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I sincerely thank. My great amigo. Zoli. for being Zoli. I sincerely thank. this amigo. and. this amigo. for the kind invite. I wish to, humbly and most sincerely, thank the. The Society that publishes 2 of the very best. and holds meetings in exotic places.
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I sincerely thank My great amigo Zoli for being Zoli
I sincerely thank this amigo and this amigo for the kind invite
This tour would have been a rout without Judy Wall who organised it ALL !!! Imagine. Angels do exist in the sky.
With additonal thanks to Tury Taner, what can I say?, he who has done it all. Enders Robinson, he was and is, numero uno. Sven Treitel, there are no words, except, Sven. Arthur Weglein, my friend, my teacher. Mauricio Sacchi, without whom Tad would be Tad who? Those marvelous friends, colleagues, students, who must assume full responsibility for making me who I have become.
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and now the taaaalk
The role of AmplitudeandPhasein Processingand InversionTadeusz Ulrych
I have chosen this title, because I can talk about ANYTHING !!
This presentation was prepared while partying in the local bar, illustrated in the next slide
A brief story Doug Foster arranges a presentation for Monday Dr. Doug J. Foster This is Me Sunday evening is slightly brutal I cannot remember [1] How many participants? [2] Where is my presentation? I have a Canadian cell with enough credit for ONE question
What question do I ask? How many participants? or Where is the presentation?
The answer to HOW MANY? is AMPLITUDE (goodbye presentation and future invitation)
The answer to WHERE? is PHASE (Oblivious to the number, I blindly carried on)
WHERE ? HOW BIG ? x
? Original
INTRODUCTION • Mathematics is Beautiful. • However, it is tiresome to digest. • Therefore, this talk contains aslittle of this beauty as possible. • Please remember, that the magic of mathematics lies in its physical interpretation. For example ….
Question Why is it true that = (-1)1/2 x
Because, as is well known (-1)1/2 = i and i is an operator that rotates by 90o
Amplitude & Phase in blind deconvolution The Enders example
The Man Enders Robinson
The canonical model for the seismogram is the seismogram is the source signature is the Greens function, the reflectivity is ‘everything else’, the noise
This equation, is 1 equation with 2 unknowns. This is akin to 7= a + b and what is a and b uniquely ?
This, of course, is an impossible problem unless a priori constraints are known or, at least, assumed
THIS IS A YOU Some more thoughts regarding Phase
OUTLINE for the next few slides • POCS and only-phase reconstruction • Phase and cepstral processing • Summary
POCS Projection onto convex sets POCS attempts to solve an underdetermined, generally nonlinear, inverse problem G[x]+n=d where G is a nonlinear operator
A convex set, A, is one for which the line joining any two points, x and y, in the set, is totally within the set. In other words, a set A in a vector space is convex, iff x and y Є A λx + (1 - λy) Є A 0 ≤ λ ≤ 1
Illustrating convex and non-convex sets A convex setA non-convex set
Alternating POCS Iterative projection onto convex sets
Possible stagnation point when one of the sets is non-convex
Application of alternating POCS to the problem of reconstruction from phase-only to obtain the only-phase image
The image, of finite support , is a convex set. The set of constraints, the thresholded image, is also another convex set.
Phase in Cepstral analysis Phase is fundamental in cepstral processing • Phase must be unwrapped • Phase must be detrended • A serious problem is additive noise
The cepstrum (complex) is defined as C(n) = {ln[A(ω)] + iΦ(ω)} where is the inverse Fourier transform
Application of cepstral analysis to • thin bed blind deconvolution • Compute cepstrum for each trace • Stack the cepstra • Transform back to the time domain • Deconvolve with estimated wavelet