LAB 04 - DECONVOLUTION SHOT 1 TO 18

MATLAB SCRIPT LAB 4.2

clear,clc,close all
load SeismicData_gain_bpf_C

%% Extracting shots and geometry acquisition parameters
shot_num=1:18;
p=1;
[Dshot,dt,dx,t,offset]=extracting_shots(Dbpf,H,shot_num,p);
[nt,nx]=size(Dshot);

%% Before Applying Spiking deconvolution
scale=1;
figure(1);
mwigb(Dshot,scale,offset,t)
xlabel('Trace number','FontSize',14)
ylabel('Time(s)','FontSize',14)

Figure 1: shot gathers no 1-18 before applying spiking deconvolution

%% Apply auto-correlogram function
max_lag=0.2;
[Dauto,lags]=auto_correlation_map(Dshot,max_lag,dt);

%% Display auto-correlogram
scale=5;
figure(2);
mwigb(Dauto,scale,offset,lags)
xlabel('Trace number','FontSize',14)
ylabel('Time lag(s)','FontSize',14)

Figure 2: auto-correlogram of shot gathers 1-18

%% Applying Spiking deconvolution
mu=0.1;
Ds=spiking_decon(Dshot,max_lag,mu,dt);

%% Display After Applying Spiking deconvolution
scale=1;
figure(3)
mwigb(Ds,scale,offset,t)
xlabel('Trace number','FontSize',14)
ylabel('Time(s)','FontSize',14)

Figure 3: shot gathers 1-18 after applying spiking deconvolution​

%% Generate the Normalised PSD
Davg_before=mean(Dshot');
fs=1/dt;
[Davg_before,b4_f]=periodogram(Davg_before,[],2*nt,fs);
Davg_before=Davg_before/max(Davg_before);
Davg_before=20*log10(abs(Davg_before));

Davg_after=mean(Ds');
[Davg_after,af_f]=periodogram(Davg_after,[],2*nt,fs);
Davg_after=Davg_after/max(Davg_after);
Davg_after=20*log10(abs(Davg_after));

f=linspace(-0.5,0.5,2*nt)/dt;
figure,plot(b4_f,Davg_before,af_f,Davg_after,'r--')
xlabel('Frequency(Hz)','FontSize',14)
ylabel('Normalised PSD','FontSize',14)
grid
legend('Before Decon','After Decon')

Figure 4: PSD of the average trace of shot gathers 1-18 before and after spiking deconvolution

%% Apply gain

agc_gate=0.5;

T=2;

Ds_gain=AGCgain(Ds,dt,agc_gate,T);

%% Save

clear af_f b4_f Dauto Davg_after Davg_before Dbpf Dshot dt dx f fs lags max_lag mu nt nx offset p scale shot_num t T agc_gate Ds

save SeismicData_gain_bpf_sdecon_gain_C

To further enhance the result before sorting the data to the next chapter, you need to apply instantaneous AGC with window length of 0.5 s to the deconvolved data. We applied AGC to compensate for the lost amplitudes after deconvolution.