Pure S-waves in land P-wave source VSP data

Abstract

Conventional land vertical seismic profiling (VSP) exploration usually uses P-wave sources and three-component geophones for receivers, emphasizing P-and converted S-waves. Previous studies show that both dynamite borehole shots and vertical vibrations from controllable seismic sources at the surface will produce relatively strong pure P-waves and weaker pure S-waves. Interfaces with a large Poisson's ratio difference have a positive influence on the formation of strong transmitted converted S-waves. By a comparative analysis of pure S-waves from sources and converted downgoing S-waves, we believe that the main frequency of pure S-waves is usually lower than pure P-waves while the main frequency of downgoing converted S-waves is close to that of P-waves. We have studied zero-offset and offset VSP data from land P-wave sources. Results show that pure S-waves commonly exist in these data with differences in wave intensity. S-wave velocity can be obtained from the P-wave source zero-offset VSP data. Finally, we discuss the bright future of joint application of VSP P-and S-waves and the full use of S-waves in P-wave source VSP data.

Estimation of azimuthal anisotropy from VSP data using multicomponent S-wave velocity analysis

“…Most zero-offset VSP surveys are acquired with P-wave sources, which can also generate S-waves (Lash, 1985;Yang et al, 2007). Intensity of these S-waves and their polarization depend on both the type of the source and near-surface heterogeneities.…”