Velocity analysis using weighted semblance

Abstract

Increasing the resolution of semblance-based velocity spectra, or semblance spectra, is useful for estimating normal moveout velocities, as increased resolution can help to distinguish peaks in the spectra. The resolution of semblance spectra depends on the sensitivity of semblance to changes in velocity. By weighting terms in the semblance calculation that are more sensitive to changes in velocity, we can increase resolution. Our implementation of weighted semblance is a straightforward extension of conventional semblance. Somewhat surprisingly, we increase resolution by choosing an offset-dependent weighting function that minimizes semblance. We test our method on synthetic and field data, and our tests confirm that weighted semblance provides higher resolution than conventional semblance.