Near-surface characterization using seismic refraction and surface-wave methods

Varying thicknesses and velocities of near-surface layers cause serious problems for seismic reflection imaging of the deeper subsurface. Static corrections, calculated from near-surface velocity models, are used to remove the effects of the variable topographic near surface. In this thesis, near-surface layers are studied and characterized using two methods: Generalized Linear Inversion (GLI) of first arrival times and Multichannel Analysis of Surface Waves (MASW). The first is a widely used and proven method for obtaining near-surface velocity models for both P and S waves. The second is mainly used for geotechnical engineering purposes and is based on the dispersion properties of Rayleigh waves.;Two sites (at the Rothney Observatory and Spring Coulee, Alberta) are investigated. In the Rothney case, the S-wave velocities of the near surface (obtained by the MASW method) range from 200 to 1200 m/s and roughly correlate to the lithology log of a well drilled on site. In Spring Coulee, the S-wave near-surface models (obtained by GLI of first arrival times method) had different velocity layering and base of weathering from those of P waves. The MASW S-wave velocity model of Spring Coulee, Alberta correlates well to the GLI model. P-wave velocities range from 900 to 3600 m/s, while S-wave velocities range from 420 to 1966 m/s. Static corrections are calculated using near-surface models and are applied prior to stacking of PP and PS data. P-wave static corrections range from -25 ms to 27 ms, and those for S-wave range from -65 ms to 12 ms.