Most of our Q-estimation investigations in previous work are based on the analytical signal method. Surprisingly large Q-factors at shallow depths had been observed for a Ross Lake VSP. In this report we are comparing the analytical signal approach to the spectral ratio method for two different VSP data sets. The two Q-estimation methods compare well when equal depth intervals are chosen for the analysis. Stratigraphic (apparent) Q appears to dominate the estimated "Q versus depth" functions in both VSP locations.
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