Shear-wave vibrator signals in transversely isotropic shale

The experiments of Robertson and Corrigan (1983) on shale are among the first three-component field observations of shear waves in transversely isotropic media to be published. Their data are reprocessed to highlight the effects of the shale's anisotropy on shear waves. Two results emerge. First, shear-wave splitting in a transversely isotropic substrate is most easily observed when the vibrator baseplate is oriented so that both SH- and SV-waves reach the geophone. Second, the SV-wave polarization deviates significantly from perpendicular to the raypath. Both results may significantly affect the interpretation. Both are found to agree with theoretical results and are modeled successfully by synthetic seismograms.