In Saint John, many project sites sit on a complex mix of glacial till overlying fractured bedrock, and what you see at surface rarely tells the whole story. We've worked on plenty of jobs where a conventional borehole hit refusal at three meters, but the neighboring lot had a buried channel filled with soft silts extending twice that depth. Seismic tomography cuts through that guesswork by mapping the velocity structure of the subsurface in two dimensions, which lets you see how competent the rock actually is and where the transitions happen. For developers dealing with the city's sloping terrain north of the Reversing Falls, this kind of continuous profile is far more useful than point data alone. We often recommend pairing the tomography grid with a few targeted test pits to ground-truth the velocity boundaries against visible soil strata, especially in areas where the Wisconsinan till is thin and the underlying Cambrian metasediments are highly variable.
A velocity tomogram doesn't just show you where the bedrock is—it shows you whether that bedrock is worth building on.
