Surrey isn't one geological story. South Surrey and White Rock sit on glacial till and Vashon drift, while Newton and Cloverdale hit Fraser River silts and organic deposits just a few meters down. That contrast matters when you're planning a foundation or mapping bedrock. We use seismic tomography to image the subsurface without guessing. Refraction gives us a velocity model for rippability and depth to competent ground. Reflection resolves stratigraphy that refraction misses. A recent project in Clayton Heights needed both methods because a buried channel filled with compressible clay was invisible to standard site investigation. We mapped it in half a day. The MASW survey can complement this when shear wave velocity profiles are required for NBCC site classification.
A velocity contrast doesn't always mean a material change. In Surrey's glacial terrain, it often means a change in density within the same unit.
