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COmig.m
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%{
Comig.m - Constant 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
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; % Offset increment [m]
vmin = 1750; % Minimum test velocity [m/s]
vmax = 2150; % Maximum test velocity [m/s]
vfinal = 1950; % Final migration velocity [m/s]
dv = 100; % Velocity increment [m/s]
aper = 120; % Aperturewidth [m]
%% 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);
%% Frequency analysis
NFFT = 2^nextpow2(nt); % calculate next 2^n to prepare Data 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
% Plot of the normalized frequency spektrum
fx = figure(1);
plot(faxis,abs(fdata(1:length(faxis)))/max(abs(fdata(1:length(faxis)))));
xlabel('Frequency','Fontsize',24);
ylabel('Normalized Amplitude','Fontsize',24);
%title('Frequency analysis','Fontsize',24)
set(gca,'Fontsize',24)
set(fx, 'Position', [0 0 1280 1024] ); % Size of the new frame
axis ([0 75 0 1])
print('-dpng','freq.png'); % Outputfile of figure
%% Kirchhoff migration
% Initialising
h = 0:dh:hmax;
Kirchhoffdepth(1:nt,1:ns,1:nh)=0;
i_v = 0;
Kirchhoff(1:nt,1:ns,1:nh)=0; % (time, CMP, offset)
Skala(1:nt,1:nh) = 0;
t=(0:nt-1)'*dt;
i_aper = round(aper/dcmp); % Aperture index
%% Loop over velocities
for v = vmin:dv:vmax;
i_v = i_v+1;
Kirchhoff(1:nt,1:ns,1:nh)=0; %(time, CMP, offset)
Skala(1:nt,1:nh) = 0;
%% loop over half offsets
for i_h = 1:nh
[Kirchhoff(:,:,i_h), Skala(:,i_h)] = CO_kirch(filtdata(:,:,i_h), v, h(i_h), dt, dcmp, i_aper);
Kirchhoff([1 end-5:end],:,i_h) = 0; % Filter side effects
Kirchhoffdepth(:,:,i_h) = interp1(Skala(:,1),Kirchhoff(:,:,i_h),Skala(:,i_h),'spline');
end
% CO-Gather for each velocity
fx=figure(v);
set(fx, 'Position', [0 0 1280 1024] );
imagesc(((1:ns*nh)-1)*dcmp,Skala(:,1)/1000,Kirchhoffdepth(:,:),[-max(max(max(abs(Kirchhoffdepth)))) max(max(max(abs(Kirchhoffdepth))))])
%title('Tiefenmigration','Fontsize',24)
xlabel('CMP [km]','Fontsize',24)
ylabel('Depth [km]','Fontsize',24)
set(gca,'Fontsize',24)
colormap([ones(101,1),(0:.01:1)',(0:.01:1)';(1:-.01:0)',(1:-.01:0)',ones(101,1)]) % polarized plot
colorbar
set(gca,'Fontsize',24)
set(gca,'XTickMode','manual')
set(gca,'XTick',[0;2000;4000;6000;8000;10000])
set(gca,'XTickLabel',[' 0 ';'2 / 0';'2 / 0';'2 / 0';'2 / 0';' 2 ']) % rescaling x-axis
print('-dpng',sprintf('v%g.png',v));
if v == vfinal % If loop reaches the correct velocity (estimated with constant velocity scan)
mig(1:nt,1:ns) = sum(Kirchhoffdepth,3); % summing CO-Gather
% Plot of the migration result
fx=figure(v+1);
set(fx, 'Position', [0 0 1280 1024] );
imagesc(((1:ns)-1)*dcmp/1000,Skala(:,1)/1000,mig(:,:),[-max(max(abs(mig))) max(max(abs(mig)))])
%title('Tiefenmigration','Fontsize',24)
