Abstract

Seismic inversion is applied to generate physical property models (P-wave velocity and numerical attenuation) for four profiles in the Nechako–Chilcotin plateau region of south-central British Columbia, Canada. A newly developed method that combines three-dimensional (3-D) travel-time inversion and 2.5-dimensional (2.5-D) viscoacoustic full-waveform inversion was applied to generate the geophysical models from vibroseis data acquired along the preexisting crooked roads. These models are useful for the characterization of rock types in terms of their positions and thicknesses, which may be used in conjunction with geological ground truth to infer the extent of lithostratigraphic units in the subsurface. The velocity structures also may be used for future reprocessing of the seismic reflection data to derive improved images based on the better near-surface velocity models. The subsurface geology of the Nechako–Chilcotin plateau region is complex, resulting from multiple stages of tectonic compression and extension, contemporaneous with the deposition of sediments and volcanic material. Several basin structures are identified from the joint interpretation of the waveform tomography velocity models and post-stack time migration images. The combination of these results enables the extrapolation and characterization of geological structures to ∼3 km depth, particularly within the Cenozoic volcanic units that dominate near-surface stratigraphy. Based on the seismic profiles, a fence-diagram geological interpretation that extends to ∼3 km depth illustrates the complex structure of the Jurassic to Neogene stratigraphic sequence.

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