Association of State Boards of Geology ASBOG 1 Practice Exam

Seismic refraction relies on differences in how fast seismic waves travel through different rocks. When a wave moves from a layer with slower velocity into one with faster velocity, it bends at the interface and a portion travels along or near the boundary. This velocity contrast creates characteristic travel-time patterns measured at the surface, and from those patterns you infer where interfaces lie and how deep they are. In short, layering is revealed by changes in seismic velocity between layers.

Other properties don’t govern this method: ground conductivity is an electromagnetic property, not related to how seismic waves propagate; the thermal gradient affects heat flow rather than wave speeds; and magnetic susceptibility concerns magnetic properties, not seismic refraction signals.