f Shear wave propagation in thinly layered media - Observations on VSP data from a test site

Several examples of determinations of shear wave velocities from multi-offset VSP surveys are available in the literature. Mostly these were done in regions where the lithological units could be assumed to be homogeneous over several tens of metres at least. We present some features of shear wave propagation that we have observed from a VSP survey carried out at a borehole test site in Whitchester in northern England. The boreholes at the site have been extensively logged and an important difference between other reported surveys and ours is that the sonic log indicates a lithology with significant velocity variations even at depth scales of a few centimetres.