Multicomponent seismic data recorded on the earth's surface provide geologic information useful for natural resource exploration. However, this information is usually altered by propagation through the near-surface layers. In this thesis, effects of the nearsurface layer in multicomponent data are investigated and methods to overcome them are studied. The main effects studied are the free-surface effect, mode-leakage, ray bending, polarization change and statics.
Ray tracing and finite-difference modeling were conducted on basic geologic models and polarization analysis is applied to the results. From this analysis, the free-surface effect appears to have a larger effect at longer offsets, high dips and very high near-surface VP/VS values. Polarization analysis is also carried out on real data obtained from the Blackfoot oil field, Alberta. Horizontally polarized events generated in the near-surface layer are identified. Their polarization direction corresponds well to the actual shotreceiver geometry and, hence, can be used to improve geophone orientation. A method to separate P-P and P-S wave modes taking into account P- and S- wave statics is tested, resulting in improved seismic sections from the Blackfoot survey.
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