Processing of ground roll for the study of near-surface Rayleigh wave dispersion

Andrew Mills and Kris Innanen

ABSTRACT

In investigations of the generation of dispersion curves from shot records, it was noted that as receiver spacing increased, aliasing noise and other artefacts in the tau-p domain increased. This resulted in shear wave velocity dispersion curve "noise", which masked the true dispersion curve. The purpose of this study is to test whether interpolation of ground roll in synthetic shot records can reduce the tau-p aliasing from sparsely sampled shot records, and as a result improve the generated dispersion curves.

Synthetic shot records are generated at varying receiver spacings, then two methods of processing are tested and compared. Processing of raw shot records to isolate ground roll followed by interpolation, and interpolation of raw shot records followed by processing to isolate ground roll. Dispersion spectrum noise is reduced or eliminated at low frequencies with both methods. However, when interpolation follows processing, the maximum detectable dispersion curve frequency is less than for the reverse process. This reverse process achieves an equivalent result to the original 10m receiver spacing dispersion spectra at frequencies below 35Hz.

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