P-wave anisotropy of the Pierre Shale

Experimental evidence for the existence, at seismic frequencies, of transverse isotropy with a vertical symmetry axis is not overwhelming. Anisotropy of this type has been inferred for SH‐waves from a consistent overestimation of reflector depths. Because of the shape of transverse isotropy velocity surfaces for P‐waves and the accompanying tendency to obtain vertical velocities (Krey and Helbig, 1956), only a few field measurements of P‐wave anisotropy are in the literature.