal not normalized
mig_graphs('CompLine','Filtered data',filtdata(:,51,1),'Original data',data(:,51,1),((1:nt)-1)*dcmp,'Zeit [s]','Amplitude','waveletorig')
%% Frequency analysis
NFFT = 2^nextpow2(nt); % calculate next 2^n to prepare adta for FFT
fdata = fft(mean(data(:,:,1),2),NFFT)/nt; % FFT of extended dataset
faxis = Fs/2*linspace(0,1,NFFT/2+1); % Skaling of the x-axis
%% Frequency Plot
mig_graphs('SingleLine',abs(fdata(1:length(faxis)))/max(abs(fdata(1:length(faxis)))),faxis,'Frequencz [Hz]','Normalized Amplitude','freq')
%% Kirchhoff migration
%% discretizing and initializing
h=0:dh:hmax; % half offset
t_orig=0:dt:((nt-1)*dt);
i_v=0;
aper_half = round(.5*aper/dcmp); % half aperture
% x-sampling = cmp-sampling
%% Loop over velocities
for v = vmin:dv:vmax;
i_v = i_v+1;
t_depth=t_orig*v*0.5; % TWT-time to depth conversion
zmax = max(t_depth); % Max depth [m]
z=0:dz:zmax; % Depthsampling
z_len = length(z);
Kirchhofftime(1:nt,1:ns,1:nh)=0; % (time, CMP, halfoffset)
%Kirchhoffdepth(1:z_len,1:ns,1:nh)=0;% (depth, CMP, halfoffset)
mig(1:z_len,1:ns)=0; % stacking result
filt_interp(1:z_len,1:ns,1:nh)=0;
%% loop over half offsets
for i_h = 1:nh
disp('half offset'); disp((i_h-1)*dh);
% to get the feeling it still runs when using
% interpolation at zdiff
if kirch_time == 1
[Kirchhofftime(:,:,i_h), Skala(:,i_h)] = CO_kirch_time(filtdata(:,:,i_h), v, h(i_h), dt, dcmp, aper_half, flag_interp);
Kirchhoffdepth(:,:,i_h) = interp1(Skala(:,1),Kirchhofftime(:,:,i_h),Skala(:,i_h),'spline');
z = Skala(:,1);
z_len = length(z);
z_max=max(z);
COG = Kirchhoffdepth;
end
if kirch_depth == 1
[Kirchhoffdepth(:,:,i_h)] = CO_kirch_depth(filtdata(:,:,i_h), v, h(i_h), dt, dz, dcmp, aper_half, flag_interp);
COG = Kirchhoffdepth; %Was schlaueres ueberlegen
end
end
%% CO-Gather for each velocity
mig_graphs('COG',COG(:,:),((1:ns*nh)-1)*dcmp,z,'Depth [km]',sprintf('COGv%g',v))
% Compare max amplitude in each CMP in COG
mig_graphs('OffsetLine',COG,((1:ns)-1)*dcmp,sprintf('ampsv%g',v))
if v == vfinal % If loop reaches the correct velocity (estimated with constant velocity scan)
% (estimated with constant velocity scan)
mig(1:z_len,1:ns) = sum(Kirchhoffdepth,3); % summing CO-Gather
%% Plot of the migration result
mig_graphs('PolarPlot',mig(:,:),((1:ns)-1)*dcmp/1000,z,'CMP [km]','Depth [km]',sprintf('sum_vm%g',v))
% max amplitude of each CMP in migrated section
mig_graphs('SingleLine',max(abs(mig(:,:))),((1:ns)-1)*dcmp,'CMP','Maximum Amplitude','migamp')
%% Calculation of Signal-to-Noise-Ratio
SNRin = log(max(max(filtdata(:,:,1)))/mean(mean(abs(filtdata(100:200,:)))));
SNRorig = log(max(max(abs(data(:,:,1))))/mean(mean(abs(data(100:200,:)))));
SNRout = log(max(max(mig(:,:)))/mean(mean(abs(mig(100:200,:)))));
if kirch_time == 1
% Plot trace 51 normalized
mig_graphs('CompLine','SNR Input',filtdata(:,51,1)/max(filtdata(:,51,1)),'SNR Migriert',mig(:,51)/max(mig(:,51)),((1:nt)-1)*dt,'Zeit [s]','Normalized Amplitude','SNRnorm')
% Plot trace 51 not normalized
mig_graphs('CompLine','SNR Input',filtdata(:,51,1),'SNR Migriert',mig(:,51),((1:nt)-1)*dt,'Zeit [s]','Amplitude','SNRreal')
% Comparison results normalized
mig_graphs('CompLine','Original Data',data(:,51,1)/max(data(:,51,1)),'Migrated Data',mig(:,51,1)/max(mig(:,51,1)),((1:nt)-1)*dt,'Zeit [s]','Normalized Amplitude','waveletNorm')
% Comparison results not normalized
mig_graphs('CompLine','Original Data',data(:,51,1),'Migrated Data',mig(:,51,1),((1:nt)-1)*dt,'Zeit [s]','Amplitude','wavelet')
end
% Output to screen
fprintf('Signal-to-Noise ratio von %f2 (filtered) bzw. %f2 (original) auf %f2\n',SNRin,SNRorig,SNRout)
%% Ergebnis Plots
% Input signal normalized
mig_graphs('CompLine','Original Data',data(:,51,1)/max(data(:,51,1)),'Filtered Data',filtdata(:,51,1)/max(filtdata(:,51,1)),((1:nt)-1)*dt,'Zeit [s]','Normalized Amplitude','inoutNorm')
% Input signal not normalized
mig_graphs('CompLine','Original Data',data(:,51,1),'Filtered Data',filtdata(:,51,1),((1:nt)-1)*dt,'Zeit [s]','Amplitude','inout')
%% Frequency analysis of migrated and summed data
%Use FFT and faxis vectors from above
migdata = fft(mean(mig,2),NFFT)/nt; % FFT of migrated dataset
%% Frequency Plot of migration
mig_graphs('SingleLine',abs(migdata(1:length(faxis)))/max(abs(migdata(1:length(faxis)))),faxis,'Frequencz [Hz]','Normalized Amplitude','freq_mig')
% Frequency Comparison
mig_graphs('CompLine','Original data',abs(fdata(1:length(faxis)))/max(abs(fdata(1:length(faxis)))),'Migrated data',abs(migdata(1:length(faxis)))/max(abs(migdata(1:length(faxis)))),faxis,'Frequency [Hz]','Normalized Amplitude','freq_comp')
% Frequency Comparison
mig_graphs('CompLine','Original data',abs(fdata(1:length(faxis))),'Migrated data',abs(migdata(1:length(faxis))),faxis,'Frequency [Hz]','Amplitude','freq_comp')
% Fileoutput of datamatrices
dlmwrite('output/mig.dat',mig)
dlmwrite('output/COGatherh0.dat',COG(:,:,1));
dlmwrite('output/COGatherh250.dat',COG(:,:,2));
dlmwrite('output/COGatherh500.dat',COG(:,:,3));
dlmwrite('output/COGatherh750.dat',COG(:,:,4));
dlmwrite('output/COGatherh1000.dat',COG(:,:,5));
%%% Für alte Amplitudenvergleiche müsste zurück interpoliert werden, da
%%% z_len != length(t) und z_len hängt von v ab, siehe
%%% t_depth=t_orig*v*0.5;
%%% zmax = max(t_depth); % zmax nimmt mit steigendem v zu, aber
%%% z=0:dz:zmax; % dz bleibt gleich !
end
end
tElapsed = toc(tStart); % calculation time