function c=ricker(dt,pt)
% RICKER generate a ricker wavelet
% input (dt,period)

nt=2*pt/dt;
c=1:nt;
c=c*0;

        t0=pt/dt;
        a_ricker=4/pt;

for it=1:nt
            t=(it-t0)*dt;c(it) = exp(-(a_ricker*t)^2);
end



