We propose a new method to isolate the S-wave component of a recorded elastic wavefield
using vertical component seismic data only. The approach is based on the analysis of
spatial seismic wavefield gradients. Spatial gradients are obtained using a finite-difference
approximation between closely-spaced adjacent sources and/or receivers. At the free
surface, the horizontal spatial gradients of the vertical component of the wavefield
correspond to the rotational component of ground motion (curl of the wavefield) around the …