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Introduction

Kirchhoff migration is generally accepted to be the most efficient method of imaging 2-D and 3-D prestack seismic data. The Marmousi synthetic data set (Versteeg, 1994) has been a popular testbed for migration algorithms and many researchers have discovered that Kirchhoff algorithms using first-arrival traveltimes do a poor job of imaging the target zone (Gray and May, 1994; Audebert et al., 1994; Geoltrain and Brac, 1993). Even methods which calculate most energetic arrivals and estimate amplitude and phase do not always result in images which compare favorably with finite-difference shot-profile migration.

In their 1993 Geophysics article, Geoltrain and Brac ask the question ``Can we image complex structures with first-arrival traveltime?'' They conclude that they cannot, and that they should either ray trace to find the most energetic arrivals, or calculate multiple-arrival Green's functions. Nichols (1994) calculates band-limited Green's functions to estimate the most energetic arrivals. He estimates not only traveltime, but also amplitude and phase. My approach is simpler; by breaking up the complex velocity structure, I am able to calculate traveltimes in velocity models where finite-differencing the eikonal equation is valid. This results in images comparable to those obtained by Nichols' method and by shot-profile migration at a reduced computational cost.

Like most of the other researchers in the field, I test my method on the ever-popular Marmousi synthetic.


next up previous [pdf]

Next: TRAVELTIME CALCULATION Up: Bevc: Imaging complex structures Previous: Bevc: Imaging complex structures

2013-03-03