Imaging complexity in the earth — Case studies with optimized ray tomography

Abstract

When building velocity models for seismic depth imaging, a key tool used in the industry is ray-based tomography. In the past 10 years, the resolution of tomographic solutions has seen a continuous increase because of evolving sophistication in methodologies and technology. A vital issue in the data domain is accuracy and density of residual-moveout picks that are used to derive tomographic velocity-model updates. A new automated method allows for precise tracking of accurate residual moveout on prestack depth-migrated gathers and consequently the fast determination of dense, high-quality traveltime residuals for seismic tomography. Synthetic and real data examples from this method demonstrate the value that accurate information concerning local wave paths inherent in these picks brings to the problem of resolving small-scale velocity anomalies. The determination of such small-scale anomalies ultimately leads to flatter prestack depth-migrated gathers and consequently better-focused structural images.