A deep-ocean sedimentary velocity function

Seismic events, refracted via sedimentary layers, are seldom seen on refraction profiles from the deep ocean; hence velocities in the sediments must be measured by other means. Velocity at the liquid-sediment interface can be determined from observation of phase changes of wide-angle bottom reflections as seen on long refraction profiles [Fry and Raitt, 1961], and sub-bottom velocities can be computed by applying an X2, T2 solution to deeper reflections from the same profiles. Houtz and Ewing [1963, 1964] combined both methods to derive an empirical formula relating interval velocity to interval time after averaging data from 33 refraction profiles distributed around the North Atlantic Ocean. Use of wide-angle reflections from refraction profiles for velocity studies is not entirely satisfactory for certain technical reasons, not the least of which are the effects of irregular dips along a profile several tens of kilometers long, as well as possible horizon discontinuities.