Seismic Velocity Structure Beneath the Tofino Forearc Basin Using Full Waveform Inversion

Given the effects of steep dips and large lateral variations in seismic velocity beneath Vancouver Island continental shelf, processing travel time inversion are inadequate to obtain a detailed model subsurface. Therefore, full waveform is applied multichannel reflection data high-resolution Tofino fore-arc basin under shelf off margin. Seismic velocities obtained this study help understanding shallow sediment structures, as well deeper structures associated with accreted terranes, such Pacific Rim Crescent terranes. Shallow high velocities, ∼5 km/s, were modeled mid-shelf region at ∼1.5–2.0 km depth. These coincide an anticlinal structure data, possibly indicate shallowest occurrence volcanic terrane. In general, increase landward, indicating over-consolidation related compressional regime ongoing subduction Juan de Fuca plate emplacement show sharp about 10 west Island, underlying transition A prominent low zone extending over observed 800–900 m below seafloor. This indicates presence porosity layer lithology changes. Alternatively, may fluid over-pressure or over-pressured gas potential hydrocarbon environment.