Angle-dependent attenuation estimates from a walk-away VSP

Effective seismic attenuation may vary as a function of propagation angle both because of anisotropy in the intrinsic attenuation and because of angle-dependent apparent attenuation due to scattering. We develop a methodology for estimating angle-dependent attenuation, and analyze data recorded in a walk-away (WA-) VSP experiment on the Western Shelf of Australia. Results indicated waves traveling at large angles of propagation experience significantly higher levels of attenuation than those traveling at near vertical incidence. For the largest angle of propagation in our dataset (close to 45°), attenuation appeared over 50% higher on both orthogonal shooting directions. This is consistent with elastic modeling results.