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   -> Volume 2, Issue 11


Question: wavelets to analyze seismic signals
 
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Jianxin Wu, (jwu@atlas.nmsu.edu)
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PostPosted: Fri Nov 29, 2002 3:33 pm    
Subject: Question: wavelets to analyze seismic signals
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Question: wavelets to analyze seismic signals

Dear WT experts,

I try to apply WT to analyze seismic signal and would appreciate to obtain
advices for following problems.

(1)Should the coefficients of wavelet transform of a monochromatic wave have
bigger absolute values at the resolution level corresponding to the signal
frequency and smaller at other levels?

(By using the subroutines wt1 and daub4 from Numerical Recipes in C, I
found several coefficients at the resolution level corresponding to the
signal frequency are smaller than other coefficients at same level by
two orders of magnitude.
Furthermore, those coefficients are smaller than ones at adjacent levels.)


(2)Number of WT coefficients varies with resolution level. To obtain
scalogram, the coefficients should distribute over the scale and time
uniformly so that one can make contour plot. How can I interpolate the
coeficients at low resolution levels to have the uniform distribution?

(I use DataPlot which can handle irregular grid to contour the modulus,
the result is not sensible. I think that DataPlot does 2D interpolation,
but we only can interpolate coefficients at same level.)

(3)For DWT, how can I determine f0 in the equation f=f0/a given by Rioul and
Vetterli (1991)?


Jianxin Wu, jwu@atlas.nmsu.edu
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