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How to convolve a wavelet with a signal to make a wedge model?

조회 수: 4 (최근 30일)
Maria Amr
Maria Amr 2021년 1월 27일
답변: Afshin Aghayan 2021년 1월 27일
I asked my question in public but I have not got any help. I would appreciate if you can help me as I am new in MATLANB :(.
I have a signal and I want to convolve it with a wavelet and make a wedge model. It is a seismic wedge model and I want to make a single low impedance layer wedge model. I truly appreciated in advance!
My wavelet code is:
%.............................................
fr=30;% frequency
dt=.002;
T=0.1;
tt=-T:dt:T;
tsh=0.008;%time shifting
tr=round(length(tt)/2);
t=tt(tr:end);
zpr=(1-tt.^2*fr^2*pi^2).*exp(-tt.^2*pi^2*fr^2);%zero-phase ricker
figure(10)
plot(zpr)
%................................................
My signal is:
%...............................................
data=xlsread('1');
amp=data(:,2);%us/f
time=data(:,1);%ms
tim=time(1:1:end);
am=amp(1:1:end);
len=length(tim);
for i=1:len
if am(i)==-999.25
am(i)=am(i-1);
end
end
data1=zeros(len,2);
tti=round(tim);
for j=2:len
r(j)=(am(j)-am(j-1))/(am(j)+am(j-1));% reflection coefficients
end
plot(r)
%%%%%%%%%
I can convolve the wavelet and signal to make a simple synthetic trace but not a wedge.
%..............................................................
s=conv(r,zpr);
if mod(length(zpr),2)==0
s=s(length(zpr)/2:end-length(zpr)/2);
else
s=s((length(zpr)-1)/2:end-(length(zpr)-1)/2);
end
ls=length(s);
s(ls)=[];
[m1 n1]=size(s);
if m1==1
s=s';
end
n=10;
dx=2;
scal=5;
figure(1)
for i=1:n
b=(i-1)*dx;
a=scal*s+b;
c=a;
a(a<b)=b;
plot(c,tti,'black')
hold on
fill(a,tti,'k','linestyle','none');
end
hold off
set(gca,'YDir','reverse')
xlim([-dx (n+1)*dx])
ylim([700 2826])
ylabel('millisecent')
title('synthetic trace made of zero-phase ricker') ;

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Afshin Aghayan
Afshin Aghayan 2021년 1월 27일
I wrote the following code a long time ago (2011) that can create seismic events based on their slope like wedge model. I hope it can be useful for you.
% This function diplays siemic events based on slope
clc
number=input('How maney events do you want to see? ');
x=input('Enter number of traces : ');
d=input('Enter trace interval in m : ');
t=input('Enter maximum recording time in ms : ');
f=input('Enter frequency of the Ricker wavelet (Hz) : ');
% Ricker wavelet equal ricker=(1-2(pi*f*t)^2)*exp(-(pi*f*t)^2))
n=(0:100);
wavelet=(1-2*(pi*f*(n-50)*0.001).^2).*exp(-(pi*f*(n-50)*0.001).^2);
% Creating the impedance matrix
ImpMatrix=zeros(t,x);
for num=1:number
slope=input(['Enter slope of the event#' num2str(num) ' in degree (e.g. 0 means horizontal line) : ']);
t0=input(['Enter start time of the event#' num2str(num) ' in ms : ']);
if t0==0; t0=1; end % In the case t0=0, we assume that the event is recorded at the first sample
for i=1:x
k=d*i;
t1=k*tand(slope)+t0;
if ceil(t1)<=t && ceil(t1)>0
ImpMatrix(ceil(t1),i)=1;
end
end
end
fieldCon=conv2(ImpMatrix,wavelet','same');
field=fieldCon(1:t,:);
%================================Display===================================
if exist('wigb') == 2 % check wigb function exists
figure, wigb(field);
ylabel('Time (ms)'), xlabel('Trace no.')
ylim([1 t])
end
figure,imagesc(field)
ylabel('Time (ms)'), xlabel('Trace no.')
% Afshin Aghayan
% 2011

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