Estimation of shear-wave interval attenuation from mode-converted data

Interval attenuation measurements provide valuable information for reservoir characterization and lithology discrimination. We extend the attenuation layer-stripping method of Behura and Tsvankin to mode-converted (PS) waves with the goal of estimating the S-wave interval attenuation coefficient. By identifying PP and PS events with shared ray segments and applying the PP+PS=SS method, we first perform kinematic construction of pure shear (SS) events in the target layer and overburden. Then, the modified spectral-ratio method is used to compute the effective shear-wave attenuation coefficient for the target reflection. Finally, application of the dynamic version of velocity-independent layer stripping to the constructed SS reflections yields the interval S-wave attenuation coefficient in the target layer. The attenuation coefficient estimated for a range of source-receiver offsets can be inverted for the interval attenuation parameters. The method is tested on multicomponent synthetic data generated with the anisotropic reflectivity method for layered VTI (transversely isotropic with a vertical symmetry axis) and orthorhombic media.