xlabel('CMP [km]','Fontsize',24)
ylabel('Depth [km]','Fontsize',24)
colormap([ones(101,1),(0:.01:1)',(0:.01:1)';(1:-.01:0)',(1:-.01:0)',ones(101,1)])
colorbar
set(gca,'Fontsize',24)
print('-dpng',sprintf('sum_v%g.png',v));
% Plot trace 51 normalized
figure
plot(((1:nt)-1)*dt,filtdata(:,51,1)/max(filtdata(:,51,1)),'r')
hold on
plot(((1:nt)-1)*dt,mig(:,51)/max(mig(:,51)),'k')
ylabel('Normalisierte Amplitude','Fontsize',24)
xlabel('Zeit [s]','Fontsize',24)
legend('SNR Input','SNR Migriert','Location','NorthWest')
set(gca,'Fontsize',24)
print('-dpng','SNRnorm.png');
% Plot trace 51 not normalized
figure
plot(((1:nt)-1)*dt,filtdata(:,51,1),'r')
hold on
plot(((1:nt)-1)*dt,mig(:,51),'k')
ylabel('Amplitude','Fontsize',24)
xlabel('Zeit [s]','Fontsize',24)
legend('SNR Input','SNR Migriert','Location','NorthWest')
set(gca,'Fontsize',24)
print('-dpng','SNRreal.png');
% Calculation of Signal-to-Noise-Ratio
SNRin = log(max(max(filtdata(:,:,1)))/mean(mean(abs(filtdata(100:200,:)))));
SNRout = log(max(max(mig(:,:)))/mean(mean(abs(mig(100:200,:)))));
fprintf('Verbesserung der Signal-to-Noise ratio von %f2 auf %f2\n',SNRin,SNRout)
%Input signal normalized
figure
plot(((1:nt)-1)*dt,filtdata(:,51,1)/max(filtdata(:,51,1)),'r')
hold on
plot(((1:nt)-1)*dt,data(:,51,1)/max(data(:,51,1)),'k')
ylabel('Normalisierte Amplitude','Fontsize',24)
xlabel('Zeit [s]','Fontsize',24)
legend('Filtered data','Original data','Location','NorthWest')
set(gca,'Fontsize',24)
print('-dpng','inoutNorm.png');
%Input signal not normalized
figure
plot(((1:nt)-1)*dt,filtdata(:,51,1),'r')
hold on
plot(((1:nt)-1)*dt,data(:,51,1),'k')
ylabel('Amplitude','Fontsize',24)
xlabel('Zeit [s]','Fontsize',24)
legend('Filtered data','Original data','Location','NorthWest')
set(gca,'Fontsize',24)
print('-dpng','inout.png');
%Comparison results normalized
figure
plot(((1:nt)-1)*dt,mig(:,51,1)/max(mig(:,51,1)),'r')
hold on
plot(((1:nt)-1)*dt,data(:,51,1)/max(data(:,51,1)),'k')
ylabel('Normalisierte Amplitude','Fontsize',24)
xlabel('Zeit [s]','Fontsize',24)
legend('Migration result','Original data','Location','NorthWest')
set(gca,'Fontsize',24)
print('-dpng','waveletNorm.png');
%Comparison results not normalized
figure
plot(((1:nt)-1)*dt,mig(:,51,1),'r')
hold on
plot(((1:nt)-1)*dt,data(:,51,1),'k')
ylabel('Amplitude','Fontsize',24)
xlabel('Zeit [s]','Fontsize',24)
legend('Migration result','Original data','Location','NorthWest')
set(gca,'Fontsize',24)
print('-dpng','wavelet.png');
% Fileoutput of datamatrices
dlmwrite('mig.dat',mig)
dlmwrite('COGatherh0.dat',Kirchhoffdepth(:,:,1));
dlmwrite('COGatherh250.dat',Kirchhoffdepth(:,:,2));
dlmwrite('COGatherh500.dat',Kirchhoffdepth(:,:,3));
dlmwrite('COGatherh750.dat',Kirchhoffdepth(:,:,4));
dlmwrite('COGatherh1000.dat',Kirchhoffdepth(:,:,5));
end
end