Figure 1. In drill-bit seismic technology, the mechanical energy produced by an active rotary-cone drill bit propagates up the drill string to a reference sensor positioned on the swivel and also radiates into the Earth as a seismic wavefield. Seismic events are created that travel direct and reflected raypaths from the drill bit to surface-positioned sensors. A conventional seismic trace is created by continuously correlating the response of the reference sensor at the top of the drill string with the responses of the surface sensors.