Seismic reflection profile of the Newark basin. Seismic profiling using sound waves to determine subsurface geology , much like an X-ray uses radiation to "see" inside the human body. Sound waves bounce off the boundaries between different rock types to produce reflections. The NB-1 seismic line is located to the southwest of the Delaware River (map above). In the middle diagram, a basic interpretation is superimposed on the seismic line showing the geometry of reflections (alternating black and white "lines"); faults are shown in red, and formation boundaries are the thin, colored lines. The complete geologic interpretation is shown in the lower diagram. Click on all diagrams to see larger versions. Modified from Withjack et al. (1998) and Withjack et al. (2002).